I see no way to do it on one layer. Best solution I came up with is after you animate the line on, duplicate the layer and remove all the keyframes. Under shape change the direction of the arrow under “Path”, that changes the starting point of the path. Then animate the “End” from 100% to 0. Use that layer as a track matte for your dotted line.
Kind of a clunky work around, that wouldn’t be needed if you could keyframe the starting point of the layer. I made a sample project, you can check out.
8765_dottedlinetrackmatte.aep.zip
Johnny Cuevas, Editor
Thinkck.com
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—THOMAS EDISON on inventing the light bulb.