This shader passes a color value through the render tree and shares the output among other nodes connected to its input channels.
These channels are "dummy" inputs that get called and evaluated, but do not have an effect on the final rendered output in the render tree. The primary purpose of these channel ports is to connect multiple Store In Channel shaders, all of which can share (or rather store) the data passing through the node's main input port. For more information, see Data > Render Channel.
It is important to note that by default, mental ray clips color samples after each ray, before filtering them into the final pixel value. The Clip alpha below RGB mode first clips RGB values to the 0 to 1 range, and then clips alpha values to the MaxRGB to 1 range. If you need to preserve RGB color and intensity as well as accurate transparencies, you can set the Color Channel Clipping option to No Clip in the Framebuffer > Motion Data settings of the mental ray Render Options Property Editor.
