2008
"Screen" Compositing for Specular and Reflection Elements
The other exception to additive composition is when specular or reflection
elements have been generated by certain material shaders. These shaders
generate specular and reflection elements you must composite differently:
■ Anisotropic
■ Multi-Layer
■ Oren-Nayar-Blinn
Shaders are assigned on a per-material basis, in the Material Editor. If you
render specular or reflection elements in a scene that uses these shaders, then
composite them with the diffuse and other foreground components (aside
from colored shadows, as described above), by overlaying them using an
operation called "Screen" in some compositing programs.
Screen compositing uses this formula to combine elements:
Background * (1 - Foreground) + Foreground
The background is multiplied by the inverse of the foreground color, and then
the foreground color is added to the result.
For more information, see the documentation for the compositing program
you use.
Procedures
To have the Render Elements dialog assign names to the rendered element
files automatically:
1 In the Render Scene dialog's Common Parameters rollout, use the Files
button to assign an output file name and file type for the (entire) rendered
scene.
2 In the Render Elements rollout, use the Add button to add elements for
rendering.
You can render elements to files without rendering the entire scene to a file,
but in this case, you have to assign the files for the elements individually or
"by hand."
To add an element for rendering:
1 Click Add.
Render Elements Panel and Rollout | 6151