I'm far from an expert in AE. This problem is baffling to me. I cut and pasted vector paths from Illustrator into a shape layer. Then I stroked and trimmed the paths, animating the lines to "draw onto" the screen. The problem is in preview. The animation will preview ONLY if RAM preview is set on full resolution. At other resolutions the lines don't show. In any resolution the lines show when stepping through the timeline. Obviously, the work-around is that I always have preview in full res, but make it less of a RAM hog by skipping 1 frame in preview. Any idea why I have this preview problem with trimmed paths?
Smaller resolutions mean you are seeing less pixels, if your paths are small enough---they maybe be discarded in resolution drop. I'm not 100% sure, but I think it has to do with the size of the stroke and how AE does the res drop-down. Increase the width of the stroke and test it out.
Johnny Cuevas, Editor
"I have not failed 700 times. I have succeeded in proving that those 700 ways will not work. When I have eliminated the ways that will not work, I will find the way that will work."
---THOMAS EDISON on inventing the light bulb.