Use rays to simulate volumetric effects. You can attach a Rays object to a light in Action.
You can position rays behind 2D or 3D objects to generate effects, although rays are still visible even without an object to outline them. When semi-transparent objects are positioned in front of the light, it is possible to generate volumetric rays that use the colour of the object.
Tip: Use a GMask link to connect a GMask directly to the Rays node in the schematic. If you then select Use As Occluder in the Post Processing box in the GMask menu, you can create interesting effects by having the GMask occlude only the Rays effect.