Beam

The Beam shader provides a quick means to get atmospheric effects from light sources. Halos around bright lights, sunbeams from windows, and light cones from spotlights are typical examples of the Beam shader in action.

Unlike most other volumic lighting shaders, Beam is ultra-fast: tests on typical scenes show that Beam adds less than 10% to the rendering time. This speed is achieved by eliminating shadow calculations; this means that when shadows are necessary, the artist is responsible creating geometry for the beam's area of effect.


Procedure

On a point light

Create a point light with Light->Define.

Choose Atmosphere->Depth Fading...

Turn on depth fading, and select Beam as the depth fading shader.

In the Beam dialogue box, click the Select button and choose the point light.

On a spot light

Create a spotlight with Light->Define.

Get a cone with Get->Primitive->Cone.

Scale and position the cone so that it exactly overlaps the light's cone.

In the cone's Material dialogue box, set the transparency to 1.

Again in the cone's Material dialogue box, select Beam as the volume shader.

In the Beam dialogue box, click the Select button, and choose the spotlight.


Parameters


Fog Density allows the artist to adjust the "thickness" of the fog surrounding the light source. Larger values cause the beam to be bigger and brighter; smaller values cause the beam to be smaller and dimmer.

Color sets the color of the virtual fog particles, which will effect the color of the beam. The final color of the beam is determined by both the color of the particles and the color of the lights.

Lights specifies which lights should produce beams.