Auxiliary Bitplane Control
The framebuffer always contains a color bitplane and a depth bitplane. It may also have a stencil bitplane or accumulation bitplane. In addition, if it is a render-to-texture framebuffer, it may have auxiliary bitplanes. These allow more or less arbitrary user-defined data to be stored along with each pixel in the framebuffer, alongside its color and depth value.
The main use case for this is to pass along additional information to a postprocessing shader, which operates on the pixels of the rendered image. For example, the cartoon inking shader needs to have the normal vector of every rendered pixel in order to determine where the edges of the objects are.
bits is a set of bits indicating what should be written into the
Although the framebuffer’s alpha channel is not technically an auxiliary bitplane, it can be thought of as such, since it is not generally used to store any data of value, since alpha blending has already occurred before the values are written to the framebuffer.
When the shader generator is not enabled, this attrib has no effect.
Values That Can be Requested
The following is a list of bits that can be passed to
Copy the glow map (aka self-illumination map) into the alpha channel of the framebuffer. Usually this is a prelude to running a bloom filter over the scene.
Store the camera-space normal of the polygon surface in the RGB channels of the first auxiliary bitplane. This is often used to help detect edges in a cartoon inking filter.
Copy the glow map (aka self-illumination map) into the alpha channel of the first auxiliary bitplane.