ABSTRACT
Precompose is used primarily for nesting – grouping layers and manipulating the rendering order. The difference is that nesting implies moving up the hierarchy. Precomposing a single layer is used to solve the same sorts of often-unforeseen rendering order problems. The solution to problems with the default rendering order is to reverse the order of some events by spreading the layer across two comps, so one can pick and choose which step happens in which comp. The Pre-compose dialog offers two options: Leave all attributes in “current comp” , or Move all attributes to the new composition. Attributes refers to the values and keyframes for masks, effects, transformations, blending modes, layer styles, trimming, and so on. For a single layer, both options are available. An easy way around the misleading layer bar is to immediately trim the precomp layer’s in and out points after precomposing, to match the first and last active frames in the precomp.
