Apple Motion 4 - Manual (Page 1238)

Modifying the object in a way that causes rasterization prevents shadows from being
displayed.
In some cases you may be able to find another way to perform the effect that will not
require rasterization. For example, in the following images, rather than modifying the
opacity of the particle emitter, which causes rasterization, you can modify the opacity of
the particle cells, creating the desired effect and maintaining the desired shadows.
Emitter set to 100% Opacity Emitter set to 60% Opacity Particle cells set to 60% Opacity
Note that in the second figure, the layer order of the particle system has been affected,
and all particles now appear in front of the letter A. For more about how rasterization
affects shadows, see
Shadows and Rasterization .
Shadows Without Lights
Lighting and shadows can each be disabled independently. You can keep shadows visible,
even when lighting is disabled, allowing you to keep the original unshaded look of the
scene. Turning off lighting also changes the way shadows are rendered.
1238 Chapter 18 3D Compositing