This operator implements a matte shader that occludes geometry behind the surface being rendered. The output image, however, will have the alpha value specified.
The output color is always zero and no lighting is applied.
The operator is well suited to compositing tricks. When the matte shader is hit by shadow rays, the shadow amount determines how much of a shadow will be cast by the surface, meaning that both the opacity and alpha outputs will inherit the shadow amount. When the shader is not hit by shadow rays, only the alpha output will inherit the shadow, while the opacity is set to 1.
You will typically connect the color, opacity, and alpha outputs
straight into the
Of, and respectively
Alpha inputs of the Output
It is also possible to disable fog on the surface. To do so, either use
the VEX Matte SHOP in the Shaders module, or create a Parameter VOP, set
its type to "Toggle (
int)", name its parameter "__nofog" (with two
underscores) and enable its Export Parameter option. You do not need
to connect its output to any operator.