Apple Motion 4 - Manual (Page 1399)

Shadows and Rasterization
Rasterized 3D objects do not cast shadows. If you perform an action that causes a group
to be rasterized (such as modifying the group opacity or enabling the glow setting for a
text object) and you still want that group to cast a shadow, you must flatten the group.
Flattened groups act as 2D layers and can cast and receive shadows as long as they are
themselves embedded in a 3D group. Text objects are flattened in the Layout pane of
the Text Inspector, and 3D groups are flattened in the Group tab of the Inspector. Particle
systems and Replicators are flattened by deselecting the 3D checkbox in the Emitter or
Replicator tab.
Remember that rasterizing causes layers to be rendered in the stacking order shown in
the Layers tab. So even if the shadow-casting object is in front of the shadow-receiving
object in the Canvas, rasterizing it may cause it to change position to reflect the relative
order of the layers in the Layers tab. You may need to rearrange the layer order in the
Layers tab to enable the rasterized, flattened object to cast a shadow.
For more on working with Shadows, see Shadows .
1399 Appendix A About Rasterization