> Jason Merrill wrote: > I am drawing a bezier curve using: > > mySprite.graphics.curveTo(X1, Y1, X2, Y2); > > Works, and so I know where the control point is, and the desintation > point, but is there a way to calculate a point midway along the curve? > I'd like to position a sprite there. Hi Jason, The findPointOnCurve function (shown below) will give you exactly what you need. Just plug in your coordinates. Use a value of .5 for t to return the curve's midpoint. The findPointOnCurve function is used by Zeh Fernando's mc_tween2.as for the MovieClip.bezierSlideTo(...). I have also been successful adapting it for use in conjunction with Jack Doyle's TweenLite.as (http://www.greensock.com) for tweening an arc. private function findPointOnCurve(p1x:Number, p1y:Number, cx:Number, cy:Number, p2x:Number, p2y:Number, t:Number):Object { // From Zeh Fernando's mc_tween2.as (http://hosted.zeh.com.br/mctween/) // Returns the points on a bezier curve for a given time (t is 0-1); // This is based on Robert Penner's Math.pointOnCurve() function return {x:p1x + t*(2*(1-t)*(cx-p1x) + t*(p2x - p1x)), y:p1y + t*(2*(1-t)*(cy-p1y) + t*(p2y - p1y))}; } // Usage: mySprite.graphics.clear(); mySprite.graphics.lineStyle(3, 0x00FF00, 100); mySprite.graphics.moveTo(start.x, start.y); mySprite.graphics.curveTo(control.x, control.y, finish.x, finish.y); var p:Object = findPointOnCurve(start.x, start.y, control.x, control.y, finish.x, finish.y, .5); mySprite.graphics.lineStyle(10, 0xFF0000, 100); mySprite.graphics.moveTo(p.x, p.y); mySprite.graphics.lineTo(p.x + 1, p.y - 1); HTH Regards,
-Keith http://keithreinfeld.home.comcast.net _______________________________________________ Flashcoders mailing list Flashcoders@chattyfig.figleaf.com http://chattyfig.figleaf.com/mailman/listinfo/flashcoders
