Masks to Cropped Layers works on After Effects layers that hold multiple masks, such as artwork pasted from Illustrator or areas tracked in Mocha. Each mask on the layer becomes a new layer carrying only one mask, created either as a solid or a pre-comp, and the new layer is cropped to the calculated size of that mask.
The utility has two main purposes. When animating vector artwork, it separates the masks into individual solids, and each new layer can take a stroke or fill effect and be animated like any conventional After Effects layer. For VFX work such as rotoscoping, clean-ups, or tracking confined to a small area of the plate, it creates pre-comps cropped to the mask size; using these as the source for effects work runs faster and gives longer RAM previews. In both cases the goal is to stop After Effects processing pixels that aren't used.
Mask sizes can be calculated from basic rectangles or from bezier paths, and measured from a single frame, the composition work area, or the layer's duration. New layers can be padded out, and position values rounded to integers.