2D Physics: Ideas for a Community Project

This is a little off topic but here is a simple Circle-Circle Collision routine for you to use.

Strict


Global CollisionObjectList:TList = CreateList()

Const COLL_DISABLED:Int = 0
Const COLL_STATIC:Int = 1
Const COLL_DYNAMIC:Int = 2

Global COLL_FRICTION:Float = 1.0
Global COLL_BOUNCE:Float = 1.0

Const COLL_CIRCLE:Int = 0

Type TCollisionObject
	Field Position:TVector2
	Field Velocity:TVector2
	Field Acceleration:TVector2

	Field LastCollider:TCollisionObject
	Field SeperationVector:TVector2
	
	Field Kind:Int
	Field Response:Int
	Field Radius:Float
	Field width:Float
	Field height:Float
	
	Method New()
		CollisionObjectList.AddLast(Self)
		SeperationVector = TVector2.Create()
		Position = TVector2.Create()
		Velocity = TVector2.Create()
		Acceleration = TVector2.Create()
	End Method
	
	Function CreateCircle:TCollisionObject(_parent:Object,_Response:Int,_Radius:Float,_X:Float = 0,_Y:Float = 0)
		Local Collider:TCollisionObject = New TCollisionObject
		Collider.Kind = COLL_CIRCLE
		Collider.Response = _Response
		Collider.Radius = _Radius
		Collider.width = _Radius * 2
		Collider.height = _Radius * 2
		Collider.Position.x = _X
		Collider.Position.Y = _Y
		Return Collider
	End Function
	
	Method Collision()
		LastCollider = Null
		For Local Collider:TCollisionObject = EachIn CollisionObjectList
			If Collider <> Self
			
				Select Collider.Kind
					Case COLL_CIRCLE
						Local _Distance:Float = sqr((Collider.Position.x-Position.x)*(Collider.Position.x-Position.x) + (Collider.Position.Y-Position.Y)*(Collider.Position.Y-Position.Y))
						If _Distance <= Collider.Radius + Radius 
							
							LastCollider = Collider
					
							Local _SeperationVector:TVector2 = TVector2.Create(Collider.Position.x-Position.x,Collider.Position.Y-Position.Y)
							Local _Angle:Float = _SeperationVector.Angle()
							
							_SeperationVector.x = Cos(_Angle) * (_Distance - (Radius+Collider.Radius)-1)
							_SeperationVector.Y = Sin(_Angle) * (_Distance - (Radius+Collider.Radius)-1)

							SeperationVector.x :+ _SeperationVector.x
							SeperationVector.Y :+ _SeperationVector.Y
						End If
				End Select
			End If
		Next
	End Method
	
	Method Render()
		SetColor 0,255,0
		If LastCollider SetColor 255,0,0
		Select Kind
			Case COLL_CIRCLE
				DrawOval Position.x-Radius,Position.Y-Radius,width,height
		End Select
		SetColor 255,255,255
	End Method
	
	Method Update()
		Velocity.AddVector(Acceleration)
		Position.AddVector(Velocity)
		
		Collision()

		If LastCollider
			Local BounceAngle:Float = SeperationVector.Angle()
			Local BounceLength:Float = Velocity.length()
			Local BounceVector:TVector2 = New TVector2
			BounceVector.x = Cos(BounceAngle) * BounceLength
			BounceVector.Y = Sin(BounceAngle) * BounceLength				
			BounceVector.Mult(COLL_BOUNCE)

			Velocity.Mult(COLL_FRICTION)		
			Velocity.AddVector(BounceVector)

			Position.AddVector(SeperationVector)
			SeperationVector.Set(0,0)
		End If
	End Method

End Type

Type TVector2
	Field X:Float, Y:Float
	Function Create:TVector2 (_X:Float = 0, _Y:Float = 0)
		Local _V:TVector2 = New TVector2
		_V.X = _X
		_V.Y = _Y
		Return _V
	End Function   
	Method Set (_X:Float, _Y:Float)
		X  =  _X
		Y  =  _Y
	End Method
	Method AddVector (_V:TVector2)
		X :+ _V.X
		Y :+ _V.Y
	End Method
	Method Mult (_M:Float)
		X :* _M
		Y :* _M
	End Method
	Method length:Float ()
		Return sqr(X * X + Y * Y)
	End Method
	Method Angle:Float ()
		Return ATan2 (Y, X)
	EndMethod
End Type

Local CO:TCollisionObject = TCollisionObject.CreateCircle(Null,COLL_DYNAMIC,25,100,100)  

For Local I:Int = 1 to 10
	TCollisionObject.CreateCircle(Null,COLL_STATIC,Rnd(10,50),Rnd(0,640),Rnd(100,380))
Next

Graphics 640,480,0

While not KeyHit(KEY_ESCAPE)
	Cls

	CO.Acceleration.x = (KeyDown(KEY_RIGHT) - KeyDown(KEY_LEFT))*.08
	CO.Acceleration.Y = (KeyDown(KEY_DOWN) - KeyDown(KEY_UP))*.08
	
	If MouseDown(1)
		CO.Position.Set(MouseX(),MouseY())
		CO.Velocity.Set(0,0)
	End If
	               
	For Local CollisionObject:TCollisionObject = EachIn CollisionObjectList
		CollisionObject.Update
		CollisionObject.Render
	Next

	Flip
	FlushMem
Wend