; PhysicsBodyTerrain 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

; Bowl-shaped terrain centred under the camera
terrain=CreateTerrain(8)
ScaleEntity terrain,0.75,2,0.75
PositionEntity terrain,-3,-1,-3,True
For z=0 To 8
    For x=0 To 8
        ModifyTerrain terrain,x,z,0.05+((x-4)*(x-4)+(z-4)*(z-4))*0.0125
    Next
Next

; Build a static height field from the terrain and its scale
terrain_body=CreatePhysicsBody(world,terrain,PHYSICS_STATIC)
terrain_shape=PhysicsBodyTerrain(terrain_body,terrain)

; Orange ball dropped off-centre so it rolls around the bowl
ball=CreateSphere()
ScaleEntity ball,0.5,0.5,0.5
PositionEntity ball,1.5,2,0,True
EntityColor ball,255,120,70
ball_body=CreatePhysicsBody(world,ball,PHYSICS_DYNAMIC)
ball_shape=PhysicsBodySphere(ball_body,1,1)
PhysicsShapeRestitution ball_shape,0.4

While Not KeyDown(1)

    ; Space bounces the ball up so it lands in a new hollow
    If KeyHit(57) Then PhysicsBodyImpulse ball_body,0,2,0

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

    ; Respawn the ball if it rolls off the terrain edge
    If EntityY(ball)<-6
        FreePhysicsBody ball_body
        PositionEntity ball,1.5,2,0,True
        ball_body=CreatePhysicsBody(world,ball,PHYSICS_DYNAMIC)
        ball_shape=PhysicsBodySphere(ball_body,1,1)
        PhysicsShapeRestitution ball_shape,0.4
    EndIf

    ; 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: bounce the ball   Esc: exit"
    Text 0,20,"The ball rolls on a Box3D height field built from the terrain"

    Flip

Wend

FreePhysicsWorld world
FreeEntity ball
FreeEntity terrain
End