Adobe After Effects CS3 - Manual (Page 180)

AFTER EFFECTS CS3
User Guide
175
How render order and collapsed transformations affect 3D layers
The positions of certain kinds of layers in the layer stacking order in the Timeline panel prevent groups of 3D layers
from being processed together to determine intersections and shadows.
A shadow cast by a 3D layer does not affect a 2D layer or any layer that is on the other side of the 2D layer in the layer
stacking order. Similarly, a 3D layer will not intersect with a 2D layer or any layer that is on the other side of the 2D
layer in the layer stacking order. No such restriction exists for lights.
3D layers intersecting (left), and 3D layers prevented from intersecting by intervening 2D layer (right)
Just like 2D layers, other types of layers also prevent 3D layers on either side from intersecting or casting shadows on
one another:
• An adjustment layer
• A 3D layer with a layer style applied
• A 3D precomposition to which an effect, closed mask (with mask mode other than None), or track matte has been
applied
• A 3D precomposition layer without collapsed transformations
A precomposition with collapsed transformations (Collapse Transformations switch selected) does not interfere
with the interaction of 3D layers on either side—as long as all of the layers in the precomposition are themselves 3D
layers. Collapsing transformations exposes the 3D properties of the layers that compose the precomposition. Essen-
tially, collapsing transformations in this case allows each 3D layer to be composited into the main composition
individually, rather than creating a single 2D composite for the precomposition layer and compositing that into the
main composition. The tradeoff is that this setting removes your ability to specify certain layer settings for the
precomposition as a whole—such as blending mode, quality, and motion blur.
Shadows cast by continuously rasterized 3D layers (including text layers) are not affected by effects applied to that
layer. If you want the shadow to show the results of the effect, then precompose the layer with the effect.
To ensure that the shadow remains where expected on a 3D layer with a track matte, precompose the 3D layer and
the track matte layer together (but don’t collapse transformations), and then apply the shadow to the precomposition.
Effects on continuously rasterized vector layers with 3D properties are rendered in 2D and then projected onto the
3D layer. OpenGL rendering does not support this sort of projection, so results may differ when rendering using
OpenGL. This projection does not occur for compositions with collapsed transformations.