After Effects Roto Brush Tips
This helpful information was discussed recently on the After Effects Mailing List. The roto brush is such a helpful tool but it really pays to understand how it works. Check out these tips to aid in your roto brushing. Thanks to Chris Meyer and Teddy Gage for the advice!
- Roto Brush has to propagate from the Base Frame outward. Placing the initial base frame closer to the middle instead of the start of the clip, and/or creating multiple Base Frames, results in shorter spans that may need to be propagated.
- Once you have Segmentation Boundary you’re happy with, click the Freeze button in the lower right of the Layer Panel to pre-calculate and store the time-consuming propagation.
- Before you start, pick several base frames in your clip, each with defining poses the character holds. Lock in your tolerance and color estimation settings. Never have a span longer than 50-100 frames, it takes forever to propagate if you need to revise those frames. You create new base frames by painting on a frame outside the span range (under the layer frame timeline).
- Avoid revising frames whenever possible. Start work from each of your base frames and work sequentially frame to frame. DO NOT jump around between frames. This completely screws up the propagation.
- Enhance the contrast with a filter (like levels or curves) in the effect stack before doing the roto work. The rotobrush picks up on details better. When you are done, freeze the propagation and turn off the effect for rendering.
- Do not turn on smooth or refine mattes until you have finished and frozen the layers.
- Use absolutely the fewest strokes possible to create each matte. If you make a mistake, don’t paint over it. Undo it instead. Extra strokes mean extra processing and it can screw up the edge detection.
- Start with the largest brush in each frame and work progressively smaller. Let the rotobrush do the work, don’t waste time with small details that could be pulled out by changing your tolerance settings.