AE跟随线条拖尾MG动画教程 After Effects Vector Shape Layer Trails Tutorial通过表达式来控制生成拖尾线条效果，MG动画十分有用的小技巧In this tutorial, Mikey Borup walks us through the process of creating cool looking vector shape layer trails inside of Adobe After Effects.

用到的表达式：D=Math.sqrt(value[0]*value[0]+value[1]*v­alue[1]);rot=radiansToDegrees(Math.atan2(value[1]­,value[0]))XS=transform.scale[0]/100;YS=transform.scale[1]/100;TC=Math.cos(degreesToRadians(rotation+ro­t));TS=Math.sin(degreesToRadians(rotation+ro­t))*.9;[D*TC*XS,D*TS*YS]+position