Bezier spline based animation controller

Community Forums/Showcase/Bezier spline based animation controller

Jay Kyburz (Posted 2005) [#1]

Hey all, Here is a Bezier spline based animation controller I've been working on. To use: 1. Create a controller 2. Add any number or keyframes or spline knots (They currently need to be added in time order) 3. Set the controllers Value property to a Varptr of the floating point value you want to move on the spline. 4. Call Update() on the controller every frame and pass through how much time has passed since the last update. My example program below is not very exciting but it shows the controller working. There are many possible optimizations that can be made but I probably won't bother making them unless I find I need more than a few hundred of them running at once in my game. This is the first code I have shared here on the forums. Please let me know if it sux so I can rip it down before to many people see it. :) Strict '------------------------------------------------ Type tAnimationKey Field Value :Float Field Time :Int ' these optional handles are used to control the direction of the curve ' as it approaches and leaves the key point. ' Should be reletave to the Value Field Field HandleInHeight :Float Field HandleOutHeight :Float End Type '------------------------------------------------ '------------------------------------------------ Type tAnimationController Field KeyArray :tAnimationKey[] Field Time :Int = 0 Field Value :Float Ptr Field Linear :Int = False Field Looping :Int = True ' add an animation key to the key array Method AddKey (_Time:Int=0,_Value:Float=0,_HandleInHeight:Float=0,_HandleOutHeight:Float=0) Local ak:tAnimationKey = New tAnimationKey ak.Value = _Value ak.Time = _Time ak.HandleInHeight= _HandleInHeight ak.HandleOutHeight= _HandleOutHeight Local i:Int = Self.KeyArray.Length Self.KeyArray = Self.KeyArray[..i+1] Self.KeyArray[i] = ak End Method ' called every frame and updated the pointer to the animating property Method Update(_delta:Int) Local i :Int = 0 Local key :Int = 0 Local curvePos :Float Self.Time :+ _delta 'Just loop now If Self.Time > Self.KeyArray[Self.KeyArray.Length - 1].Time Then If Self.Looping Then Time = Self.KeyArray[0].Time Else ' destroy me now End If ' find the key pair for the current time For i = 0 To Self.KeyArray.Length - 2 If (Self.Time > Self.KeyArray[i].Time) And (Self.Time <= Self.KeyArray[i+1].Time) key = i End If Next ' find where we are betwene the two keys. curvePos = (1.0/(Self.KeyArray[key+1].Time - Self.KeyArray[key].Time)) * (Self.Time - Self.KeyArray[key].Time) ' find the final value If Self.Linear Then Self.Value[0] = ((Self.KeyArray[key + 1].Value - Self.KeyArray[key].Value) * curvePos) + Self.KeyArray[key].Value Else Self.Value[0] = Self.Curve (Self.KeyArray[Key].Value, Self.KeyArray[Key].HandleOutHeight,.. Self.KeyArray[Key+1].Value, Self.KeyArray[Key+1].HandleInHeight,.. curvePos) End If 'linear End Method ' method creates a bezier curve and finds our value based on _mu ' direct port of c from net Method Curve:Float(_P1:Float,_HandleInHeight:Float,_P4:Float,_HandleOutHeight:Float,_mu:Float) Local mum1 :Float Local mum13 :Float Local mu3 :Float Local p :Float Local p2 :Float Local p3 :Float If _mu > 1 Then Return _p1 If _mu < 0 Then Return _p1 p2 = _p1 + _HandleInHeight p3 = _p4 + _HandleOutHeight mum1 = (1 - _mu) mum13 = mum1 * mum1 * mum1 mu3 = _mu * _mu * _mu p = mum13*_p1 + 3*_mu*mum1*mum1*p2 + 3*_mu*_mu*mum1*p3 + mu3*_p4 Return(p) End Method ' this method is used to visualise the curve Method Render(_TimeScale:Float=0.1, _ValueScale:Float=1, _r:Int=255, _g:Int=255, _b:Int=255, _lable:String="") SetColor (_r,_g,_b) DrawText (_lable,KeyArray[KeyArray.length-1].Time*_TimeScale,KeyArray[KeyArray.length-1].Value*_ValueScale) For Local i = 0 To KeyArray.length - 2 SetColor (_r-50,_g-50,_b-50) DrawRect (KeyArray[i].Time*_TimeScale-2, KeyArray[i].Value*_ValueScale-2,5,5) DrawRect (KeyArray[i+1].Time*_TimeScale-2, KeyArray[i+1].Value*_ValueScale-2,5,5) 'hack If Self.Linear Then DrawLine (KeyArray[i].Time*_TimeScale, KeyArray[i].Value*_ValueScale, KeyArray[i+1].Time*_TimeScale, KeyArray[i+1].Value*_ValueScale) SetColor (_r,_g,_b) Local TimeAcc:Float = KeyArray[i+1].Time - KeyArray[i].Time If Not Self.Linear Then For Local j:Float = 0.01 To 1 Step 0.02 Local ypos:Float = Curve (KeyArray[i].Value,KeyArray[i].HandleOutHeight,KeyArray[i+1].Value,KeyArray[i+1].HandleInHeight,j) Local xpos:Float = KeyArray[i].Time + (TimeAcc)* j Plot(xpos*_TimeScale,ypos*_ValueScale) Next EndIf Next EndMethod End Type '------------------------------------------------ Type tMovingBox Field x:Float = 0 Field y:Float = 200 Method Render() SetColor (50,200,50) DrawRect (x,y,15,15) End Method End Type Graphics 640,480 Global TimeNow :Int Global DeltaTime :Int Global Accumulator :Int Global LastFrameTime :Int Global TickRate :Int = 20 Global mb:tMovingBox = New tMovingBox ' create an animation controller Global ac1:tAnimationController = New tAnimationController ' add 4 keys ac1.AddKey (0000,200,0,0) ac1.AddKey (2100,300,0,0) ac1.AddKey (3000,300,0,0) ac1.AddKey (4000,200,0,0) ' bind the animation controller to the boxes y property ac1.Value = Varptr mb.y ' uncomment these to see the effect of the bezier handles ' dont forget to comment the other addKey calls. 'ac1.AddKey (0000,200,0,200) 'ac1.AddKey (2100,300,-200,0) 'ac1.AddKey (3000,300,0,0) 'ac1.AddKey (4000,200,300,0) Global ac2:tAnimationController = New tAnimationController ac2.AddKey (0,0) ac2.AddKey (4000,400) ac2.Linear = True ' ac2 is linear ac2.Value = Varptr mb.x While Not KeyHit (KEY_ESCAPE) TimeNow = MilliSecs() DeltaTime = TimeNow - LastFrameTime Accumulator :+ DeltaTime ' clamp needed for start up If Accumulator > 5 * TickRate Then Accumulator = 5 * TickRate While Accumulator > TickRate ' this is a fixed time step method Accumulator :- TickRate Cls ac1.Update(TickRate) ac2.Update(TickRate) ac1.Render (0.1, 1, 150, 0, 150, "ac1: Y: " + String(ac1.Value[0])) ac2.Render(0.1, 1, 150, 150, 0, "ac2: X: "+ String(ac2.Value[0])) mb.Render() Flip Wend Wend