User Guide

CHAPTER 9
304
3D Compositing
After Effects renders the X, Y, and Z rotation Transform properties in their descending Time-
line order, regardless of the original order in which you set those Transform properties.
Note: After Effects does not render intersecting layers.
Rendering compositions containing both 2D and 3D layers
If compositions contain both 2D and 3D layers, After Effects renders the 3D layers in
independent, noninteractive groups that are separated by the 2D layers.
For example, if the Timeline contains (from top to bottom) two 3D layers, two 2D layers,
then two final 3D layers, After Effects first renders the bottom two 3D layers as a set,
according to their spatial order in the Composition window. Next, it renders the 2D layers
according to their Timeline order, from bottom to top. Finally, it renders the Timeline’s
top set of 3D layers.
However, this top set of 3D layers is rendered in a geometric space independent of the
lower Timeline set of 3D layers. In effect, the 2D layers have split the 3D space into iden-
tical, but separate universes. The result is that shadows cast by either Timeline set of 3D
layers do not fall on the other set, and the two sets of 3D layers do not interact geometri-
cally. For example, if the animation calls for a single 3D layer to pass in front of a second
3D layer and cast a shadow on the second layer as it passed, then this occurs if there is not
a 2D layer between them in the Timeline. However, if there is a 2D layer between them
(and it is small enough to allow you to see both 3D layers in the Composition window),
then the 3D layers are rendered in separate 3D universes, and, therefore the first layer does
not pass in front of the second and does not cast a shadow upon it. Instead, though the
animation will still occur, it will happen on separate sides of the 2D layer.
The sets of 3D layers do, however, share both cameras and lights, since these two elements
are global to the composition.
UG.book Page 304 Wednesday, February 21, 2001 12:05 PM