Adobe After Effects CS4 - Manual (Page 72)

66 USING AFTER EFFECTS CS4
Projects and compositions
Last updated 12/21/2009
When a closed mask (with mask mode other than None), a layer style, or an effect is applied to a nested composition
with collapsed transformations, the layers in the nested composition are first rendered on their own, then masks and
effects are applied, and then the result is composited into the main composition. This rendering order means that the
blending modes of the nested layers are not applied to any underlying layers in the main composition, and that 3D
layers above and below the collapsed layer cannot intersect or cast shadows on each other.
More Help topics
“ 3D layer interactions, render order, and collapsed transformations ” on page 184
“ Change the stacking order for selected layers ” on page 144