Code archives/3D Graphics - Maths/Avoid_entity function

This code has been declared by its author to be Public Domain code.

Download source code

Avoid_entity function by Nate the Great
(Posted 18 years ago)
This is another version of the yaw to entity code that allows for avoiding as well as attraction!

The cone goes to the white box and avoids the red box. I haven't found any glitches in the avoid_entity function yet. Please tell me if you do. 
; The number of logic updates per second.
Const C_LOGIC_FREQUENCY = 50

; The interval (in milliseconds) between logic updates.
Const C_LOGIC_INTERVAL# = 1000.0 / C_LOGIC_FREQUENCY ; Unused.

Const C_SMART_MISSILE_TEST_DISTANCE# = 10.0
Const C_SMART_MISSILE_TEST_ANGLE# = 60.0
Const C_SMART_MISSILE_NO_TURN_DISTANCE# = 15.0

Global timer = CreateTimer( C_LOGIC_FREQUENCY )

Graphics3D 800, 600, 0, 2
SetBuffer BackBuffer()

SeedRnd MilliSecs()

Global cam = CreateCamera()
CameraZoom cam, 1.6
MoveEntity cam, 0.0, 60.0, 0.0
TurnEntity cam, 90.0, 0.0, 0.0

Global light = CreateLight()

Global cone = CreateCone()
RotateMesh cone, 90.0, 0.0, 0.0
UpdateNormals cone
PositionEntity cone, 0.0, 0.0, -20.0

Global cube = CreateCube()
Global bcube = CreateCube()
EntityColor bcube,255,0,0
UpdateNormals cube
;PositionEntity cube, 40.0, 0.0, 20.0
PositionEntity cube, Rnd( -5.0, 5.0 ), 0.0, Rnd( -5.0, 5.0 )
Repeat
	PositionEntity bcube, Rnd( -15.0, 15.0 ), 0.0, Rnd( -15.0, 15.0 )
Until(EntityDistance(cube,bcube) > 8)


Global dist#

While Not KeyHit( 1 )
	
	dist# = EntityDistance( cone, cube )
	
	If allow_turn
		If dist# < C_SMART_MISSILE_TEST_DISTANCE#
			If Abs( DeltaYaw( cone, cube ) ) > C_SMART_MISSILE_TEST_ANGLE#
				allow_turn = False
			EndIf
		EndIf
	Else
		If dist# > C_SMART_MISSILE_NO_TURN_DISTANCE# Then allow_turn = True
	EndIf
	
	If Not avoid_entity( cone, bcube, 3.0, 0.5 ) Then
		If allow_turn Then YawToEntity cone, cube, 3.0
	EndIf
	
	MoveEntity cone, 0.0, 0.0, 0.5
	
	If dist# < 2.0
		PositionEntity cube, Rnd( -15.0, 15.0 ), 0.0, Rnd( -15.0, 15.0 )
		Repeat
			PositionEntity bcube, Rnd( -15.0, 15.0 ), 0.0, Rnd( -15.0, 15.0 )
		Until(EntityDistance(cube,bcube) > 8)
	EndIf
	
	UpdateWorld
	RenderWorld
	Flip
	
	WaitTimer( timer )
	
Wend

End


Function YawToEntity( src_entity, dest_entity, rate# )
; Turns 'src_entity' to point at 'dest_entity' at the rotation rate specified by 'rate#'.

	Local target_yaw# = DeltaYaw( src_entity, dest_entity )
	
	; If the required correction amount is less than the correction amount to be applied...
	If Abs( target_yaw# ) < rate#
		; Point 'src_entity' directly at 'dest_entity' to prevent jittering.
		TurnEntity src_entity, 0.0, target_yaw#, 0.0
	Else
		; Turn 'src_entity' gradually towards 'dest_entity'.
		TurnEntity src_entity, 0.0, rate# * Sgn( target_yaw# ), 0.0
	EndIf
End Function


Function avoid_entity( scr_entity, dest_entity, rate#, spd# )

	If EntityDistance(scr_entity,dest_entity) < 8 Then
		MoveEntity scr_entity,0,0,spd#
		dist1# = EntityDistance(scr_entity,dest_entity)
		MoveEntity scr_entity,0,0,-spd#
		TurnEntity scr_entity,0,rate#,0
		MoveEntity scr_entity,0,0,spd#
		dist2# = EntityDistance(scr_entity,dest_entity)
		MoveEntity scr_entity,0,0,-spd#
		TurnEntity scr_entity,0,-2*rate#,0
		MoveEntity scr_entity,0,0,spd#
		dist3# = EntityDistance(scr_entity,dest_entity)
		MoveEntity scr_entity,0,0,-spd#
		
		If dist1# > dist2# And dist1# > dist3# Then TurnEntity scr_entity,0,rate#,0
		If dist2# > dist3# And dist2# > dist1# Then TurnEntity scr_entity,0,2*rate#,0
		
		Return True
	Else
		Return False
	EndIf

End Function