Apple Motion 2 Tutorials - Manual (Page 172)

172 Tutorial 4 Working With Particles
Because the current blend mode of the Blue Lights emitter object is Normal, the
background does not show through the particles.
11 Move the playhead to frame 30.
Adding color values together within the particle system gives it more punch. Adding
the color values of the particles layer to those of the background better integrates the
two elements.
Changing the Blend Mode of the Layer
Change the blend mode of the layer so that the background can be seen through the
particles.
To change the blend mode of the particles layer:
1 Select the particles layer in the Canvas or Layers tab.
2 In the Inspector, click the Properties tab.
Additive Blend
The Additive Blend parameter can have a dramatic effect on the look of a particle
system. By default, Blue Lights has Additive Blend turned on. In the Emitter tab of the
Inspector, click the Additive Blend checkbox to turn it off.
Notice that when Additive Blend is turned off, the entire particle system darkens.
Turning it back on intensifies the colors and makes them brighter. This is because
Additive Blend adds the color values of overlapping particles together. Any time one
particle overlaps another, higher (brighter) color values are created. Click the Additive
Blend checkbox again to turn it back on.
Additive Blend on Additive Blend off