; PhysicsBodyMass Example
; -----------------------
; Requires Extended mode.

Graphics3D 640,480,0,2
SetBuffer BackBuffer()

Const PHYSICS_STATIC=0
Const PHYSICS_DYNAMIC=2

camera=CreateCamera()
PositionEntity camera,0,3,-9

light=CreateLight()
RotateEntity light,45,-30,0
AmbientLight 50,50,50

; Independent Box3D world with Earth-like gravity
world=CreatePhysicsWorld()
PhysicsGravity world,0,-9.81,0

; Blue static ground slab
ground=CreateCube()
ScaleEntity ground,4,0.5,4
PositionEntity ground,0,-0.5,0,True
EntityColor ground,80,160,255
ground_body=CreatePhysicsBody(world,ground,PHYSICS_STATIC)
ground_shape=PhysicsBodyBox(ground_body,8,1,8,0)

; Orange crate whose density - and so mass - you can change
density#=1
crate=CreateCube()
ScaleEntity crate,0.5,0.5,0.5
PositionEntity crate,0,0.5,0,True
EntityColor crate,255,120,70
crate_body=CreatePhysicsBody(world,crate,PHYSICS_DYNAMIC)
crate_shape=PhysicsBodyBox(crate_body,1,1,1,density)

While Not KeyDown(1)

    ; Keys 1/2/3 rebuild the shape with a new density
    new_density#=0
    If KeyHit(2) Then new_density=0.5
    If KeyHit(3) Then new_density=1.0
    If KeyHit(4) Then new_density=4.0
    If new_density>0
        density=new_density
        FreePhysicsShape crate_shape
        crate_shape=PhysicsBodyBox(crate_body,1,1,1,density)
    EndIf

    ; Space kicks with a FIXED impulse - heavier crates jump less
    If KeyHit(57) Then PhysicsBodyImpulse crate_body,0,4,0

    ; Advance the Box3D simulation by one 60 Hz step
    StepPhysics world,1.0/60.0,4

    ; Read the mass Box3D calculated from shape volume times density
    mass#=PhysicsBodyMass(crate_body)

    ; Arrow keys move the camera
    If KeyDown(200) Then MoveEntity camera,0,0,0.1
    If KeyDown(208) Then MoveEntity camera,0,0,-0.1
    If KeyDown(203) Then TurnEntity camera,0,1,0
    If KeyDown(205) Then TurnEntity camera,0,-1,0

    RenderWorld

    Text 0,0,"1/2/3: density   Space: fixed kick   Arrow keys: camera   Esc: exit"
    Text 0,20,"Density: "+density+"   PhysicsBodyMass = "+mass+" kg"

    Flip

Wend

FreePhysicsWorld world
FreeEntity crate
FreeEntity ground
End