; FreePhysicsJoint 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,-8

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 for the cut arm to land on
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)

; Blue static anchor block near the top of the scene
anchor=CreateCube()
ScaleEntity anchor,0.25,0.25,0.25
PositionEntity anchor,0,4,0,True
EntityColor anchor,80,160,255
anchor_body=CreatePhysicsBody(world,anchor,PHYSICS_STATIC)
anchor_shape=PhysicsBodyBox(anchor_body,0.5,0.5,0.5,0)

; Orange pendulum arm hinged to the anchor
arm=CreateCube()
ScaleEntity arm,0.25,1,0.25
PositionEntity arm,0,2.75,0,True
EntityColor arm,255,120,70
arm_body=CreatePhysicsBody(world,arm,PHYSICS_DYNAMIC)
arm_shape=PhysicsBodyBox(arm_body,0.5,2,0.5,1)
hinge=CreatePhysicsHingeJoint(anchor_body,arm_body,0,3.75,0,0,0,1)

; Start the pendulum swinging
PhysicsBodyImpulse arm_body,1.5,0,0

While Not KeyDown(1)

    ; Space cuts the joint, or rebuilds the pendulum after a cut
    If KeyHit(57)
        If hinge<>0
            ; Free the joint - the arm drops away from the anchor
            FreePhysicsJoint hinge
            hinge=0
        Else
            ; Rebuild the arm body and re-hinge it to the anchor
            FreePhysicsBody arm_body
            PositionEntity arm,0,2.75,0,True
            RotateEntity arm,0,0,0
            arm_body=CreatePhysicsBody(world,arm,PHYSICS_DYNAMIC)
            arm_shape=PhysicsBodyBox(arm_body,0.5,2,0.5,1)
            hinge=CreatePhysicsHingeJoint(anchor_body,arm_body,0,3.75,0,0,0,1)
            PhysicsBodyImpulse arm_body,1.5,0,0
        EndIf
    EndIf

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

    ; 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,"Arrow keys: move camera   Space: cut / rebuild joint   Esc: exit"
    If hinge<>0
        Text 0,20,"Hinge joint handle: "+hinge+"   (swinging)"
    Else
        Text 0,20,"Joint freed - the arm falls under gravity"
    EndIf

    Flip

Wend

FreePhysicsWorld world
FreeEntity arm
FreeEntity anchor
FreeEntity ground
End