Apple Motion 3 - Manual (Page 709)

Chapter 8 Working with Particles 709
In the next illustrations, the group that contains the emitter is rasterized. The
rasterization is triggered by turning on Four Corner in the Group’s Properties tab. The
emitter’s Add blend mode no longer interacts with the group beneath it in the layer
stack. Notice that the icon for the rasterized group now appears with a frame around
its icon. This is called a rasterization frame.
In addition, when a 3D group—a group or a 3D emitter—is rasterized, the group as a
whole can no longer intersect with objects outside of the group. The rasterized 3D
group is treated as a single object and uses layer order, rather than depth order, to
composite the project. In the following illustration on the left, the nonrasterized group
that contains the particle emitter intersects with images from another group (when
Render Particles is set to In Global 3D). In the illustration on the right, a Bloom filter
applied to the particles group has triggered a rasterization, so the emitter no longer
intersects with images from another group.
The group containing the emitter is rasterized,
indicated by the frame around its icon. The emitter blend mode no longer interacts
with the group beneath it in the project.
3D particles before the group is rasterized. The
two orange texture movies exist in another
group that is interacting with the emitter. The particles after the group is rasterized. The
particles now exist in their own 3D world and
no longer intersect with objects outside of their
own group. Because the movie group is
underneath the particles group in the Layers
list, it appears behind the particles.