Freezing your Roto Brush tool results
You’ve put a fair amount of time and effort into creating the segmentation boundary across the entire clip. After Effects has cached the segmentation boundary so it can recall it without having to make the calculations again. To keep that data easily accessible, you’ll freeze it. This reduces the processing demands on your system so you can work faster in After Effects.
Once the segmentation is frozen, you cannot edit it unless you unfreeze it. Refreezing the segmentation is time-consuming, so it’s best to refine the segmentation boundary as much as possible before freezing.
Click the Freeze button in the lower right area of the Layer panel.
After Effects displays a progress bar as it freezes the Roto Brush and Refine Edge tool data. Freezing may take a few minutes, depending on your system. As After Effects freezes the information for each frame, the cache line turns blue. When it has finished freezing, a blue warning bar appears above the time ruler in the Layer panel, reminding you that the segmentation is frozen.
Click the Toggle Alpha Boundary button () in the Layer panel to see the matte. Then click the Toggle Transparency Grid button (). Move the time marker across the time ruler to see the subject without the distractions of the background.
Click the Toggle Alpha Boundary button again to see the boundary.
Choose File > Save.
After Effects saves the frozen segmentation information with the project.