This demo - not by me, BTW - may be of some use?
[edit] Actually, I've just seen some 'sticky' collisions happening when 2 balls hit, so there must be a bugette somewhere. Like I said, not my code so I ain't fixing it. :)
Open in online IDE; ; Bouncing ball physics - by Vincent DeCampo 2/1/04 ; Const GRAVITY#=-.05 Const BALLS=1 Graphics3D 640,480 ;*** Type for Ball *** Type Ball_Object Field Entity Field Pivot Field x# Field y# Field z# Field dx# Field dy# Field dz# Field xMin# Field xMax# Field yMin# Field yMax# Field zMin# Field zMax# Field elasticity# Field friction# End Type ;*** Lets create the floor *** Room=CreateTerrain(64) PositionEntity room,-32,0,-32 EntityColor Room, 0, 150, 0 ;******* Create Initial Ball ****** Blitz.Ball_Object = New Ball_Object InitBallVars(Blitz) Collisions BALLS, BALLS, 1, 2 ;***** Create Camera ***** camera=CreateCamera() PositionEntity camera,0,5,-40 PointEntity camera, Blitz\Entity ;********************************** ; Main Loop ;********************************** ; While Not KeyHit(1) If KeyHit(57) Then ;***** Seed RND Generator ***** SeedRnd (MilliSecs()) ;*** Create New Ball *** Blitz.Ball_Object = New Ball_Object InitBallVars Blitz End If ;**** Perform Room Physics **** For Ball.Ball_Object = Each Ball_Object BallPhysics (Ball) Next UpdateWorld ;**** Perform Ball-on-Ball Physics **** CheckCollisions (Blitz) RenderWorld RenderWorld Text 0,5,"Press SPACE to throw another ball" Text 0,15,"Press ESC to Exit" + TrisRendered() Flip 1 Wend End Function Flipper() While ScanLine()<>0: Wend Flip False End Function ;********************************** Function CheckCollisions (Ball.Ball_Object) For C.Ball_Object = Each Ball_Object If EntityCollided(c\Entity, BALLS) For i = 1 To CountCollisions(c\Entity) Ent=CollisionEntity (c\Entity, i) ;Get the normal of the surface which the entity collided with. Nx# = CollisionNX(c\Entity, i) Ny# = CollisionNY(c\Entity, i) Nz# = CollisionNZ(c\Entity, i) ;Compute the dot product of the entity's motion vector And the normal of the surface collided with. VdotN# = (c\dx# * Nx# + c\dy# * Ny# + c\dz# * Nz#) ;Calculate the normal force. NFx# = -2.0 * Nx# * VdotN# NFy# = -2.0 * Ny# * VdotN# NFz# = -2.0 * Nz# * VdotN# ;Add the normal force to the direction vector. c\dx# = c\dx# + NFx#/2 c\dy# = c\dy# + NFy#/2 ;Force /2 assumes balls equal in mass c\dz# = c\dz# + NFz#/2 For Hit.Ball_Object = Each Ball_Object If Hit\Entity = Ent Then ;Add negative force to collision entity vector Hit\dx# = Hit\dx# - NFx#/2 Hit\dy# = Hit\dy# - NFy#/2 ;Force /2 assumes balls equal in mass Hit\dz# = Hit\dz# - NFz#/2 End If Next Next EndIf Next End Function ;********************************** Function InitBallVars(Ball.Ball_Object) ;Create Ball Ball\Entity=CreateSphere() ScaleEntity Ball\Entity, 1,1,1 EntityType Ball\Entity, BALLS ;txt=LoadTexture("blitzlogo.bmp") ;EntityTexture Ball\Entity, txt ;Create Pivot Ball\Pivot=CreatePivot() ;*** Variables for Ball *** Ball\x#=0 Ball\y#=20 ;set ball 20 units above floor Ball\z#=0 Ball\dx#=Rand(5) Ball\dy#=0 ;at rest Ball\dz#=Rand(5) Ball\yMin#=1 Ball\yMax#=9999 Ball\xMin#=-32 Ball\xMax#=32 Ball\zMin#=-32 Ball\zMax#=32 Ball\elasticity#=.75 ;value from >0 to <1 (1=pure elastic collision) Ball\friction#=.01 ;************************** End Function ;********************************** Function BallPhysics (Ball.Ball_Object) If ball\y =< Ball\yMin# Then Ball\y = Ball\yMin# Ball\dy = -Ball\dy Ball\dy = Ball\dy * Ball\elasticity End If If Ball\x =< Ball\xMin# Then Ball\x = Ball\xMin# Ball\dx = -Ball\dx Ball\dx = Ball\dx * Ball\elasticity UpdatePivot (Ball) End If If Ball\x >= Ball\xMax# Then Ball\x = Ball\xMax# Ball\dx = -Ball\dx Ball\dx = Ball\dx * Ball\elasticity UpdatePivot (Ball) End If If Ball\z =< Ball\zMin# Then Ball\z = Ball\zMin# Ball\dz = -Ball\dz Ball\dz = Ball\dz * Ball\elasticity UpdatePivot (Ball) End If If Ball\z >= Ball\zMax# Then Ball\z = Ball\zMax# Ball\dz = -Ball\dz Ball\dz = Ball\dz * Ball\elasticity UpdatePivot (Ball) End If If Ball\y >= Ball\yMin# Then Ball\dy = Ball\dy + GRAVITY End If Ball\x = Ball\x + Ball\dx Ball\z = Ball\z + Ball\dz Ball\y = Ball\y + Ball\dy Ball\dx = Ball\dx - (Ball\dx*Ball\friction) Ball\dz = Ball\dz - (Ball\dz*Ball\friction) ;Move ball to new coords PositionEntity Ball\Entity, Ball\x, Ball\y, Ball\z, 0 ;Rotate mesh to give appearance of rolling TurnEntity Ball\Entity, Ball\dz*50,0,-Ball\Dx*50, 1 End Function Function UpdatePivot (Ball.Ball_Object) ;Move pivot to coords + deltas PositionEntity Ball\Pivot, Ball\x+Ball\dx, Ball\y+Ball\dy, Ball\z+Ball\dz PointEntity Ball\Entity, Ball\Pivot, 0 End Function
[edit] Actually, I've just seen some 'sticky' collisions happening when 2 balls hit, so there must be a bugette somewhere. Like I said, not my code so I ain't fixing it. :)