Color Override/Ray Type Switcher (mental ray)

Allows different types of rays to return different results.

“Eye rays” are the primary rays; the other ray types are considered secondary.

Note: In ray tracing, the "eye rays" are the rays cast directly from the camera to render the image. One eye is cast per pixel in the final image.

One use of this shader is to specify different environments, depending on the type of ray:

Another use of the Color Override/Ray Type Switcher can be to eliminate color bleeding in the scene.

Wood grain on floor causes color bleeding on the walls, especially at the right of the scene.

The solution is to use a Color Override/Ray Type Switcher, and wire the diffuse map so it affects Eye Rays only.

Color Override/Ray Type Switcher restricts the effect of a bitmap to Eye Rays only.

When the bitmap affects Eye Rays only, color bleeding is gone.

Note: If several surfaces with different materials cause color bleeding, you might need more work and more experimentation to eliminate the bleeding.

Interface

Color Override/Ray Type Switcher Parameters rollout

Default

Sets the default shader: If another ray type does not have a shader explicitly specified, this shader is used.

Eye Rays

Sets the shader used for eye rays.

Transparency

Sets the shader used for transparency.

Reflections

Sets the shader used for reflections.

Refraction

Sets the shader used for refraction.

Shadows

Sets the shader used for shadows.

Environment & Indirect Illumination Override rollout

Final Gather

Sets the shader used for Final Gather.

Photons

Sets the shader used for photons.

Environment

Sets the shader used for the environment. This is distinct from the Eye Ray shader: It is used for secondary rays unless those are assigned a shader of their own.