How do I create those animated vector graphics effects make popular in MTV promos, in which a graphic simulates growth with patterns reveals itself in different stages. Something similar to animated hand writing.
I know it has something to do with animated mask, but I have tried, it is quite difficult to manage the mask to reveal different portion as intended.
An animated mask would work (it's a tried and true After Effects method).
But yeah, in Motion there's lots of ways to do stuff like this:
2) With Replicators and Behaviors, if you have Motion 3, check out Library>Content>Flora>Branch 01 which uses Replicated shapes and the Sequence Replicator to animate 'em
3) Shapes using Shape Behavior>Write On (in Motion 3, see Library>Content>Drawings>Ornament 01)
4) Particle Emitters! (cool, huh?) by animating a Particle Emitter's point of origin with a keyframed motion path (Inspector>Properties>Transform>Position) (in Motion 3, see Library>Content>Flora>Arabesque)
5) With Motion 3, you could use the new Paint Stroke Tool as well as the new Sequence Paint Behavior (Shape>Sequence Paint) to reveal paint strokes over time
5b) You could even create a animated mask with the Paint Stroke Tool (i.e., white paint strokes) and then utilize Stencil Luma, Stencil Alpha, etc. You can even edit the splines that make up the essentially vector "paint" strokes.