Verlet physics applied to a simple car model.

Disclaimer: this code is not even close to finished. Dozens of things need to fixed/improved. I decided to put it up anyways because it will be weeks before I have the time to finish it. I works well enough to demonstrate how verlet physics can be applied to a real world object.

;work in progress!!!!!
;its not optimized, friction is not completed, and about a dozen other things arent finished.
;just putting this out there because its going to be weeks before i can finish these things.

Graphics3D HEIGHT,WIDTH,16,2
Const FPS=30
Const HEIGHT=640					; graphics width
Const WIDTH=480					; graphics height
Const ACTIVE=1					; collision type
Const VERLET=2					; collision Type
Const FRONT_TIRE=0				; Vobject part name
Const REAR_TIRE=1					; Vobject part name
Const BODY=2						; Vobject part name
Const CENTER=3					; Vobject part name
Const SIZE#=8					; just a multiplier for how big the Vobject will be
Const ITERATIONS = 2				; How many loops through the "relaxation" routine, Lower = speed up / lose accuracy
Global DeltaTime#					; Time between physics calculations
Global vGrav.Vector = Vector(0.0,9,0.0)	; Gravity. yes i know its a positive value. still dont know why this is but it works.
Global vTemp1.Vector = Vector(0,0,0)	; Some temporary vectors for calculations
Global vTemp2.Vector = Vector(0,0,0)
Global world_friction#=0				; air resistance
Global temp_turn#=0
Global traction#=0
Global roll#
front_stiff=20						; This is actually the mass value for the front wheel. lower mass = less stiff. caution will collapse
rear_stiff=30						; This is actually the mass value for the rear wheel. lower mass = less stiff. caution will collapse

Type Vector
	Field x#
	Field y#
	Field z#
End Type

Type VerletPack							
	Field start_loc.vector					; Defines where this verlet started at so we can fix it when it gets to far out of place
	Field current.Vector						; Current position
	Field old.Vector						; Last position
	Field gravity.Vector						; Accumulated forces
	Field radius#							; Collider radius
	Field mass.vector						; Point mass of this particular verlet
	Field entity							; Pivot assigned to this verlet for both position and collision
	Field mesh							; Mesh assigned to this verlet if any such as wheels or body parts
	Field part								; Describes what verlet represents. example wheel or body part.
	Field state							; Collideable status true/false	
	Field contact_friction#					; When in contact with the ground how much friction is applied
End Type

Type Constraint							; Two verlets connected by a mutual spring
	Field v1.VerletPack						; First verlet
	Field v2.VerletPack						; Second verlet
	Field d#								; Distance between verlets
End Type

Type Vobject								; This is the parent object that the verlets are associated with
	Field v.VerletPack[8]					; The array of individual verlets
	Field num_verlets						; Total number of verlets (array dim value)
	Field player_pivot						; Pivot used to represent player. this pivot is dynamically controlled by player.
	Field player							; Mesh used to represent the player. this mesh is parented to player_pivot
	Field center.VerletPack					; Used to position player_pivot but not neccessarily parented to.
	Field x1.VerletPack						; x1 and x2 are used to define a vector left/right to align player_pivot
	Field x2.VerletPack
	Field z1.VerletPack						; z1 and z2 are used to define a vector forward/aft to align player_pivot
	Field z2.VerletPack
	Field X_vec#							; vectors for calculations
	Field Y_vec#
	Field Z_vec#
	Field mass#							; Mass for physics calculation on entire Vobject
	Field horsepower#						; Force for physics calculations on entire Vobject
	Field acceleration#						; Rate at which the Vobject accelerates
	Field velocity#							; Velocity of entire Vobject
	Field distance#						; Distance Vobject has travelled
	Field position#							; Position is the distance accumulator
End Type

;***** make the vehicle ****************************************
	tempx# = 0							;start location of vehicle
	tempy# = 20							;start location of vehicle
	tempz# = 150							;start location of vehicle
	Global car.Vobject = New Vobject 			;initialize the Vobject type
	car\player_pivot=CreatePivot()			;this is the master pivot that the player will contol
	car\player=CreateCube(car\player_pivot)	;mesh that is assigned to player_pivot. in this case a simple cube for a car body
	ScaleEntity car\player, 15,6,30			;get car body into postion and scaled etc
	EntityColor car\player, 255,0,0
	PositionEntity car\player, 0, 2, -6
	car\num_verlets = 8						;total number of verlets in the Vobject. count from zero
	car\mass=10							;this mass value is used for physics calculations on player_pivot.
	car\horsepower = 200					;the force exerted on player_pivot
	sx# = 1.9								;just a multiplier for the Vobject size
	sy# = 1.2								;just a multiplier for the Vobject size
	sz# = 2.65							;just a multiplier for the Vobject size
	
	;parameters   x,y,z,radius, mass, part,mesh,state,collision_type, contact_friction
	a.VerletPack = Verlet(tempx - SIZE * sx, tempy - SIZE * sy, tempz - SIZE * sz,  7, front_stiff, FRONT_TIRE, CreateCylinder(12), True, VERLET, 0)
	b.VerletPack = Verlet(tempx + SIZE * sx, tempy - SIZE * sy, tempz - SIZE * sz, 7, front_stiff, FRONT_TIRE, CreateCylinder(12), True, VERLET, 0)
	c.VerletPack = Verlet(tempx + SIZE * sx, tempy + SIZE * sy, tempz - SIZE * sz, 7, 400.0, BODY, 0, True, VERLET, 0)
	d.VerletPack = Verlet(tempx - SIZE * sx, tempy + SIZE * sy, tempz - SIZE * sz, 7, 400.0, BODY, 0, True, VERLET, 0)
	e.VerletPack = Verlet(tempx - SIZE * sx, tempy - SIZE * sy, tempz + SIZE * sz, 9, rear_stiff, REAR_TIRE, CreateCylinder(12), True, VERLET, 0)
	f.VerletPack = Verlet(tempx + SIZE * sx, tempy - SIZE * sy, tempz + SIZE * sz, 9, rear_stiff, REAR_TIRE, CreateCylinder(12), True, VERLET, 0)
	g.VerletPack = Verlet(tempx + SIZE * sx, tempy + SIZE * sy, tempz + SIZE * sz, 7, 400.0, BODY, 0, True, VERLET, 0)
	h.VerletPack = Verlet(tempx - SIZE * sx, tempy + SIZE * sy, tempz + SIZE * sz, 7, 400.0, BODY, 0, True, VERLET, 0)
	i.VerletPack = Verlet(tempx, tempy + 5, tempz + 8, 7, 400.0, CENTER, 0, False, VERLET, 0)
	
	; Edges
	Constraint2(a,b)
	Constraint2(b,c)
	Constraint2(a,d)
	Constraint2(c,d)
	Constraint2(e,f)	
	Constraint2(f,g)
	Constraint2(e,h)
	Constraint2(g,h)
	Constraint2(a,e)
	Constraint2(b,f)
	Constraint2(c,g)
	Constraint2(d,h)

	; Cross-faces
	Constraint2(a,c)
	Constraint2(b,d)
	Constraint2(e,g)
	Constraint2(f,h)
	Constraint2(a,f)
	Constraint2(a,h)
	Constraint2(b,e)
	Constraint2(b,g)
	Constraint2(c,f)
	Constraint2(c,h)
	Constraint2(d,e)
	Constraint2(d,g)

	; Diagonals
	Constraint2(a,g)
	Constraint2(b,h)
	Constraint2(c,e)
	Constraint2(d,f)
	
	; Constraining the center sphere
	Constraint2(a,i)
	Constraint2(b,i)
	Constraint2(c,i)
	Constraint2(d,i)
	Constraint2(e,i)
	Constraint2(f,i)
	Constraint2(g,i)
	Constraint2(h,i)

	; Assign individual verlets to the array	
	car\v[0] = i
	car\v[1] = a
	car\v[2] = b
	car\v[3] = c
	car\v[4] = d
	car\v[5] = e
	car\v[6] = f
	car\v[7] = g
	car\v[8] = h
	
	; assign a verlet the center position
	car\center=i
	; Set up variables used for player mesh/pivot aligntovector. one is left to right, other is forward back.
	car\x1=c
	car\x2=d
	car\z1=g
	car\z2=c
	
	PositionEntity car\player_pivot, EntityX(car\center\entity),EntityY(car\center\entity),EntityZ(car\center\entity)
;Next
;***********************************************************************************************

measure_pivots(car.Vobject, 0)

;ClearTextureFilters
;SetBuffer BackBuffer()
Collisions VERLET,ACTIVE,2,2
MoveMouse WIDTH/2,HEIGHT/2

lgt = CreateLight()
LightColor lgt,300,300,300
RotateEntity lgt,35,0,0
AmbientLight 94,94,80
Global cam = CreateCamera()
CameraFogMode cam,0
CameraFogColor cam,128,128,180
CameraClsColor cam,128,128,180
CameraRange cam,1,4000
CameraFogRange cam,500,3000
CameraZoom cam,1


bump=CreateCylinder(4)
ScaleEntity bump, 5,600,20
RotateEntity bump,0,0,90
EntityType bump, ACTIVE
EntityColor bump,0,255,0
PositionEntity bump,0,0,-500
PositionEntity CopyEntity(bump),0,0,-600
PositionEntity CopyEntity(bump),0,0,-700
PositionEntity CopyEntity(bump),0,0,-800
PositionEntity CopyEntity(bump),0,0,-900

jump=CreateCube()
ScaleEntity jump,200,100,100
RotateEntity jump,15,0,0
PositionEntity jump,0,-70,-600
EntityType jump,ACTIVE

landing=CreateCube()
ScaleEntity landing,200,100,100
RotateEntity landing,15,180,0
PositionEntity landing,0,-70,-1000
EntityType landing,ACTIVE


grid_tex=CreateTexture( 256,256,1+4+8 )
SetBuffer TextureBuffer( grid_tex )
ScaleTexture grid_tex,500,500
Color 255,255,255:Rect 0,0,256,256,False
grid_tex2=CreateTexture( 32,32,1+8 )
SetBuffer TextureBuffer( grid_tex2 )
ScaleTexture grid_tex2,50,50
Color 0,0,255:Rect 0,0,32,32,False
SetBuffer BackBuffer()
flr=CreatePlane()
EntityType flr,ACTIVE
EntityTexture flr,grid_tex,0,1
EntityTexture flr,grid_tex2,0,0
TextureBlend grid_tex,3
EntityBlend flr,1
EntityAlpha flr,.6
EntityFX flr,1
PositionEntity flr,0,0,0


ScaleEntity car\v[1]\mesh,car\v[1]\radius,car\v[1]\radius/2,car\v[1]\radius
RotateEntity car\v[1]\mesh,0,0,90
PositionEntity car\v[1]\mesh,0,0,0

ScaleEntity car\v[2]\mesh,car\v[2]\radius,car\v[2]\radius/2,car\v[2]\radius
RotateEntity car\v[2]\mesh,0,0,90
PositionEntity car\v[2]\mesh,0,0,0

ScaleEntity car\v[5]\mesh,car\v[5]\radius,car\v[5]\radius/2,car\v[5]\radius
RotateEntity car\v[5]\mesh,0,0,90
PositionEntity car\v[5]\mesh,0,0,0

ScaleEntity car\v[6]\mesh,car\v[6]\radius,car\v[6]\radius/2,car\v[6]\radius
RotateEntity car\v[6]\mesh,0,0,90
PositionEntity car\v[6]\mesh,0,0,0

;********* functions defined ********************************************

; measure the start locations for each verlet so it can be fixed if it collapses
Function measure_pivots(name.Vobject, center_element)
	For count=1 To name\num_verlets
		If name\v[count]\part <> CENTER Then
			EntityParent name\v[count]\entity, name\v[center_element]\entity
			name\v[count]\start_loc\x=EntityX(name\v[count]\entity)
			name\v[count]\start_loc\y=EntityY(name\v[count]\entity)
			name\v[count]\start_loc\z=EntityZ(name\v[count]\entity)
			EntityParent name\v[count]\entity, 0
		Else
			name\v[count]\start_loc\x=0
			name\v[count]\start_loc\y=0
			name\v[count]\start_loc\z=0
		End If
	Next
End Function

; use this function to fix a collapsed Vobject
Function fix_verlet(name.Vobject)
	For count=1 To name\num_verlets
		EntityParent name\v[count]\entity, name\center\entity
		tempx# = name\v[count]\start_loc\x + name\center\current\x
		tempy# = name\v[count]\start_loc\y + name\center\current\y
		tempz# = name\v[count]\start_loc\z + name\center\current\z
		PositionEntity name\v[count]\entity, tempx, tempy, tempz
		name\v[count]\current\x = tempx
		name\v[count]\current\y = tempy
		name\v[count]\current\z = tempz
		name\v[count]\old\x = tempx
		name\v[count]\old\y = tempy
		name\v[count]\old\z = tempz
		EntityParent name\v[count]\entity, 0
	Next
End Function

Global crash
Function DoVerlet(name.Vobject, accelerator)
	For count = 0 To name\num_verlets
		If (name\v[count]\part = REAR_TIRE Or name\v[count]\part = FRONT_TIRE) And CountCollisions(name\v[count]\entity) >0
			TFormVector vgrav\x, vgrav\y,  vgrav\z, 0, name\player_pivot
			tempvax# = TFormedX()
			tempvay# = TFormedY()
			tempvaz# = TFormedZ()
			TFormVector name\v[count]\current\x, name\v[count]\current\y,  name\v[count]\current\z, 0, name\player_pivot
			temptempx#= TFormedX()
			temptempy#= TFormedY()
			temptempz#= TFormedZ()
			tempvmx# = TFormedX()
			tempvmy# = TFormedY()
			tempvmz# = TFormedZ()
			TFormVector name\v[count]\old\x, name\v[count]\old\y,  name\v[count]\old\z, 0, name\player_pivot
			tempvoldx# = TFormedX()
			tempvoldy# = TFormedY()
			tempvoldz# = TFormedZ()
			TFormVector EntityX(name\v[count]\entity,True), EntityY(name\v[count]\entity,True),  EntityZ(name\v[count]\entity,True), 0, name\player_pivot
			tempentityx# = TFormedX()
			tempentityy# = TFormedY()
			tempentityz# = TFormedZ()
			;tempvmx is purposefully not computed so the wheels only travel up and down, and forward/back
			tempvmy = tempvmy - (tempvoldy + (tempvay * (DeltaTime * DeltaTime))) + temptempy  
			tempvmz = tempvmz - (tempvoldz + (tempvaz * (DeltaTime * DeltaTime))) + temptempz
			tempvoldx = temptempx
			tempvoldy = temptempy
			tempvoldz = temptempz
			TFormVector tempvmx, tempvmy,  tempvmz, name\player_pivot, 0
			name\v[count]\current\x = TFormedX()
			name\v[count]\current\y = TFormedY()
			name\v[count]\current\z = TFormedZ()
			TFormVector tempvoldx, tempvoldy,  tempvoldz, name\player_pivot, 0
			name\v[count]\old\x = TFormedX()
			name\v[count]\old\y = TFormedY()
			name\v[count]\old\z = TFormedZ()
			Else
				name\v[count]\gravity\x = vgrav\x
				name\v[count]\gravity\y = vgrav\y
				name\v[count]\gravity\z = vgrav\z
				tempx# = name\v[count]\current\x
				tempy# = name\v[count]\current\y
				tempz# = name\v[count]\current\z
				name\v[count]\current\x = name\v[count]\current\x - (name\v[count]\old\x + (name\v[count]\gravity\x * (DeltaTime * DeltaTime))) + tempx
				name\v[count]\current\y = name\v[count]\current\y - (name\v[count]\old\y + (name\v[count]\gravity\y * (DeltaTime * DeltaTime))) + tempy
				name\v[count]\current\z = name\v[count]\current\z - (name\v[count]\old\z + (name\v[count]\gravity\z * (DeltaTime * DeltaTime))) + tempz
				name\v[count]\old\x = tempx
				name\v[count]\old\y = tempy
				name\v[count]\old\z = tempz
		End If
		If name\v[count]\part = REAR_TIRE  Or  name\v[count]\part = FRONT_TIRE  Or name\v[count]\part = BODY Then
			PositionEntity name\v[count]\entity, name\v[count]\current\x, name\v[count]\current\y, name\v[count]\current\z
			EntityParent  name\v[count]\entity, name\player_pivot
			name\acceleration = (-accelerator * name\horsepower * traction) / name\mass
			name\velocity = (name\velocity - (name\velocity * world_friction)) + (DeltaTime# * name\acceleration)
			name\distance =  DeltaTime# * DeltaTime# * name\acceleration * .5 * traction
			name\position=name\position + name\distance	
			MoveEntity name\player_pivot, 0, 0, name\distance
			EntityParent  name\v[count]\entity, 0
			If name\v[count]\part = FRONT_TIRE
				PositionEntity name\v[count]\entity, name\v[count]\current\x, name\v[count]\current\y, name\v[count]\current\z
				EntityParent  name\v[count]\entity, name\player_pivot
				TurnEntity name\player_pivot, 0, temp_turn, 0
				EntityParent  name\v[count]\entity, 0
			End If	
			Else 
				PositionEntity name\v[count]\entity, name\v[count]\current\x, name\v[count]\current\y, name\v[count]\current\z
		End If
	Next
	UpdateWorld
	
	crash=0
	For count = 0 To name\num_verlets
		If (name\v[count]\part = FRONT_TIRE Or REAR_TIRE) And Abs(Name\v[count]\current\y - EntityY(name\v[count]\Entity)) >9 Then crash=crash+1
	Next
	If crash >= 1 Then
		For count = 0 To name\num_verlets
			name\v[count]\current\y=name\v[count]\current\y + 5
			name\v[count]\old\y=name\v[count]\current\y
			PositionEntity name\v[count]\entity, name\v[count]\current\x, name\v[count]\current\y, name\v[count]\current\z
		Next
		UpdateWorld
	End If

	turn_rate = 0
	traction = 0
	For count = 0 To name\num_verlets
		If CountCollisions(name\v[count]\entity) And name\v[count]\part = FRONT_TIRE Then
			turn_rate = turn_rate + .7
			traction = traction + .25
		End If
		If CountCollisions(name\v[count]\entity) And name\v[count]\part = REAR_TIRE Then
			traction = traction + .25
		End If
		name\v[count]\current\x = EntityX(name\v[count]\entity)
		name\v[count]\current\y = EntityY(name\v[count]\entity)
		name\v[count]\current\z = EntityZ(name\v[count]\entity)
	Next
	For n = 1 To ITERATIONS
		For c.Constraint = Each Constraint
			setDistance(c\v1, c\v2, c\d)
			c\v1\old\x = c\v1\old\x + (c\v1\current\x - c\v1\old\x) * (c\v1\contact_friction * DeltaTime)
			c\v1\old\y = c\v1\old\y + (c\v1\current\y - c\v1\old\y) * (c\v1\contact_friction * DeltaTime)
			c\v1\old\z = c\v1\old\z + (c\v1\current\z - c\v1\old\z) * (c\v1\contact_friction * DeltaTime)

		Next
	Next
	;body and wheel stuff
	PositionEntity name\player_pivot, EntityX(name\center\entity), EntityY(name\center\entity), EntityZ(name\center\entity)
	name\X_vec = EntityX(name\x1\entity) - EntityX(name\x2\entity)
	name\Y_vec = EntityY(name\x1\entity) - EntityY(name\x2\entity)
	name\Z_vec = EntityZ(name\x1\entity) - EntityZ(name\x2\entity)
	AlignToVector name\player_pivot, name\X_vec, name\Y_vec, name\Z_vec, 1
	For count=0 To name\num_verlets
		If name\v[count]\part = FRONT_TIRE Or name\v[count]\part = REAR_TIRE Then
			AlignToVector name\v[count]\entity, name\X_vec, name\Y_vec, name\Z_vec, 1
		End If
	Next
	name\X_vec = EntityX(name\z1\entity) - EntityX(name\z2\entity)
	name\Y_vec = EntityY(name\z1\entity) - EntityY(name\z2\entity)
	name\Z_vec = EntityZ(name\z1\entity) - EntityZ(name\z2\entity)
	AlignToVector name\player_pivot, name\X_vec, name\Y_vec, name\Z_vec, 3
	For count=0 To name\num_verlets
		If name\v[count]\part = FRONT_TIRE Or name\v[count]\part = REAR_TIRE Then
			AlignToVector name\v[1]\entity, name\X_vec, name\Y_vec, name\Z_vec, 3
		End If
	Next
	;wheel spin isnt working right. blitz internal bug?
	TFormVector name\v[0]\current\x - name\v[0]\old\x, name\v[0]\current\y - name\v[0]\old\y,  name\v[0]\current\z - name\v[0]\old\z, name\v[0]\entity, name\player_pivot
	roll=roll+TFormedZ()
	;TurnEntity name\v[1]\entity, roll * radius, 0, 0, False
	TurnEntity name\v[1]\entity, TFormedZ() * name\v[1]\radius, 0, 0, False
	TurnEntity name\v[2]\entity, TFormedZ() * name\v[2]\radius, 0, 0, False
	TurnEntity name\v[5]\entity, TFormedZ() * name\v[5]\radius, 0, 0, False
	TurnEntity name\v[6]\entity, TFormedZ() * name\v[6]\radius, 0, 0, False
End Function

Function SetDistance(v1.VerletPack,v2.VerletPack,dist#)	
		vtemp1\x=v1\current\x - v2\current\x
		vtemp1\y=v1\current\y - v2\current\y
		vtemp1\z=v1\current\z - v2\current\z
		deltalength# = Sqr((vTemp1\x * vTemp1\x) + (vTemp1\y * vTemp1\y) + (vTemp1\z * vTemp1\z))
		If deltalength <= 0.0 deltalength = 0.0000001
		diff# = (deltalength - dist) / deltalength
		txmass# =  v1\mass\x + v2\mass\x
		tymass# =  v1\mass\y + v2\mass\y
		tzmass# =  v1\mass\z + v2\mass\z

		v1\current\x=v1\current\x - vtemp1\x * (diff * (v2\mass\x / txmass)); * (diff+1.2) 
		v1\current\y=v1\current\y - vtemp1\y * (diff * (v2\mass\y / tymass))  * (diff+1)
		v1\current\z=v1\current\z - vtemp1\z * (diff * (v2\mass\z / tzmass)); * (diff+1.2)
		v2\current\x=v2\current\x + vtemp1\x *(diff * (v1\mass\x / txmass)); / (diff+1.2)
		v2\current\y=v2\current\y + vtemp1\y *(diff * (v1\mass\y / tymass))  / (diff+1)
		v2\current\z=v2\current\z + vtemp1\z *(diff * (v1\mass\z / tzmass)); / (diff+1.2)
End Function

Function Verlet.VerletPack(x#,y#,z#,radius#, mass#, part,mesh,state,collision_type, contact_friction#)
	v.VerletPack = New VerletPack
	v\current = Vector(x,y,z)	;current location
	v\old = Vector(x,y,z)	;old location
	v\start_loc = Vector(0,0,0) ; initalize with zeros to be filled later
	v\part=part		;part identifier such as wheel or body
	If radius <= 0.0 radius = 0.01
	v\radius = radius	;collision radius
	If mass <= 0.0 mass = 0.01
	If v\part= FRONT_TIRE Or v\part= REAR_TIRE Then v\mass = Vector(100,mass,100) Else v\mass = Vector(400,400,400)
	;v\mass\y = mass		;point mass
	v\entity = CreatePivot()	;used as the collision element
	PositionEntity v\entity,x,y,z,True
	v\mesh=mesh		;mesh assigned if any
	If mesh<>0 Then EntityParent  v\mesh, v\entity,True
	v\state=state		;true for collideable, false for non collideable
	If v\state=True Then
		EntityType v\entity, collision_type
		EntityRadius v\entity,radius#
	End If
	v\contact_friction=contact_friction#
	v\gravity = Vector(0.0,0.0,0.0)
	Return v
End Function

Function Constraint2.Constraint(v1.VerletPack,v2.VerletPack)
	c.Constraint = New Constraint
	c\v1 = v1
	c\v2 = v2
	c\d = Sqr((v2\current\x - v1\current\x)^2 + (v2\current\y - v1\current\y)^2 + (v2\current\z - v1\current\z)^2)
	;Return c	; You may need this someday ... we don't for what we have here
End Function

;// Create a Vector
Function Vector.Vector(x#=0.0,y#=0.0,z#=0.0)
	v.Vector = New Vector
	v\x=x
	v\y=y
	v\z=z
	Return v
End Function 

;display directions
While Not KeyHit(57)
	RenderWorld
	Text 20,20, "Tab changes view from mouse look modes to front/side views."
	Text 20,35, "Arrow keys control vehicle.
	Text 20,50, "Escape exits program."
	Text 20,65, "Space bar resets vehicle"
	Text 20,80, "Hit space bar to begin."
	Flip False
Wend

;temp_Vobject2.Vobject = First Vobject
Global turn_rate#=0
DeltaTime#=.09
HidePointer
fRate = (1000/72) ;*set second number to desired frame rate
;**************** main loop ***************************************	
While Not KeyHit(1)
	time1 = MilliSecs() ;time at start of processing loop
	temp_turn#=0
	accelerator=0
	If KeyDown(203) temp_turn=turn_rate
	If KeyDown(205) temp_turn=-turn_rate
	If KeyDown(200) accelerator=1
	If KeyDown(208) accelerator=-1
	If KeyDown(57) Then 
		vGrav\y=0
		fix_verlet(car.Vobject) 
		Else 
			vGrav.Vector = Vector(0.0,9,0.0)
	End If
		DoVerlet(car.Vobject, accelerator)
	If KeyHit(15) Then 
		view=view+1
		If view >=3 Then view=0
	End If
	PositionEntity cam,EntityX(car\center\entity),EntityY(car\center\entity),EntityZ(car\center\entity)
	tempmousex#=tempmousex-MouseXSpeed()
	tempmousey#=tempmousey+MouseYSpeed()
	Select view
	Case 0 
		RotateEntity cam, tempmousey+10 , tempmousex+180, 0
	Case 1
		RotateEntity cam,tempmousey , EntityYaw(car\player_pivot,True)+90, 0
	Case 2
		RotateEntity cam,tempmousey , EntityYaw(car\player_pivot,True)+180, 0
	End Select
	MoveEntity cam,0,0,-90
	MoveMouse WIDTH/2,HEIGHT/2	
	RenderWorld
	Delay fRate - (MilliSecs() - time1) ;delay execution
	Flip False
Wend
End

This "demo" is more fun than half the full-featured Blitz programs I've seen. :) Pleasant memories of playing Rush 2049 float through my mind. Very very very cool.

thank you for the comment. but more importantly thank you doing the original port. if you hadnt done that i would still be banging my head against the wall.

cool. Nice to see a good example of verlet physics in games! Car dynamics is a little off, but o well. as you said "work in progress". suspension is nice. it gives you a good feel of speed, and turning.

This is a Cool Demo I look forward to seeing it finished off

Awesome! Looks like it could be used to make a simple game right now. Nice work.

Wow. As far as I'm concerned, that's near perfect for arcade-y racers!

Great !!

I hope the final code will be also available for the community .

Bolo Loco

Wow, that is great!! Lots o' fun. Kind of easy to roll.. must be an SUV!

I hope you don't mind me playing with the code a bit...

I had a model of a VolksWagen GTI (I think it's called the Lupo in Europe) that I had made for a friend many years back, just sitting on my HD. So I imported it to B3D and slapped it into your verlet car code. I also made a tiny stunt track. The models (B3D) and code (bb, not exe) are in a zip here:

http://www.almackey.com/verletvw.zip

Great little car model Al!!

DMC -> Good stuff. can't wait until the next version.

OMG i was laughing my ass off trying to get it up the ramps hahhaha. Al good show man. i wanted to add a car body and and a track etc but i dont have any webhosting. so this is great im glad you did it. for one thing it shows what promise this system has, but it also is a much more rigorous test of its current failings.

most of the vehicle instability stems from the set distance function and how collision is being handled. those two areas need tons of work. also the friction model needs finishing, the frame work is laid down for 3 types of friction: world friction (think air resistance), rolling friction, and contact friction (commonly refered to as static friction).

other refinements that need to be done are...
constraining the tire to only move up and down.
adding wheel turn left/right tied to steering.
making the turn rate dependant on vehicle speed.
adding braking, tire slipping and skidding.
finding a way to stop the car from rolling as easily (most likely tied to no wheel slipping).
adding more verlets to more accuratly surround the vehicle body.
improve the integrity of the structure so it doesnt collapse as easily.

it goes on and on.

if anybody gets a creative spurt take the code and run wild. i unfortunatly have little time right now =(

Very impressive!

I done this CRAZY stunt! :)

Remember that car jump in one of the bond movies, up the curvy twisty ramp in the red car with the cop in?

I hit the ramp with 2 wheels, done a 360 roll and landed perfect LOL!

This is fun, great work :)

Tom

Huh! This was FUN! How could have I missed this thread so totally... GREAT stuff! Car flipped over quite easily though and then slided a loooong time, sometimes spinning bit oddly... but all in all, very promising! This should be a good start for any car game... who needs Havok or Karma, when you can code something like this with Blitz? :)

This is indeed neat stuff.

Excelent stuff!

If you add some friction into it , it will get more realistic.

Update: although i cant post the code change now, i have almost solved the lateral roll over problem. the problem was in fact caused by near infinite static friction for the wheels. so to put it simply the car was like a train on tracks. no give at all between the tire and the road. by allowing a simple linear 50 percent slip the car now will skid a little when turning to tightly. but if you still push it to hard it will roll. so its not perfect but its a step in the right direction.

if anyone is actually following this thread, just want to let ya know that although i will post updates like this, most likely i wont post actuall code changes until they are significant enough to post.

next on the agenda is fix the per verlet friction code and re-enable wind resitance.

I'm definately interested in any and all updates. I've also added a few more things to do in my stunt course.. if you're interested I can post that.

Al im interested in what ya come up with for sure. maybe if i ever find the time to get this thing a little more stable you could web host the code with the car? i dont have any way to web host with my current provider.

but whatever ya come up with unfortunatly i dont have a lot of time to work on this so updates will be slow.

Me too!

dmc: I've just tried modifying your code to make the car a bit more stable, and one way is to move just the wheels out from the body, so the 'springs' are not vertical but diagonal. This instantly makes it much less likely to roll over. Also I lowered the body a bit (or raised the wheels dep. upon how you look at it) to make to car less top-heavy, and made the wheels slightly smaller.

It still doesn't slide about, so I'd like to see the mods you made to allow the wheels to slide, but at least it doesn't flip over so often.

One thing I found with my ODE car was to add a pendulum weight way below the car (effectively underground, with no collision and invisible). This made a huge difference to the stability of the car. Maybe you could try this also? (I've not had time to understand all your code yet).

Very good work though - nice and stable, even in high speed impacts.

If I remember correctly we/I used something like this in the 3Dmark2001 too, to get the truck "stabilized".

Im pleased to see some folks getting interested in this, and possibly spend some time to improve it???
If thats the case then I think i should spend some time explaining a few things.

First the code is a mess still. There are alot of half finished ideas all thru it. The one area that is
especially messed up is the friction code. Now lets start by reaching an agreement what types of friction
we need and why.

lets start with a contact friction type that is a variable assigned to each verlet. Each verlet
represents a "part" of the car. So contact friction on chassis or "body" parts need to be very high.
So When the car rolls over or land on the roof it will decelerate rapidly. Body verlet friction will
not change so its rather simple to implement. Now the verlet contact friction for the wheels is much more
complex. It needs to have at least two values. The first is rolling friction. This value is used whenever
the direction of travel matches the rolling direction of the wheel. when in this state the friction will
be very very low. But each time the car turns forces are applied away from the rolling direction. In this
case a static friction model needs to be used. The tire needs to stick to the road until a critical point
is reached where the forces away from the direction of roll exceed the ability of the tire to stick to the
road. Then once the forces have exceeded that critical point they need to let loose with a much lower level
of friction. As the car slows and the forces diminish then the tire will need to "re-stick" to the road.

the second major friction type is world friction. Think of this as air resistance. Now there is a peculiar
effect with air resistance where its resitance is a product of the vehicles speed. At zero velocity air
resistance is zero. but at much higher velocities it reaches such a high value that the vehicle will reach
a state known as terminal velocity. Terminal velocity simply means that the vehicle has reached its maximum
velocity.

So as a first step here is a very simple change that will change the simulation from "a train on tracks" to a
linear slip allowed for the tires. remember this is not accurate because we need two states for the wheels
and since this is simply linear it means the wheels are allowed to slip all the time.
In the DoVerlet function change this line;
;tempvmx is purposefully not computed so the wheels only travel up and down, and forward/back
TO;
tempvmx = tempvmx - ((tempvoldx*.5) + (tempvax * (DeltaTime * DeltaTime))) + (temptempx * .5)
you will need to reduce the turn_rate variable, also located in DoVerlet, because now that the wheels
are allowed to slip the force applied to turn the vehicle is applied with much less resistance. I suggest
changing it from;
turn_rate = turn_rate + .7
To
turn_rate = turn_rate + .5
Now this change allows 50 percent of the forces that previously we entirely excluded to now be computed.
Note the car will still roll over if you push it hard.

Remember how we needed two states for the tire? Well this is a simple hack to illustrate how we can achieve
the those states.
In the DoVerlet function change this line;
;tempvmx is purposefully not computed so the wheels only travel up and down, and forward/back

To this;
If Abs(tempvmx - tempvoldx) > 3 Then
tempvmx = tempvmx - ((tempvoldx*1) + (tempvax * (DeltaTime * DeltaTime))) + (temptempx * 1)
Else tempvmx = tempvmx - ((tempvoldx*.1) + (tempvax * (DeltaTime * DeltaTime))) + (temptempx * .1)
End If

And reduce the turn_rate, also located in DoVerlet, from;
turn_rate = turn_rate + .7
TO
turn_rate = turn_rate + .6 or even lower.

How this works is, it computes the difference from the old position to the new position. The difference is
effectively the force, or more accuratly the velocity change, exerted on the tire. when the difference is greater
than 3 the verlet is allowed to fully travel in all 3 axis with no friction. it wont look realistic but it will
prove that we can achieve two states.

Ok thats enough for now. Have fun.

vorderman, cool, glad your looking at it. in a way i want the car design to be unstable so i can find the problems with the math. then i can correct the math to improve stability and later on refine the verlet structure so it more closely matches a real vehicle. later on when the math is more complete there will be many many changes to the verlet placement including placing more of them to more accuratly form to the shape of the vehicle.

hmm never though of a pendulum effect. thats a very interesting concept, and one i think i will use if i cant solve the unstability problems with better formulas. thanks for that!!

ok heres a big update. lots of stuff fixed. read top of code for details.

;credit: miracle did the original port of verlet physics To BB. this code is based on that port.
;aug 27 03
;fixed per verlet friction contact friction
;added slip state to tires
;roll over in the ROLL axis problem much improved. still has problem with pitch roll over.
;moved z axis force from pivot to per verlet calculation
;cleaned up a bunch of junk code.
;changed chase cam to be more exciting - well ok its not exciting but it move more lol. it does however have a problem when car is upside down.
;fixed frozen front wheel.

Graphics3D HEIGHT,WIDTH,16,2
Const HEIGHT=640					; graphics width
Const WIDTH=480					; graphics height
Const ACTIVE=1					; collision type
Const VERLET=2					; collision Type
Const FRONT_TIRE=0				; Vobject part name
Const REAR_TIRE=1					; Vobject part name
Const BODY=2						; Vobject part name
Const CENTER=3					; Vobject part name
Const SIZE#=8					; just a multiplier for how big the Vobject will be
Const ITERATIONS = 2				; How many loops through the "relaxation" routine, Lower = speed up / lose accuracy
Global DeltaTime#					; Time between physics calculations
Global vGrav.Vector = Vector(0.0,9,0.0)	; Gravity. yes i know its a positive value. still dont know why this is but it works.
Global vTemp1.Vector = Vector(0,0,0)	; Some temporary vectors for calculations
Global vTemp2.Vector = Vector(0,0,0)
Global world_friction#=0				; air resistance
Global temp_turn#=0
front_stiff=20						; This is actually the mass value for the front wheel. lower mass = less stiff. caution will collapse
rear_stiff=30						; This is actually the mass value for the rear wheel. lower mass = less stiff. caution will collapse

Type Vector
	Field x#
	Field y#
	Field z#
End Type

Type VerletPack							
	Field start_loc.vector					; Defines where this verlet started at so we can fix it when it gets to far out of place
	Field current.Vector						; Current position
	Field old.Vector						; Last position
	Field gravity.Vector						; Accumulated forces
	Field radius#							; Collider radius
	Field mass.vector						; Point mass of this particular verlet
	Field entity							; Pivot assigned to this verlet for both position and collision
	Field mesh							; Mesh assigned to this verlet if any such as wheels or body parts
	Field part								; Describes what verlet represents. example wheel or body part.
	Field state							; Collideable status true/false	
	Field contact_friction#					; When in contact with the ground how much friction is applied
	Field traction							; true if tire is sticking, false if its skidding
End Type

Type Constraint							; Two verlets connected by a mutual spring
	Field v1.VerletPack						; First verlet
	Field v2.VerletPack						; Second verlet
	Field d#								; Distance between verlets
End Type

Type Vobject								; This is the parent object that the verlets are associated with
	Field v.VerletPack[8]					; The array of individual verlets
	Field num_verlets						; Total number of verlets (array dim value)
	Field player_pivot						; Pivot used to represent player. this pivot is dynamically controlled by player.
	Field player							; Mesh used to represent the player. this mesh is parented to player_pivot
	Field center.VerletPack					; Used to position player_pivot but not neccessarily parented to.
	Field x1.VerletPack						; x1 and x2 are used to define a vector left/right to align player_pivot
	Field x2.VerletPack
	Field z1.VerletPack						; z1 and z2 are used to define a vector forward/aft to align player_pivot
	Field z2.VerletPack
	Field X_vec#							; vectors for calculations
	Field Y_vec#
	Field Z_vec#
	Field mass#							; Mass for physics calculation on entire Vobject
	Field horsepower#						; Force for physics calculations on entire Vobject
	Field acceleration#						; Rate at which the Vobject accelerates
End Type

;***** make the vehicle ****************************************
	tempx# = 0							;start location of vehicle
	tempy# = 20							;start location of vehicle
	tempz# = 150							;start location of vehicle
	Global car.Vobject = New Vobject 			;initialize the Vobject type
	car\player_pivot=CreatePivot()			;this is the master pivot that the player will contol
	car\player=CreateCube(car\player_pivot)	;mesh that is assigned to player_pivot. in this case a simple cube for a car body
	ScaleEntity car\player, 15,6,30			;get car body into postion and scaled etc
	EntityColor car\player, 255,0,0
	PositionEntity car\player, 0, 2, -6
	car\num_verlets = 8						;total number of verlets in the Vobject. count from zero
	car\mass=10							;this mass value is used for physics calculations on player_pivot.
	car\horsepower = 500					;the force exerted on z axis,local to pivot, of verlet
	sx# = 1.9								;just a multiplier for the Vobject size
	sy# = 1.2								;just a multiplier for the Vobject size
	sz# = 2.65							;just a multiplier for the Vobject size
	
	;parameters   x,y,z,radius, mass, part,mesh,state,collision_type, contact_friction
	a.VerletPack = Verlet(tempx - SIZE * sx, tempy - SIZE * sy, tempz - SIZE * sz,  7, front_stiff, FRONT_TIRE, CreateCylinder(12), True, VERLET, .01)
	b.VerletPack = Verlet(tempx + SIZE * sx, tempy - SIZE * sy, tempz - SIZE * sz, 7, front_stiff, FRONT_TIRE, CreateCylinder(12), True, VERLET, .01)
	c.VerletPack = Verlet(tempx + SIZE * sx, tempy + SIZE * sy, tempz - SIZE * sz, 7, 400.0, BODY, 0, True, VERLET, .07)
	d.VerletPack = Verlet(tempx - SIZE * sx, tempy + SIZE * sy, tempz - SIZE * sz, 7, 400.0, BODY, 0, True, VERLET, .07)
	e.VerletPack = Verlet(tempx - SIZE * sx, tempy - SIZE * sy, tempz + SIZE * sz, 9, rear_stiff, REAR_TIRE, CreateCylinder(12), True, VERLET, .01)
	f.VerletPack = Verlet(tempx + SIZE * sx, tempy - SIZE * sy, tempz + SIZE * sz, 9, rear_stiff, REAR_TIRE, CreateCylinder(12), True, VERLET, .01)
	g.VerletPack = Verlet(tempx + SIZE * sx, tempy + SIZE * sy, tempz + SIZE * sz, 7, 400.0, BODY, 0, True, VERLET, .07)
	h.VerletPack = Verlet(tempx - SIZE * sx, tempy + SIZE * sy, tempz + SIZE * sz, 7, 400.0, BODY, 0, True, VERLET, .07)
	i.VerletPack = Verlet(tempx, tempy + 5, tempz + 8, 7, 400.0, CENTER, 0, False, VERLET, 0)
	
	; Edges
	Constraint2(a,b)
	Constraint2(b,c)
	Constraint2(a,d)
	Constraint2(c,d)
	Constraint2(e,f)	
	Constraint2(f,g)
	Constraint2(e,h)
	Constraint2(g,h)
	Constraint2(a,e)
	Constraint2(b,f)
	Constraint2(c,g)
	Constraint2(d,h)

	; Cross-faces
	Constraint2(a,c)
	Constraint2(b,d)
	Constraint2(e,g)
	Constraint2(f,h)
	Constraint2(a,f)
	Constraint2(a,h)
	Constraint2(b,e)
	Constraint2(b,g)
	Constraint2(c,f)
	Constraint2(c,h)
	Constraint2(d,e)
	Constraint2(d,g)

	; Diagonals
	Constraint2(a,g)
	Constraint2(b,h)
	Constraint2(c,e)
	Constraint2(d,f)
	
	; Constraining the center sphere
	Constraint2(a,i)
	Constraint2(b,i)
	Constraint2(c,i)
	Constraint2(d,i)
	Constraint2(e,i)
	Constraint2(f,i)
	Constraint2(g,i)
	Constraint2(h,i)

	; Assign individual verlets to the array	
	car\v[0] = i
	car\v[1] = a
	car\v[2] = b
	car\v[3] = c
	car\v[4] = d
	car\v[5] = e
	car\v[6] = f
	car\v[7] = g
	car\v[8] = h
	
	; assign a verlet the center position
	car\center=i
	; Set up variables used for player mesh/pivot aligntovector. one is left to right, other is forward back.
	car\x1=c
	car\x2=d
	car\z1=g
	car\z2=c
	
	PositionEntity car\player_pivot, EntityX(car\center\entity),EntityY(car\center\entity),EntityZ(car\center\entity)
	measure_pivots(car.Vobject, 0)
;****** end make vehicle *******************************************************************


Collisions VERLET,ACTIVE,2,2
MoveMouse WIDTH/2,HEIGHT/2

lgt = CreateLight()
LightColor lgt,300,300,300
RotateEntity lgt,35,0,0
AmbientLight 94,94,80
Global cam = CreateCamera()
CameraFogMode cam,0
CameraFogColor cam,128,128,180
CameraClsColor cam,128,128,180
CameraRange cam,1,4000
CameraFogRange cam,500,3000
CameraZoom cam,1.25

bump=CreateCylinder(4)
ScaleEntity bump, 5,600,20
RotateEntity bump,0,0,90
EntityType bump, ACTIVE
EntityColor bump,0,255,0
PositionEntity bump,0,0,-500
PositionEntity CopyEntity(bump),0,0,-600
PositionEntity CopyEntity(bump),0,0,-700
PositionEntity CopyEntity(bump),0,0,-800
PositionEntity CopyEntity(bump),0,0,-900

jump=CreateCube()
ScaleEntity jump,200,100,100
RotateEntity jump,15,0,0
PositionEntity jump,0,-70,-600
EntityType jump,ACTIVE

landing=CreateCube()
ScaleEntity landing,200,100,100
RotateEntity landing,15,180,0
PositionEntity landing,0,-70,-1000
EntityType landing,ACTIVE

grid_tex=CreateTexture( 256,256,1+4+8 )
SetBuffer TextureBuffer( grid_tex )
ScaleTexture grid_tex,500,500
Color 255,255,255:Rect 0,0,256,256,False
grid_tex2=CreateTexture( 32,32,1+8 )
SetBuffer TextureBuffer( grid_tex2 )
ScaleTexture grid_tex2,50,50
Color 0,0,255:Rect 0,0,32,32,False
SetBuffer BackBuffer()
flr=CreatePlane()
EntityType flr,ACTIVE
EntityTexture flr,grid_tex,0,1
EntityTexture flr,grid_tex2,0,0
TextureBlend grid_tex,3
EntityBlend flr,1
EntityAlpha flr,.6
EntityFX flr,1
PositionEntity flr,0,0,0

ScaleEntity car\v[1]\mesh,car\v[1]\radius,car\v[1]\radius/2,car\v[1]\radius
RotateEntity car\v[1]\mesh,0,0,90
PositionEntity car\v[1]\mesh,0,0,0

ScaleEntity car\v[2]\mesh,car\v[2]\radius,car\v[2]\radius/2,car\v[2]\radius
RotateEntity car\v[2]\mesh,0,0,90
PositionEntity car\v[2]\mesh,0,0,0

ScaleEntity car\v[5]\mesh,car\v[5]\radius,car\v[5]\radius/2,car\v[5]\radius
RotateEntity car\v[5]\mesh,0,0,90
PositionEntity car\v[5]\mesh,0,0,0

ScaleEntity car\v[6]\mesh,car\v[6]\radius,car\v[6]\radius/2,car\v[6]\radius
RotateEntity car\v[6]\mesh,0,0,90
PositionEntity car\v[6]\mesh,0,0,0

;********* functions defined ********************************************

; measure the start locations for each verlet so it can be fixed if it collapses
Function measure_pivots(name.Vobject, center_element)
	For count=1 To name\num_verlets
		If name\v[count]\part <> CENTER Then
			EntityParent name\v[count]\entity, name\v[center_element]\entity
			name\v[count]\start_loc\x=EntityX(name\v[count]\entity)
			name\v[count]\start_loc\y=EntityY(name\v[count]\entity)
			name\v[count]\start_loc\z=EntityZ(name\v[count]\entity)
			EntityParent name\v[count]\entity, 0
		Else
			name\v[count]\start_loc\x=0
			name\v[count]\start_loc\y=0
			name\v[count]\start_loc\z=0
		End If
	Next
End Function

; use this function to fix a collapsed Vobject
Function fix_verlet(name.Vobject)
	For count=1 To name\num_verlets
		EntityParent name\v[count]\entity, name\center\entity
		tempx# = name\v[count]\start_loc\x + name\center\current\x
		tempy# = name\v[count]\start_loc\y + name\center\current\y
		tempz# = name\v[count]\start_loc\z + name\center\current\z
		PositionEntity name\v[count]\entity, tempx, tempy, tempz
		name\v[count]\current\x = tempx
		name\v[count]\current\y = tempy
		name\v[count]\current\z = tempz
		name\v[count]\old\x = tempx
		name\v[count]\old\y = tempy
		name\v[count]\old\z = tempz
		EntityParent name\v[count]\entity, 0
	Next
End Function

Global crash, debugx#
Function DoVerlet(name.Vobject, accelerator)
	For count = 0 To name\num_verlets
		If (name\v[count]\part = REAR_TIRE Or name\v[count]\part = FRONT_TIRE) And CountCollisions(name\v[count]\entity) >0
			TFormVector vgrav\x, vgrav\y,  vgrav\z, 0, name\player_pivot
			tempvax# = TFormedX()
			tempvay# = TFormedY()
			tempvaz# = TFormedZ()
			TFormVector name\v[count]\current\x, name\v[count]\current\y,  name\v[count]\current\z, 0, name\player_pivot
			temptempx#= TFormedX()
			temptempy#= TFormedY()
			temptempz#= TFormedZ()
			tempvmx# = TFormedX()
			tempvmy# = TFormedY()
			tempvmz# = TFormedZ()
			TFormVector name\v[count]\old\x, name\v[count]\old\y,  name\v[count]\old\z, 0, name\player_pivot
			tempvoldx# = TFormedX()
			tempvoldy# = TFormedY()
			tempvoldz# = TFormedZ()
			TFormVector EntityX(name\v[count]\entity,True), EntityY(name\v[count]\entity,True),  EntityZ(name\v[count]\entity,True), 0, name\player_pivot
			tempentityx# = TFormedX()
			tempentityy# = TFormedY()
			tempentityz# = TFormedZ()
			debugx=tempvmx - tempvoldx
			If Abs(tempvmx - tempvoldx) > 3 Then
				name\v[count]\traction=False
				tempvmx = tempvmx - ((tempvoldx*.9) + (tempvax * (DeltaTime * DeltaTime))) + (temptempx * .9)
				tempvmy = tempvmy - ((tempvoldy * .9) + (tempvay * (DeltaTime * DeltaTime))) + (temptempy * .9)  
				tempvmz = tempvmz - ((tempvoldz * .9) + ((tempvaz + (accelerator * name\horsepower / name\mass)) * (DeltaTime * DeltaTime))) + (temptempz * .9)
				Else
				name\v[count]\traction=True 
				tempvmx = tempvmx - ((tempvoldx*.1) + (tempvax * (DeltaTime * DeltaTime))) + (temptempx * .1)
				tempvmy = tempvmy - ((tempvoldy * (1- name\v[count]\contact_friction)) + (tempvay * (DeltaTime * DeltaTime))) + (temptempy * (1- name\v[count]\contact_friction))  
				tempvmz = tempvmz - ((tempvoldz * (1- name\v[count]\contact_friction)) + ((tempvaz + (accelerator * name\horsepower / name\mass)) * (DeltaTime * DeltaTime))) + (temptempz * (1- name\v[count]\contact_friction))
			End If
			tempvoldx = temptempx
			tempvoldy = temptempy
			tempvoldz = temptempz
			TFormVector tempvmx, tempvmy,  tempvmz, name\player_pivot, 0
			name\v[count]\current\x = TFormedX()
			name\v[count]\current\y = TFormedY()
			name\v[count]\current\z = TFormedZ()
			TFormVector tempvoldx, tempvoldy,  tempvoldz, name\player_pivot, 0
			name\v[count]\old\x = TFormedX()
			name\v[count]\old\y = TFormedY()
			name\v[count]\old\z = TFormedZ()
			Else
				name\v[count]\gravity\x = vgrav\x
				name\v[count]\gravity\y = vgrav\y
				name\v[count]\gravity\z = vgrav\z
				tempx# = name\v[count]\current\x
				tempy# = name\v[count]\current\y
				tempz# = name\v[count]\current\z
				If CountCollisions(name\v[count]\entity) >0 Then
 					name\v[count]\current\x = name\v[count]\current\x - ((name\v[count]\old\x * (1- name\v[count]\contact_friction)) + (name\v[count]\gravity\x * (DeltaTime * DeltaTime))) + (tempx * (1- name\v[count]\contact_friction))
					name\v[count]\current\y = name\v[count]\current\y - ((name\v[count]\old\y * (1- name\v[count]\contact_friction)) + (name\v[count]\gravity\y * (DeltaTime * DeltaTime))) + (tempy * (1- name\v[count]\contact_friction))
					name\v[count]\current\z = name\v[count]\current\z - ((name\v[count]\old\z * (1- name\v[count]\contact_friction)) + (name\v[count]\gravity\z * (DeltaTime * DeltaTime))) + (tempz * (1- name\v[count]\contact_friction))
					Else
						name\v[count]\current\x = name\v[count]\current\x - (name\v[count]\old\x + (name\v[count]\gravity\x * (DeltaTime * DeltaTime))) + tempx
						name\v[count]\current\y = name\v[count]\current\y - (name\v[count]\old\y + (name\v[count]\gravity\y * (DeltaTime * DeltaTime))) + tempy
						name\v[count]\current\z = name\v[count]\current\z - (name\v[count]\old\z + (name\v[count]\gravity\z * (DeltaTime * DeltaTime))) + tempz
				End If	
				name\v[count]\old\x = tempx
				name\v[count]\old\y = tempy
				name\v[count]\old\z = tempz
		End If
		If name\v[count]\part = FRONT_TIRE Then ;*** steering
			PositionEntity name\v[count]\entity, name\v[count]\current\x, name\v[count]\current\y, name\v[count]\current\z
			EntityParent  name\v[count]\entity, name\player_pivot
			TurnEntity name\player_pivot, 0, temp_turn, 0
			EntityParent  name\v[count]\entity, 0
				
			Else 
				PositionEntity name\v[count]\entity, name\v[count]\current\x, name\v[count]\current\y, name\v[count]\current\z
		End If
	Next
	UpdateWorld
	
	crash=0
	For count = 0 To name\num_verlets
		If (name\v[count]\part = FRONT_TIRE Or REAR_TIRE) And Abs(Name\v[count]\current\y - EntityY(name\v[count]\Entity)) >9 Then crash=crash+1
	Next
	If crash >= 1 Then
		For count = 0 To name\num_verlets
			name\v[count]\current\y=name\v[count]\current\y + 5
			name\v[count]\old\y=name\v[count]\current\y
			PositionEntity name\v[count]\entity, name\v[count]\current\x, name\v[count]\current\y, name\v[count]\current\z
		Next
		UpdateWorld
	End If

	turn_rate = 0
	For count = 0 To name\num_verlets
		If CountCollisions(name\v[count]\entity) And name\v[count]\part = FRONT_TIRE And name\v[count]\traction=True Then
			turn_rate = turn_rate + .5
		End If
		name\v[count]\current\x = EntityX(name\v[count]\entity)
		name\v[count]\current\y = EntityY(name\v[count]\entity)
		name\v[count]\current\z = EntityZ(name\v[count]\entity)
	Next
	For n = 1 To ITERATIONS
		For c.Constraint = Each Constraint
			setDistance(c\v1, c\v2, c\d)
		Next
	Next
	;body and wheel stuff
	PositionEntity name\player_pivot, EntityX(name\center\entity), EntityY(name\center\entity), EntityZ(name\center\entity)
	name\X_vec = EntityX(name\x1\entity) - EntityX(name\x2\entity)
	name\Y_vec = EntityY(name\x1\entity) - EntityY(name\x2\entity)
	name\Z_vec = EntityZ(name\x1\entity) - EntityZ(name\x2\entity)
	AlignToVector name\player_pivot, name\X_vec, name\Y_vec, name\Z_vec, 1
	For count=0 To name\num_verlets
		If name\v[count]\part = FRONT_TIRE Or name\v[count]\part = REAR_TIRE Then
			AlignToVector name\v[count]\entity, name\X_vec, name\Y_vec, name\Z_vec, 1
		End If
	Next
	name\X_vec = EntityX(name\z1\entity) - EntityX(name\z2\entity)
	name\Y_vec = EntityY(name\z1\entity) - EntityY(name\z2\entity)
	name\Z_vec = EntityZ(name\z1\entity) - EntityZ(name\z2\entity)
	AlignToVector name\player_pivot, name\X_vec, name\Y_vec, name\Z_vec, 3
	TFormVector name\v[0]\current\x - name\v[0]\old\x, name\v[0]\current\y - name\v[0]\old\y,  name\v[0]\current\z - name\v[0]\old\z, name\v[0]\entity, name\player_pivot
	TurnEntity name\v[1]\entity, TFormedZ() * name\v[1]\radius, 0, 0, False
	TurnEntity name\v[2]\entity, TFormedZ() * name\v[2]\radius, 0, 0, False
	TurnEntity name\v[5]\entity, TFormedZ() * name\v[5]\radius, 0, 0, False
	TurnEntity name\v[6]\entity, TFormedZ() * name\v[6]\radius, 0, 0, False
End Function

Function SetDistance(v1.VerletPack,v2.VerletPack,dist#)	
		vtemp1\x=v1\current\x - v2\current\x
		vtemp1\y=v1\current\y - v2\current\y
		vtemp1\z=v1\current\z - v2\current\z
		deltalength# = Sqr((vTemp1\x * vTemp1\x) + (vTemp1\y * vTemp1\y) + (vTemp1\z * vTemp1\z))
		If deltalength <= 0.0 deltalength = 0.0000001
		diff# = (deltalength - dist) / deltalength
		txmass# =  v1\mass\x + v2\mass\x
		tymass# =  v1\mass\y + v2\mass\y
		tzmass# =  v1\mass\z + v2\mass\z

		v1\current\x=v1\current\x - vtemp1\x * (diff * (v2\mass\x / txmass)); * (diff+1.2) 
		v1\current\y=v1\current\y - vtemp1\y * (diff * (v2\mass\y / tymass))  * (diff+1)
		v1\current\z=v1\current\z - vtemp1\z * (diff * (v2\mass\z / tzmass)); * (diff+1.2)
		v2\current\x=v2\current\x + vtemp1\x *(diff * (v1\mass\x / txmass)); / (diff+1.2)
		v2\current\y=v2\current\y + vtemp1\y *(diff * (v1\mass\y / tymass))  / (diff+1)
		v2\current\z=v2\current\z + vtemp1\z *(diff * (v1\mass\z / tzmass)); / (diff+1.2)
End Function

Function Verlet.VerletPack(x#,y#,z#,radius#, mass#, part,mesh,state,collision_type, contact_friction#)
	v.VerletPack = New VerletPack
	v\current = Vector(x,y,z)	;current location
	v\old = Vector(x,y,z)	;old location
	v\start_loc = Vector(0,0,0) ; initalize with zeros to be filled later
	v\part=part		;part identifier such as wheel or body
	If radius <= 0.0 radius = 0.01
	v\radius = radius	;collision radius
	If mass <= 0.0 mass = 0.01
	If v\part= FRONT_TIRE Or v\part= REAR_TIRE Then v\mass = Vector(100,mass,100) Else v\mass = Vector(400,400,400)
	v\entity = CreatePivot()	;used as the collision element
	PositionEntity v\entity,x,y,z,True
	v\mesh=mesh		;mesh assigned if any
	If mesh<>0 Then EntityParent  v\mesh, v\entity,True
	v\state=state		;true for collideable, false for non collideable
	If v\state=True Then
		EntityType v\entity, collision_type
		EntityRadius v\entity,radius#
	End If
	v\contact_friction=contact_friction#
	v\gravity = Vector(0.0,0.0,0.0)
	Return v
End Function

Function Constraint2.Constraint(v1.VerletPack,v2.VerletPack)
	c.Constraint = New Constraint
	c\v1 = v1
	c\v2 = v2
	c\d = Sqr((v2\current\x - v1\current\x)^2 + (v2\current\y - v1\current\y)^2 + (v2\current\z - v1\current\z)^2)
	;Return c	; You may need this someday ... we don't for what we have here
End Function

;// Create a Vector
Function Vector.Vector(x#=0.0,y#=0.0,z#=0.0)
	v.Vector = New Vector
	v\x=x
	v\y=y
	v\z=z
	Return v
End Function 

;display directions
While Not KeyHit(57)
	RenderWorld
	Text 20,20, "Tab changes view from mouse look modes to front/side views."
	Text 20,35, "Arrow keys control vehicle.
	Text 20,50, "Escape exits program."
	Text 20,65, "Space bar resets vehicle"
	Text 20,80, "Hit space bar to begin."
	Flip False
Wend

;temp_Vobject2.Vobject = First Vobject
Global turn_rate#=0
DeltaTime#=.09
HidePointer
fRate = (1000/72) ;*set second number to desired frame rate
view=2
;**************** main loop ***************************************	
While Not KeyHit(1)
	time1 = MilliSecs() ;time at start of processing loop
	temp_turn#=0
	accelerator=0
	If KeyDown(203) temp_turn=turn_rate
	If KeyDown(205) temp_turn=-turn_rate
	If KeyDown(200) accelerator=1
	If KeyDown(208) accelerator=-1
	If KeyDown(57) Then 
		vGrav\y=0
		fix_verlet(car.Vobject) 
		Else 
			vGrav.Vector = Vector(0.0,9,0.0)
	End If
		DoVerlet(car.Vobject, accelerator)
	If KeyHit(15) Then 
		view=view+1
		If view >=3 Then view=0
	End If
	PositionEntity cam,EntityX(car\center\entity),EntityY(car\center\entity),EntityZ(car\center\entity)
	tempmousex#=tempmousex-MouseXSpeed()
	tempmousey#=tempmousey+MouseYSpeed()
	Select view
	Case 0 
		RotateEntity cam, tempmousey+10 , tempmousex+180, 0
	Case 1
		RotateEntity cam,tempmousey , EntityYaw(car\player_pivot,True)+90, 0
	Case 2
		RotateEntity cam,EntityPitch(car\player_pivot,True)/4 +15 , EntityYaw(car\player_pivot,True)+180, EntityRoll(car\player_pivot,True) /2
	End Select
	MoveEntity cam,0,0,-150
	MoveMouse WIDTH/2,HEIGHT/2
	
	RenderWorld
	Text 20,20, "lateral velocity: "+debugx
	Delay fRate - (MilliSecs() - time1) ;delay execution
	Flip False
Wend
End

Hmm, mine's went in a bit of a different direction, with a few textures, a new track, and my own chase cam.

http://www.almackey.com/verletvw2.zip

DMC, I can host files for you if you want, but keep in mind that they'll be hosted on my account on a friend's server sitting on a friend of a friend's bandwith pipe. In other words, I can't personally guarantee it'll always be up.

thanks for the offer al, but i dont know when ill have time to make a "prettier version". the only thing im concerned with right now is getting the math/functionality as correct/stable as possible. but maybe you could add your stuff to the new code. and keep your chase cam its pretty cool.

the updated code seems to handle a little bit better so im pleased with that.

personally i wish i had time to make a game out of this. but since i dont, i making it available so those that do can make there own racing game or whatever they want =)

I've been working on moving my B3Ds into your new code.. it's working well, but there's still a bug I notice in both the new and old versions of the code. The front right tire doesn't spin! It's mostly an asthetic thing, I guess, but it would be nice if it did... (and I can't make heads or tails of most of the physics stuff so I'm having a hard time tracking it down myself)

hint:
You have one error in your code that makes the verlet structure unstabile.

In your setdistance function, where you calculate the springs...

diff# = (deltalength - dist) / deltalength
you should multiply the diff by 0.5

Because when you add vtemp*diff to other end of the spring and substract from the other end it makes the spring lenght wrong again, instead of correcting it.

to prove it:

x1=100:x2=150:dist=100
xs = x2-x1 = 50
deltalenght = sqr(xs*xs) = 50
diff# = (deltalength - dist) / deltalength = -1

x1 + xs*diff (50*-1)
x2 - xs*diff (50*-1)

-------> x1 = 100-50 : x2 = 150+50 , so now the distance is 150 and it should be 100.

Hmm. bouncer, it appears that that is correct. I'm using the same method as dmc for my distance corrections, but I can't check it now cause I'll have to close the browser, since it slows down the computer.

Anyway, the new version is much better. corrects many of my previous gripes. as far as myself, I've been progressing my system pretty well. I have psionic's ninja model do a backflip and suddenly merge into verlet physics-continuing the motion in a physichal way. Still super messy though. my collisions have run into a simple mathamatical barrier that will make it so I can't have double sided flat quads. I can do single sided just fine, but oh well. I'm lazy.I'll do it tommorow.

Hmm, that new version is much more stable.

However, it still seems that you end up with a car that will suddenly swap ends with no warning. This is exactly what I got with my ODE tests - because there is no simulation of the way rubber tyres mould to the road then the wheel is either touching the floor and gripping, or else it bounces slightly and all traction is lost.

I think that until a suitable tyre-dynamic is added that regulates the available grip/friction then creating a car model that can slide realistically and be controlled will be very difficult or impossible.

I really hope someone can prove me wrong though.

dmc, this is really fantastic stuff. I've even started to understand how it works -- at first glance the code looks very complicated, but reading through it, it turns out to be fairly straightforward to follow, so I'm looking forward to experimenting more with this.

Still, there's tons I wouldn't have a clue how to implement (all that wheel friction, etc), so please keep updating it -- I've waited ages for someone to implement decent car physics in Blitz, so big thanks from me for all your hard work!

I'm with James. I knew when I converted this verlet stuff it had a lot of potential --
nice to see that potential being realized.

Maybe someone is able to decipher the Pacejka tyre model that games like Racer use, as this seems to be a good way to model tyre forces and dynamics, and seems to be the missing piece in this (and the ODE) car physics systems.

I'm afraid it's a bit above me :(

This is brilliant

I went up the loop-type thing so fast the wheels ended up on the roof :)

BTW Miracle -- those thanks go to you too!

Will it be possible to do capsule to polygon collision with your system? Or better still polygon to polygon collision?

cya,
Mike

Vorderman, let me know what you think of this.....
i have a hunch that the quick flip in direction is being caused primarily by the mode switch code, from sticking to slipping, that is simply a binary decision. the verlets have lots of potential energy that is instantly released. what im trying to wrap my brain around is a way to allow the tire to start to slip gradually, and release enough energy before the car flips. all of this needs to happen over a small number of frames.

for a little proof of this concept, when i had the wheels using a constant 50 percent slip it never "flipped around".

the other contributing cause is the simple hack im using for steering. eventually i need to have a speed dependant steering method that will only allow for tight turns when velocity is slow and widen the allowable turn radius when velocity is very very high.

bouncer, ill take a look at what ya said when i get more.

necky, i dont have the foggiest idea of how to code collision systems. but assuming somebody did know how, heres a way to get polygon to polygon fast...
in the older post i started about verlet physics that code uses the verlet coordinates as vertex coords to make a real time deformable collision mesh. so with that you have a low poly mesh to check against.

Al, the one tire that doesnt spin hes been that way forever. i swear its a bug internal to blitz. someday it will be fixed.

I found it, I found it!! There's a bit of code that looks like this:

	For count=0 To name\num_verlets
		If name\v[count]\part = FRONT_TIRE Or name\v[count]\part = REAR_TIRE Then
			AlignToVector name\v[1]\entity, name\X_vec, name\Y_vec, name\Z_vec, 3
		End If
	Next

I'm not sure what it's supposed to be doing, but that AlignToVector is being performed on v[1] -- that front wheel -- and keeping it from spinning. Comment this out and it does spin, and the car seems to drive the same.

Thanks Al!!!!!!!
you da man.

most recent code post is now corrected.

Excellent work guys, I can play with this stuff for ages.

Also I don't know if it's of any help or if you already know about this site but it has some good info that might be of use.

http://www.miata.net/sport/Physics/

My latest:
http://www.almackey.com/verletvw3.zip

I got sick of the tiny window, so it relies on some calls to User32 (decls file included) to get the desktop res. An EXE is included if you don't want to install my decls file (if you do, it goes in Blitz3D/userlibs). There's three of my own camera modes here, including a drivers-eye view.

Al Mackey, the latest version is cool :)

I have not had this much fun since stunt car racer on the Atari ST :)

Yeah, that gets the wheel spinning, but it *looks* like that line should read:

AlignToVector name\v[count]\entity, name\X_vec, name\Y_vec, name\Z_vec, 3

(Note 'count' in place of '1']

... however, this stops all wheels spinning! The AlignToVector is different (ends in ,3 -- z-axis alignment) so must have some purpose, even if there's no visible difference after a few quick tests...?

BTW Al that new demo rocks! Only problem is the frame-limit code doesn't seem to work here. Although it runs reasonably on my laptop (fairly slow for 3D stuff), it runs unplayably fast on my brother's Athlon 1800/Geforce 4 machine... other than that, this has to be one of the coolest Blitz demos out there!

Awesome!! Al's new graphics/level really makes it cool. although the potential already showed threw the original.

Sorry bouncer, but I believe that your fix is incorrect. Easy mistake to make, and hard to test. I had to do a cube with 1 iteration to distinctly show incorectness with the multiply by .5 thing. The reason it's incorrect, is that it is factored in under you nose. The verlet masses are usually =1, so you end up with a tmass# of 2. then v1mass#/tmass#=.5, which is then multiplied by the diff#. I noticed that dmc is now using different mass values on different axis. interesting. Probably specific to the car sim. I was just going to save dmc from wasting time on figuring this out. but still a good point bouncer. took a little while for me to work out the fact that it's false.

Fantastic stuff! Easily the best car simulation ever done in Blitz! Mark you should hire dmc to do a native Blitz physics library ;)

Fredborg

i am homing in the on the problem where the cars rear end whips around after traction is lost. although the original does give us two states it just allows way to much potential energy to build up and when traction is lost the rear accelerates forward just like a rubber band. so heres what i got cookin.

speed dependant steering - as car goes faster the radius you can turn gets wider and wider. want to turn sharply slow down first.

for the tire traction code im adding a slip threshold and max value so i can fine tune exactly when the tires break loose and by how much. it is also specific to front or rear tires. my hope is i can get the rear to start to break early and cause a slower spin out rather than a snap.

bot builder i agree nothing is wrong with the way the distances are calculated. i didnt prove it out. just used the... "if it aint broke dont fix it theory" =) and since i wasnt having much problem with the structure being unstable i wasnt about to change it.

sometime soon i have to get terminal velocity working because that dang car just keeps going faster and faster and faster.....

ohh the reason im using different masses for each axis is i can control how much energy is transfered from one verlet to the other by changing the masses. so for the wheels, they have very low masses. the body has much higher mass. this makes for a squishy suspension.

now where was i.... oh yeah bleeding off potential energy hmmmm.

have fun

hmmm. I'm interested in your method of minimizing number of verlets used by using individual verlets as wheels.
Definitly minimizes work, and probably allows you to do everything much faster. I might consider adding
that to my own wishlist for my engine. In a little while, once my demo is cleaned up and I get my own
webspace to post stuff, I'll put it up.

Oh yeah, and I forgot to mention in my previous post that the ninja constraints were completely computer applied for comple ragdoll affect, which is a bad thing, as all the ninja's apendages could go throu himself, creating a very mishapen humanish lump on the ground. I have actually figured out a reasonably good method of algorithmically assigning joint limits. Simply rotate each joint in all angles until the mesh intersects its parent. then assign a constraint that only occurs at a minimum distance, the amount between the parents parent, and the current entity.

with my newest idea(of a long and extravagant series), and making sure the .5 thing was incorrect, I never got arround to the collision thing, which is looking to be fairly more difficult than I thought.

PS:if you do make a blitz-native physics system, please put updates and demos in the forums. I'd like to help as well, but I can't code much in anything but blitz.

AlignToVector name\v[ count or "1" in orignial code ]\entity, name\X_vec, name\Y_vec, name\Z_vec, 3

Replace "count" or "1" there with a 3 and it works right.

OMFG..

This is total class m8. Iv just spent the better part of an hour just reading through the code.

Its awsome .. I hope you dont mine me using it. cos its outstanding.. well done and good work..

bot builder: You are right!... just corrected the bug in my own engine as well ;)
If you didn't have weights then it would be correct, but the way point weights are calculated removes the need for multiplying by 0.5

To prevent tires from "springing" onto the top of the vehicle, you might try attaching each tire
to every verlet in the car body. Yeah, I know, that's a big mess o' constraints, but I think it'll
stop the tire pushing through to the top and then sticking there.

miracle since i need a loose suspension im guessing that no matter how many constraints are involved that eventually a case will come up where impact force is greater than the spring tension.

my solution is to detect when the verlets have been moved to far and to back track in time until they are within acceptable range and then globally to the verlet system bleed off excess energy.

i already have a crude method in the code above that is working for most circumstances. it just needs to be refined. one of the many things on my to-do list.

that code is basically what allows the car to go off a jump and not "bounce" uncontrollably.

last bit: for you folks still looking at that frozen tire code error. just remove it. it was a fragment accidently left in from a different idea now abandoned.

In my 2D rigidbody engine I use a kind of autospringing routine which assignes spring from every point to every other point in the object... I know that's alot of spring , but it's the only way to keep complex structures from collapsing.

The car in your example works pretty fine, because it's symmetric ... something less symmetric would collapse right away with small number of springs.

Hmmm. Actually, in theory, each verlet should only need to connect to four others. Of course, the key is the selection of the four others. If you could do iterations until all constraints were satisfied, this would work perfectly. yet of course, being realtime engines, it would collapse on itself as soon as one constraint messed up. so if you add maybe 6 or 7 or 8 well selected constraints for each verlet, it should work.

Maybe once I get my collisions, I'll make a constraint evolver that might be ported to your system. It would be rather simple. have it evolve arrays, where each element was either 1 or zero(might optimize it to do binary). Each element represents whether a constraint between two verlets exists. Create 100 of these randomly assigned objects with different constraints, and see how well each maintains it's relationships. Here's the fitness factor I think i'll use:

fitness=constraints*coef#/amountwrong#

then take the top 10, replicate and mutate 5 times each, and then add 50 more randoms.

eventually, it should converge on a good constraint setup that you can put into a file in binary.

[EDIT: I forgot to mention that you should check my post on the code wizrds forum of blitzcoder. I posted an example of my physics system as well as a link to psionics ninja model.]

Yes, in the ideal case not much springs is needed... but to calculate which ones are needed for structure stability is hard. Your method might work though.

Your link on blitzcoder isn't working btw.

Guys,

Ihave to tell you - you are gods!

I have been amazed in the last two weeks how this thread has developed, and now you have a terrific demo.

I just wish I could understand some of the underlying code so I could get to grips with it myself!

Great stuff - keep it up!

IPete2.

much improved control. you must use als graphics

;credit: miracle did the original port of verlet physics To BB. this code is based on that port.

;aug 27 03

;fixed per verlet friction contact friction

;added slip state to tires

;roll over in the ROLL axis problem much improved. still has problem with pitch roll over.

;moved z axis force from pivot to per verlet calculation

;cleaned up a bunch of junk code.

;changed chase cam to be more exciting - well ok its not exciting but it move more lol. it does however have a problem when car is upside down.


	Graphics3D (WIDTH,HEIGHT,0,2)

Const WIDTH=640

Const HEIGHT=480

Const ACTIVE=1					; collision type

Const VERLET=2					; collision Type

Const FRONT_TIRE=0				; Vobject part name

Const REAR_TIRE=1					; Vobject part name

Const BODY=2						; Vobject part name

Const CENTER=3					; Vobject part name

Const SIZE#=8					; just a multiplier for how big the Vobject will be

Global DeltaTime#					; Time between physics calculations

Global vGrav.Vector = Vector(0.0,9,0.0)	; Gravity. yes i know its a positive value. still dont know why this is but it works.

Global vTemp1.Vector = Vector(0,0,0)	; Some temporary vectors for calculations

Global vTemp2.Vector = Vector(0,0,0)

Global world_friction#=0				; air resistance

Global temp_turn#=0

Global turn_allowed#=0

front_stiff=20						; This is actually the mass value for the front wheel. lower mass = less stiff. caution will collapse
rear_stiff=40						; This is actually the mass value for the rear wheel. lower mass = less stiff. caution will collapse

Type Dust
	Field Sprite				; The entity
	Field VelX#, VelY#, VelZ#	; Momentum
	Field Alpha#				; Transparency
	Field FadeRate#				; Rate at which transparency decays
	Field Size#, VelR#, SprRot#, Growth#, Friction#
End Type
Global DustSprite = LoadSprite("dust.png", 3)
SpriteViewMode(DustSprite, 3)
EntityBlend(DustSprite, 1)
HideEntity(DustSprite)


Type Vector

	Field x#

	Field y#

	Field z#

End Type



Type VerletPack							

	Field start_loc.vector					; Defines where this verlet started at so we can fix it when it gets to far out of place

	Field current.Vector						; Current position

	Field old.Vector						; Last position

	Field gravity.Vector						; Accumulated forces

	Field radius#							; Collider radius

	Field mass.vector						; Point mass of this particular verlet

	Field entity							; Pivot assigned to this verlet for both position and collision

	Field mesh							; Mesh assigned to this verlet if any such as wheels or body parts

	Field part								; Describes what verlet represents. example wheel or body part.

	Field state							; Collideable status true/false	

	Field contact_friction#					; When in contact with the ground how much friction is applied

	Field traction							; true if tire is sticking, false if its skidding
	
	Field wheel_slip#[2]					; slip accumulator. needed to "smooth" out the slip value

End Type



Type Constraint							; Two verlets connected by a mutual spring

	Field v1.VerletPack						; First verlet

	Field v2.VerletPack						; Second verlet

	Field d#								; Distance between verlets

End Type



Type Vobject								; This is the parent object that the verlets are associated with

	Field v.VerletPack[8]					; The array of individual verlets

	Field num_verlets						; Total number of verlets (array dim value)

	Field player_pivot						; Pivot used to represent player. this pivot is dynamically controlled by player.

	Field player							; Mesh used to represent the player. this mesh is parented to player_pivot

	Field center.VerletPack					; Used to position player_pivot but not neccessarily parented to.

	Field x1.VerletPack						; x1 and x2 are used to define a vector left/right to align player_pivot

	Field x2.VerletPack

	Field z1.VerletPack						; z1 and z2 are used to define a vector forward/aft to align player_pivot

	Field z2.VerletPack

	Field X_vec#							; vectors for calculations

	Field Y_vec#

	Field Z_vec#

	Field mass#							; Mass for physics calculation on entire Vobject

	Field horsepower#						; Force for physics calculations on entire Vobject

	Field acceleration#						; Rate at which the Vobject accelerates
	
	Field velocity#							; a place to store how fast Vobject is going in the z direction(forward back)

End Type



;***** make the vehicle ****************************************

	tempx# = 0							;start location of vehicle

	tempy# = 20							;start location of vehicle

	tempz# = 150							;start location of vehicle

	Global car.Vobject = New Vobject 			;initialize the Vobject type

	car\player_pivot=CreatePivot()			;this is the master pivot that the player will contol

	car\player = LoadMesh("carbody.B3D", car\player_pivot)
	Global CarInterior = LoadMesh("carinterior.B3D", car\player)
	ScaleEntity(car\player, 2, 2, 2)

	PositionEntity car\player, 0, 2, -6

	car\num_verlets = 8						;total number of verlets in the Vobject. count from zero

	car\mass=10							;this mass value is used for physics calculations on player_pivot.

	car\horsepower = 500					;the force exerted on z axis,local to pivot, of verlet
	
	sx# = 1.9								;just a multiplier for the Vobject size

	sy# = 1.2								;just a multiplier for the Vobject size

	sz# = 2.65							;just a multiplier for the Vobject size

	
	;parameters   x,y,z,radius, massX, massY, massZ, part,mesh,state,collision_type, contact_friction

	FrontTireSize# = 5 ; originally 7
	RearTireSize# = 5 ; originally 9

	tm = LoadMesh("tire.B3D", tire)
	verleta.VerletPack = Verlet(tempx - SIZE * sx, tempy - SIZE * sy, tempz - SIZE * sz,  FrontTireSize, 100, front_stiff, 100, FRONT_TIRE, tm, True, VERLET, .01)
	tm = LoadMesh("tire.B3D", tire)
	RotateMesh(tm, 180, 0, 0)
	verletb.VerletPack = Verlet(tempx + SIZE * sx, tempy - SIZE * sy, tempz - SIZE * sz, FrontTireSize, 100, front_stiff, 100, FRONT_TIRE, tm, True, VERLET, .01)

	verletc.VerletPack = Verlet(tempx + SIZE * sx, tempy + SIZE * sy, tempz - SIZE * sz, 7, 400, 400, 400.0, BODY, 0, True, VERLET, .07)

	verletd.VerletPack = Verlet(tempx - SIZE * sx, tempy + SIZE * sy, tempz - SIZE * sz, 7, 400, 400 ,400.0, BODY, 0, True, VERLET, .07)

	tm = LoadMesh("tire.B3D", tire)
	verlete.VerletPack = Verlet(tempx - SIZE * sx, tempy - SIZE * sy, tempz + SIZE * sz, RearTireSize, 100, rear_stiff, 100, REAR_TIRE, tm, True, VERLET, .01)

	tm = LoadMesh("tire.B3D", tire)
	RotateMesh(tm, 180, 0, 0)
	verletf.VerletPack = Verlet(tempx + SIZE * sx, tempy - SIZE * sy, tempz + SIZE * sz, RearTireSize, 100, rear_stiff, 100, REAR_TIRE, tm, True, VERLET, .01)

	verletg.VerletPack = Verlet(tempx + SIZE * sx, tempy + SIZE * sy, tempz + SIZE * sz, 7, 400, 400.0, 400, BODY, 0, True, VERLET, .07)

	verleth.VerletPack = Verlet(tempx - SIZE * sx, tempy + SIZE * sy, tempz + SIZE * sz, 7, 400, 400.0, 400, BODY, 0, True, VERLET, .07)

	verleti.VerletPack = Verlet(tempx, tempy + 5, tempz + 8, 7, 400, 400.0, 400, CENTER, 0, False, VERLET, 0)

	; Edges

	Constraint2(verleta,verletb)

	Constraint2(verletb,verletc)

	Constraint2(verleta,verletd)

	Constraint2(verletc,verletd)

	Constraint2(verlete,verletf)	

	Constraint2(verletf,verletg)

	Constraint2(verlete,verleth)

	Constraint2(verletg,verleth)

	Constraint2(verleta,verlete)

	Constraint2(verletb,verletf)

	Constraint2(verletc,verletg)

	Constraint2(verletd,verleth)



	; Cross-faces

	Constraint2(verleta,verletc)

	Constraint2(verletb,verletd)

	Constraint2(verlete,verletg)

	Constraint2(verletf,verleth)

	Constraint2(verleta,verletf)

	Constraint2(verleta,verleth)

	Constraint2(verletb,verlete)

	Constraint2(verletb,verletg)

	Constraint2(verletc,verletf)

	Constraint2(verletc,verleth)

	Constraint2(verletd,verlete)

	Constraint2(verletd,verletg)



	; Diagonals

	Constraint2(verleta,verletg)

	Constraint2(verletb,verleth)

	Constraint2(verletc,verlete)

	Constraint2(verletd,verletf)

	
	; Constraining the center sphere

	Constraint2(verleta,verleti)

	Constraint2(verletb,verleti)

	Constraint2(verletc,verleti)

	Constraint2(verletd,verleti)

	Constraint2(verlete,verleti)

	Constraint2(verletf,verleti)

	Constraint2(verletg,verleti)

	Constraint2(verleth,verleti)



	; Assign individual verlets to the array	

	car\v[0] = verleti

	car\v[1] = verleta

	car\v[2] = verletb

	car\v[3] = verletc

	car\v[4] = verletd

	car\v[5] = verlete

	car\v[6] = verletf

	car\v[7] = verletg

	car\v[8] = verleth

	
	; assign a verlet the center position

	car\center=verleti

	; Set up variables used for player mesh/pivot aligntovector. one is left to right, other is forward back.

	car\x1=verletc

	car\x2=verletd

	car\z1=verletg

	car\z2=verletc

	
	PositionEntity car\player_pivot, EntityX(car\center\entity),EntityY(car\center\entity),EntityZ(car\center\entity)

	measure_pivots(car.Vobject, 0)

;****** end make vehicle *******************************************************************





Collisions VERLET,ACTIVE,2,2


SunLight = CreateLight()
RotateEntity (SunLight, 50, 180+40, 0)
LightColor (SunLight, 224, 221, 203)
BakLight = CreateLight()
RotateEntity (BakLight, 20, 40, 0)
LightColor (BakLight, 94, 104, 103)
AmbientLight (64, 59, 48)

Global BkgObjs = CreatePivot()

flare = LoadSprite("flare.png")
EntityParent(flare, BkgObjs)
RotateEntity(flare, 50, 180+40, 0)
MoveEntity (flare, 0, 0, -8000)
ScaleSprite(flare, 5000, 5000)
EntityColor(flare, 255-128, 255-176, 255-235)
SpriteViewMode(flare, 3)

Global Sky = LoadMesh("sky.B3D")
ScaleEntity(Sky, 3.8*9500, 5.6*9500, 3.8*9500)
EntityFX(Sky, 1)

Global cam1 = CreatePivot(car\player)
PositionEntity (cam1, 2.8, 0.4, -1.8)
RotateEntity (cam1, 0, 180, 0)

Global cam2 = CreatePivot()

Global Camera = CreateCamera(cam2)
CameraZoom(Camera, 1.5)
CameraClsColor Camera,128,176,235
CameraRange Camera,0.5,10000
PositionEntity (Camera, 0, 10, 0)
camnul = CreatePivot()
camtarget = CreatePivot()

RearViewCam = CreateCamera(car\player)
PositionEntity (RearViewCam, 0.5, 0.5, 10)
TurnEntity (RearViewCam, 0, 0, 0)
CameraZoom(RearViewCam, 0.7)
CameraClsColor RearViewCam,128,176,235
CameraRange RearViewCam,0.5,10000
CameraViewport (RearViewCam, 0.55*ScrWidth, 0.05*ScrHeight, 0.4*ScrWidth, 0.15 * ScrHeight)
HideEntity(RearViewCam)

RearViewBlock = CreateCube(Camera)
vratio# = 1.0 * ScrHeight / ScrWidth
EntityColor(RearViewBlock, 0, 0, 0)
PositionEntity(RearViewBlock, 7.65, 11.5 * vratio, 10.7)
ScaleEntity(RearViewBlock, 6.3, 2.5 * vratio, 0.00001)
EntityOrder(RearViewBlock, -1)
HideEntity(RearViewBlock)

track = LoadMesh("track.B3D")
ScaleEntity (track, 70, 70, 70)
EntityType (track, ACTIVE)


ground_tex = LoadTexture("mud.png")
ScaleTexture ground_tex,500,500
Global flr=CreatePlane()
EntityType flr,ACTIVE
EntityTexture flr,ground_tex
EntityFX flr,1
PositionEntity flr,0,0,0



ScaleEntity car\v[1]\mesh,car\v[1]\radius,car\v[1]\radius/2,car\v[1]\radius

RotateEntity car\v[1]\mesh,0,0,90

PositionEntity car\v[1]\mesh,0,0,0



ScaleEntity car\v[2]\mesh,car\v[2]\radius,car\v[2]\radius/2,car\v[2]\radius

RotateEntity car\v[2]\mesh,0,0,90

PositionEntity car\v[2]\mesh,0,0,0



ScaleEntity car\v[5]\mesh,car\v[5]\radius,car\v[5]\radius/2,car\v[5]\radius

RotateEntity car\v[5]\mesh,0,0,90

PositionEntity car\v[5]\mesh,0,0,0



ScaleEntity car\v[6]\mesh,car\v[6]\radius,car\v[6]\radius/2,car\v[6]\radius

RotateEntity car\v[6]\mesh,0,0,90

PositionEntity car\v[6]\mesh,0,0,0



;********* functions defined ********************************************



; measure the start locations for each verlet so it can be fixed if it collapses

Function measure_pivots(name.Vobject, center_element)

	For count=1 To name\num_verlets

		If name\v[count]\part <> CENTER Then

			EntityParent name\v[count]\entity, name\v[center_element]\entity

			name\v[count]\start_loc\x=EntityX(name\v[count]\entity)

			name\v[count]\start_loc\y=EntityY(name\v[count]\entity)

			name\v[count]\start_loc\z=EntityZ(name\v[count]\entity)

			EntityParent name\v[count]\entity, 0

		Else

			name\v[count]\start_loc\x=0

			name\v[count]\start_loc\y=0

			name\v[count]\start_loc\z=0

		End If

	Next

End Function



; use this function to fix a collapsed Vobject

Function fix_verlet(name.Vobject)

	For count=1 To name\num_verlets

		EntityParent name\v[count]\entity, name\center\entity

		tempx# = name\v[count]\start_loc\x + name\center\current\x

		tempy# = name\v[count]\start_loc\y + name\center\current\y

		tempz# = name\v[count]\start_loc\z + name\center\current\z

		PositionEntity name\v[count]\entity, tempx, tempy, tempz

		name\v[count]\current\x = tempx

		name\v[count]\current\y = tempy

		name\v[count]\current\z = tempz

		name\v[count]\old\x = tempx

		name\v[count]\old\y = tempy

		name\v[count]\old\z = tempz

		EntityParent name\v[count]\entity, 0

	Next

End Function

Function wheel_force#(name.VObject, count, threshold#, max#)
	
	TFormPoint EntityX(name\v[count]\entity,True), EntityY(name\v[count]\entity,True), EntityZ(name\v[count]\entity,True), 0,  name\player_pivot
	
	tempx# = TFormedX()
	
	tempy# = TFormedY()
	
	tempz# = TFormedZ()
	
	force# = Abs(name\v[count]\start_loc\x - tempx) - threshold
	
	debugx=Abs(name\v[count]\start_loc\x - tempx)
	
	If force < 0 Then force=0
	
	temp#=Abs(threshold - max)
	
	name\v[count]\wheel_slip[0]=( (force / Sqr(force * force + temp * temp)) + name\v[count]\wheel_slip[1] + name\v[count]\wheel_slip[2])/3
	
	name\v[count]\wheel_slip[2]=name\v[count]\wheel_slip[1]
	
	name\v[count]\wheel_slip[1]=name\v[count]\wheel_slip[0]
	
	Return Sqr(name\v[count]\wheel_slip[0])

End Function


Global crash, debugx#, debugx2#, debugx3#

Function DoVerlet(name.Vobject, accelerator#)

	For count = 0 To name\num_verlets
		If name\v[count]\part = CENTER Then
			TFormVector name\v[count]\current\x, name\v[count]\current\y,  name\v[count]\current\z, 0, name\player_pivot
			temptempx#= TFormedX()
			temptempy#= TFormedY()
			temptempz#= TFormedZ()
 			TFormVector name\v[count]\old\x, name\v[count]\old\y,  name\v[count]\old\z, 0, name\player_pivot
			tempvoldx# = TFormedX()
			tempvoldy# = TFormedY()
			tempvoldz# = TFormedZ()
			If Abs(temptempz - tempvoldz) <.01 Then name\velocity=0 Else name\velocity =Abs(temptempz - tempvoldz)
		End If

		If (name\v[count]\part = REAR_TIRE Or name\v[count]\part = FRONT_TIRE) And CountCollisions(name\v[count]\entity) >0

			OnGround = 0
			For n = 1 To CountCollisions(name\v[count]\entity)
				If (CollisionEntity(name\v[count]\entity, n) = flr) OnGround = 1
			Next
			If (OnGround)
				chance# = Abs(accelerator) * 0.4
				If (Rnd(0,1) < chance)
					d.Dust = New Dust
					d\Sprite = CopyEntity(DustSprite)
					d\SprRot = Rnd(0,360)
					e = name\v[count]\entity
					PositionEntity(d\Sprite, EntityX(e,1), EntityY(e,1), EntityZ(e,1))
					d\VelX = Rnd(-1, 1)
					d\VelY = Rnd(0.3, 0.7)
					d\VelZ = Rnd(-1, 1)
					d\Alpha = 1
					d\FadeRate = Rnd(0.01, 0.05)
					d\Size = 6
					d\Growth = Rnd(0.6, 2)
					d\VelR = Rnd(-2, 2)
					d\Friction = 0
				End If
			End If

			TFormVector vgrav\x, vgrav\y,  vgrav\z, 0, name\player_pivot
			tempvax# = TFormedX()
			tempvay# = TFormedY()
			tempvaz# = TFormedZ()
			TFormVector name\v[count]\current\x, name\v[count]\current\y,  name\v[count]\current\z, 0, name\player_pivot
			temptempx#= TFormedX()
			temptempy#= TFormedY()
			temptempz#= TFormedZ()
			tempvmx# = TFormedX()
			tempvmy# = TFormedY()
			tempvmz# = TFormedZ()
			TFormVector name\v[count]\old\x, name\v[count]\old\y,  name\v[count]\old\z, 0, name\player_pivot
			tempvoldx# = TFormedX()
			tempvoldy# = TFormedY()
			tempvoldz# = TFormedZ()
			TFormVector EntityX(name\v[count]\entity,True), EntityY(name\v[count]\entity,True),  EntityZ(name\v[count]\entity,True), 0, name\player_pivot
			tempentityx# = TFormedX()
			tempentityy# = TFormedY()
			tempentityz# = TFormedZ()
			name\v[count]\traction=True
			If name\v[count]\part = REAR_TIRE Then
				temp_slip#= wheel_force(name.vobject, count,1.5,1.9)
				debugX2=temp_slip#
				tempvmx = tempvmx - ((tempvoldx * temp_slip) + (tempvax * (DeltaTime * DeltaTime))) + (temptempx * temp_slip)
				Else
					temp_slip#= wheel_force(name.vobject, count,.9,1.2)
					debugX3=temp_slip#
					tempvmx = tempvmx - ((tempvoldx * temp_slip) + (tempvax * (DeltaTime * DeltaTime))) + (temptempx * temp_slip)
			End If
			tempvmy = tempvmy - ((tempvoldy * (1- name\v[count]\contact_friction)) + (tempvay * (DeltaTime * DeltaTime))) + (temptempy * (1- name\v[count]\contact_friction))  
			tempvmz = tempvmz - ((tempvoldz * (1- name\v[count]\contact_friction)) + ((tempvaz + (accelerator * name\horsepower / name\mass)) * (DeltaTime * DeltaTime))) + (temptempz * (1- name\v[count]\contact_friction))
			
			tempvoldx = temptempx
			tempvoldy = temptempy
			tempvoldz = temptempz
			TFormVector tempvmx, tempvmy,  tempvmz, name\player_pivot, 0
			name\v[count]\current\x = TFormedX()
			name\v[count]\current\y = TFormedY()
			name\v[count]\current\z = TFormedZ()
			TFormVector tempvoldx, tempvoldy,  tempvoldz, name\player_pivot, 0
			name\v[count]\old\x = TFormedX()
			name\v[count]\old\y = TFormedY()
			name\v[count]\old\z = TFormedZ()
			Else
				name\v[count]\gravity\x = vgrav\x
				name\v[count]\gravity\y = vgrav\y
				name\v[count]\gravity\z = vgrav\z
				tempx# = name\v[count]\current\x
				tempy# = name\v[count]\current\y
				tempz# = name\v[count]\current\z
				If CountCollisions(name\v[count]\entity) >0 Then
 					name\v[count]\current\x = name\v[count]\current\x - ((name\v[count]\old\x * (1- name\v[count]\contact_friction)) + (name\v[count]\gravity\x * (DeltaTime * DeltaTime))) + (tempx * (1- name\v[count]\contact_friction))
					name\v[count]\current\y = name\v[count]\current\y - ((name\v[count]\old\y * (1- name\v[count]\contact_friction)) + (name\v[count]\gravity\y * (DeltaTime * DeltaTime))) + (tempy * (1- name\v[count]\contact_friction))
					name\v[count]\current\z = name\v[count]\current\z - ((name\v[count]\old\z * (1- name\v[count]\contact_friction)) + (name\v[count]\gravity\z * (DeltaTime * DeltaTime))) + (tempz * (1- name\v[count]\contact_friction))
					Else
						name\v[count]\current\x = name\v[count]\current\x - (name\v[count]\old\x + (name\v[count]\gravity\x * (DeltaTime * DeltaTime))) + tempx
						name\v[count]\current\y = name\v[count]\current\y - (name\v[count]\old\y + (name\v[count]\gravity\y * (DeltaTime * DeltaTime))) + tempy
						name\v[count]\current\z = name\v[count]\current\z - (name\v[count]\old\z + (name\v[count]\gravity\z * (DeltaTime * DeltaTime))) + tempz
				End If	
				name\v[count]\old\x = tempx
				name\v[count]\old\y = tempy
				name\v[count]\old\z = tempz
		End If
		If name\v[count]\part = FRONT_TIRE Then ;*** steering
			PositionEntity name\v[count]\entity, name\v[count]\current\x, name\v[count]\current\y, name\v[count]\current\z
			EntityParent  name\v[count]\entity, name\player_pivot
			TurnEntity name\player_pivot, 0, temp_turn, 0
			EntityParent  name\v[count]\entity, 0
				
			Else 
				PositionEntity name\v[count]\entity, name\v[count]\current\x, name\v[count]\current\y, name\v[count]\current\z
		End If
	Next
	UpdateWorld
	
	crash=0
	For count = 0 To name\num_verlets
		If (name\v[count]\part = FRONT_TIRE Or REAR_TIRE) And Abs(Name\v[count]\current\y - EntityY(name\v[count]\Entity)) >9 Then crash=crash+1
	Next
	If crash >= 1 Then
		For count = 0 To name\num_verlets
			name\v[count]\current\y=name\v[count]\current\y + 5
			name\v[count]\old\y=name\v[count]\current\y
			PositionEntity name\v[count]\entity, name\v[count]\current\x, name\v[count]\current\y, name\v[count]\current\z
		Next
		UpdateWorld
	End If

	turn_allowed# = 0
	For count = 0 To name\num_verlets
		If CountCollisions(name\v[count]\entity) And name\v[count]\part = FRONT_TIRE And name\v[count]\traction=True Then
			turn_allowed = turn_allowed + .7
			If turn_allowed > 1 Then turn_allowed=1
		End If
		name\v[count]\current\x = EntityX(name\v[count]\entity)
		name\v[count]\current\y = EntityY(name\v[count]\entity)
		name\v[count]\current\z = EntityZ(name\v[count]\entity)
	Next
	;For n = 1 To ITERATIONS
		For c.Constraint = Each Constraint
			setDistance(c\v1, c\v2, c\d)
			setDistance(c\v2, c\v1, c\d)
		Next
	;Next
	;body and wheel stuff
	PositionEntity name\player_pivot, EntityX(name\center\entity), EntityY(name\center\entity), EntityZ(name\center\entity)
	name\X_vec = EntityX(name\x1\entity) - EntityX(name\x2\entity)
	name\Y_vec = EntityY(name\x1\entity) - EntityY(name\x2\entity)
	name\Z_vec = EntityZ(name\x1\entity) - EntityZ(name\x2\entity)
	AlignToVector name\player_pivot, name\X_vec, name\Y_vec, name\Z_vec, 1
	For count=0 To name\num_verlets
		If name\v[count]\part = FRONT_TIRE Or name\v[count]\part = REAR_TIRE Then
			AlignToVector name\v[count]\entity, name\X_vec, name\Y_vec, name\Z_vec, 1
		End If
	Next
	name\X_vec = EntityX(name\z1\entity) - EntityX(name\z2\entity)
	name\Y_vec = EntityY(name\z1\entity) - EntityY(name\z2\entity)
	name\Z_vec = EntityZ(name\z1\entity) - EntityZ(name\z2\entity)
	AlignToVector name\player_pivot, name\X_vec, name\Y_vec, name\Z_vec, 3
	
	TFormVector name\v[0]\current\x - name\v[0]\old\x, name\v[0]\current\y - name\v[0]\old\y,  name\v[0]\current\z - name\v[0]\old\z, name\v[0]\entity, name\player_pivot
	TurnEntity name\v[1]\entity, TFormedZ() * name\v[1]\radius, 0, 0, False 
	TurnEntity name\v[2]\entity, TFormedZ() * name\v[2]\radius, 0, 0, False
	TurnEntity name\v[5]\entity, TFormedZ() * name\v[5]\radius, 0, 0, False
	TurnEntity name\v[6]\entity, TFormedZ() * name\v[6]\radius, 0, 0, False
End Function



Function SetDistance(v1.VerletPack,v2.VerletPack,dist#)	

		vtemp1\x=v1\current\x - v2\current\x

		vtemp1\y=v1\current\y - v2\current\y

		vtemp1\z=v1\current\z - v2\current\z

		deltalength# = Sqr((vTemp1\x * vTemp1\x) + (vTemp1\y * vTemp1\y) + (vTemp1\z * vTemp1\z))

		If deltalength <= 0.0 deltalength = 0.0000001

		diff# = (deltalength - dist) / deltalength

		txmass# =  v1\mass\x + v2\mass\x

		tymass# =  v1\mass\y + v2\mass\y

		tzmass# =  v1\mass\z + v2\mass\z

		v1\current\x=v1\current\x - vtemp1\x * (diff * (v2\mass\x / txmass)); * (diff+1.2) 

		v1\current\y=v1\current\y - vtemp1\y * (diff * (v2\mass\y / tymass))  * (diff+1)

		v1\current\z=v1\current\z - vtemp1\z * (diff * (v2\mass\z / tzmass)); * (diff+1.2)

		v2\current\x=v2\current\x + vtemp1\x *(diff * (v1\mass\x / txmass)); / (diff+1.2)

		v2\current\y=v2\current\y + vtemp1\y *(diff * (v1\mass\y / tymass))  / (diff+1)

		v2\current\z=v2\current\z + vtemp1\z *(diff * (v1\mass\z / tzmass)); / (diff+1.2)

End Function

Function Verlet.VerletPack(x#,y#,z#,radius#, massX#, massY#, massZ#, part,mesh,state,collision_type, contact_friction#)
	
	v.VerletPack = New VerletPack
	
	v\current = Vector(x,y,z)	;current location
	
	v\old = Vector(x,y,z)	;old location
	
	v\start_loc = Vector(0,0,0) ; initalize with zeros to be filled later
	
	v\mass = Vector(0,0,0) ;initialize mass
	
	v\part=part		;part identifier such as wheel or body
	
	If radius <= 0.0 radius = 0.01
	
	v\radius = radius	;collision radius
	
	v\mass\x=massX
	
	v\mass\y=massY
	
	v\mass\z=massZ
	
	v\entity = CreatePivot()	;used as the collision element
	
	PositionEntity v\entity,x,y,z,True
	
	v\mesh=mesh		;mesh assigned if any
	
	If mesh<>0 Then EntityParent  v\mesh, v\entity,True
	
	v\state=state		;true for collideable, false for non collideable
	
	If v\state=True Then
	
		EntityType v\entity, collision_type
	
		EntityRadius v\entity,radius#
	
	End If
	
	v\contact_friction=contact_friction#
	
	v\gravity = Vector(0.0,0.0,0.0)
	
	Return v

End Function

Function Constraint2.Constraint(v1.VerletPack,v2.VerletPack)

	c.Constraint = New Constraint

	c\v1 = v1

	c\v2 = v2

	c\d = Sqr((v2\current\x - v1\current\x)^2 + (v2\current\y - v1\current\y)^2 + (v2\current\z - v1\current\z)^2)

	;Return c	; You may need this someday ... we don't for what we have here

End Function



;// Create a Vector

Function Vector.Vector(x#=0.0,y#=0.0,z#=0.0)

	v.Vector = New Vector

	v\x=x

	v\y=y

	v\z=z

	Return v

End Function 



;display directions

While Not KeyHit(57)

	RenderWorld

	Text 20,20, "Tab changes view."

	Text 20,35, "Arrow keys control vehicle.

	Text 20,50, "Escape exits program."

	Text 20,65, "Space bar resets vehicle"

	Text 20,80, "Hit space bar to begin."

	Flip False

Wend



;temp_Vobject2.Vobject = First Vobject

Global turn_rate#=0

DeltaTime#=.09

HidePointer

fRate = (1000/72) ;*set second number to desired frame rate

view=0

;**************** main loop ***************************************	

PrevCP# = 0
PrevCY# = 0
PrevCR# = 0
CamHeight# = 20 ; camera height above player
CamDist# = 150 ; camera dist from player
CamLag# = 0.5 ; Tightness of camera to its target (1 = strongest)
Global accelerator#=0
While Not KeyHit(1)

	time1 = MilliSecs() ;time at start of processing loop

	maxturn=2.0	
	If KeyDown(203) Then
		temp_turn=(temp_turn + .1) / ((car\velocity/100)+1) * turn_allowed
		;If temp_turn >maxturn Then temp_turn = maxturn
		If Abs(temp_turn) >maxturn Then temp_turn = maxturn * Sgn(temp_turn)
		Else If KeyDown(205) Then
			temp_turn=(temp_turn - .1) / ((car\velocity/100)+1) * turn_allowed
			If temp_turn < -maxturn Then temp_turn = -maxturn
			Else
				;temp_turn=temp_turn/1.03
				temp_turn = -(MouseXSpeed()/1) * turn_allowed
				If Abs(temp_turn) >maxturn Then temp_turn = maxturn * Sgn(temp_turn)
				If temp_turn > -.01 And temp_turn < .01 Then temp_turn=0		
	End If
		
	If car\velocity <2.5 Then temp_turn=temp_turn * Sqr(Sqr(car\velocity * 2.5) /2.5)
	
	If KeyDown(200) Then
		accelerator=accelerator + .01
		If accelerator >1 Then accelerator = 1
		Else If KeyDown(208) Then
			accelerator=accelerator - .01
			If accelerator < -1 Then accelerator = -1
			Else
				accelerator=accelerator/1.03
				If accelerator > -.01 And accelerator < .01 Then accelerator=0		
	End If

	If KeyDown(57) Then 

		vGrav\y=0

		fix_verlet(car.Vobject) 

		Else 

			vGrav.Vector = Vector(0.0,9,0.0)

	End If

		DoVerlet(car.Vobject, accelerator)

	If KeyHit(15) Then 

		view=view+1

		If view >=3 Then view=0
		
		If (view = 0) Or (view = 2) ; Chase
			CameraZoom(Camera, 1.5)
			EntityParent(Camera, Cam2)
			RotateEntity(Camera, 0, 0, 0)
			HideEntity(RearViewCam)
			EntityOrder(CarInterior, 0)
			HideEntity(RearViewBlock)
			If (view = 0)
				CamHeight# = 20 ; camera height above player
				CamDist# = 150 ; camera dist from player
				CamLag# = 0.5 ; Tightness of camera to its target (1 = strongest)
			Else
				CamHeight# = 30 ; camera height above player
				CamDist# = 70 ; camera dist from player
				CamLag# = 0.02 ; Tightness of camera to its target (1 = strongest)
				CamLag# = 0.01 ; Tightness of camera to its target (1 = strongest)
			End If
		Else If (view = 1) ; Internal
			CameraZoom(Camera, 0.7)
			EntityParent(Camera, Cam1)
			RotateEntity(Camera, 0, 180, 0)
			ShowEntity(RearViewCam)
			EntityOrder(CarInterior, -1)
			ShowEntity(RearViewBlock)
		End If

		PositionEntity(Camera, 0, 0, 0)
	End If

	; Move dust
	For dst.Dust = Each Dust
		dst\Alpha = dst\Alpha - dst\FadeRate
		dst\Size = dst\Size + dst\Growth
		If (dst\Alpha <= 0) Or (dst\Size <= 0)
			FreeEntity(dst\Sprite)
			Delete(dst)
		Else
			; Particles grow over time
			dsize# = dst\Size * 0.5
			ScaleSprite (dst\Sprite, dsize, dsize)

			; Fade particles over time
			alpha# = dst\Alpha
			If (alpha > 1) alpha = 1
			
			; Fade particles close to camera
			dist# = EntityDistance(dst\Sprite, Camera)
			If (dist < dsize) And (dist > 0) alpha = alpha * (dsize/dist)
			EntityAlpha(dst\Sprite, alpha)

			; Rotate particles over time
			dst\SprRot = dst\SprRot + dst\VelR
			RotateSprite (dst\Sprite, dst\SprRot)

			If (dst\Friction > 0)
				fr# = 1-(dst\Friction)
				dst\VelX = dst\VelX * fr
				dst\VelY = dst\VelY * fr
				dst\VelZ = dst\VelZ * fr
			End If

		EndIf
	Next

	; My chase cam
	te = car\player_pivot
	cyaw# = VectorYaw(EntityX(te,1) - EntityX(cam2), CamHeight + EntityY(te,1) - EntityY(cam2), EntityZ(te,1) - EntityZ(cam2))
	cpit# = VectorPitch(EntityX(te,1) - EntityX(cam2), CamHeight + EntityY(te,1) - EntityY(cam2), EntityZ(te,1) - EntityZ(cam2))
	maxpitch# = 70
	If (cpit > maxpitch) cpit = maxpitch
	If (cpit < -maxpitch) cpit = -maxpitch
	PositionEntity(camnul, EntityX(te,1), EntityY(te,1), EntityZ(te,1))
	RotateEntity(camnul, cpit, cyaw, 0)
	MoveEntity(camnul, 0, 0, -CamDist)
	camy# = EntityY(camnul,1) + CamHeight
	If (camy < 5) camy = 5
	PositionEntity (CamTarget, EntityX(camnul,1), camy, EntityZ(camnul,1))
	TranslateEntity(cam2, (EntityX(CamTarget)-EntityX(Cam2))*CamLag, (EntityY(CamTarget)-EntityY(Cam2))*CamLag, (EntityZ(CamTarget)-EntityZ(Cam2))*CamLag)
	TurnEntity (cam2, DeltaPitch(cam2, te) * 0.5, DeltaYaw(cam2, te) * 0.5, -EntityRoll(cam2) * 0.05)

	; My interior cam
	thisCP# = CloseAngle(EntityPitch(car\player, 1), prevCP)
	thisCY# = CloseAngle(EntityYaw(car\player, 1), prevCY)
	thisCR# = CloseAngle(EntityRoll(car\player, 1), prevCR)
	
	fr# = 0.3 ; camera friction
	afr# = 1.0 - fr

	RotateEntity (cam1, (thisCP*fr)+(prevCP*afr), (thisCY*fr)+(prevCY*afr), (thisCR*fr)+(prevCR*afr), 1)

	prevCP# = EntityPitch(cam1, 1)
	prevCY# = EntityYaw(cam1, 1)
	prevCR# = EntityRoll(cam1, 1)

	PositionEntity(BkgObjs, EntityX(Camera, 1), EntityY(Camera, 1), EntityZ(Camera, 1))
	PositionEntity(Sky, EntityX(Camera, 1), 0, EntityZ(Camera, 1))

	RenderWorld
	
	Text 20,20, "Lateral velocity: "+debugx
	Text 20,35, "Rear slip: "+debugx2
	Text 20,50, "Front slip: "+debugx3
	Text 20,65, "Velocity: "+car\velocity
	MoveMouse WIDTH/2,HEIGHT/2
	Delay fRate - (MilliSecs() - time1) ;delay execution

	Flip False

Wend

End


Function CloseAngle(source#, target#)
	While (source < target - 180)
		source = source + 360
	Wend
	While (source > target + 180)
		source = source - 360
	Wend
	Return source
End Function