The RenderMan Interface - Paul Bourke

SEE ALSO
RiGeometricApproximation
4.2.8 Shading interpolation
Shading calculations are performed at discrete positions on surface elements or in screen
space (at a frequency determined by the shading rate). The results can then either be interpolated
or constant over some region of the screen or the interior of a surface element
corresponding to one shading sample. This is controlled by the following procedure:
RiShadingInterpolation ( RtToken type )
This function controls how values are interpolated between shading samples (usually
across a polygon or over an area of the screen). If type is ”constant”, the color and
opacity of all the pixels inside the region are the same. This is often referred to as flat
or faceted shading. If type is ”smooth”, the color and opacity of all the pixels between
shaded values are interpolated from the calculated values. This is often referred to as
Gouraud shading.
RIB BINDING
ShadingInterpolation ”constant”
ShadingInterpolation ”smooth”
EXAMPLE
ShadingInterpolation ”smooth”
4.2.9 Matte objects
Matte objects are the functional equivalent of three-dimensional hold-out mattes. Matte
objects are not shaded and are set to be completely opaque so that they hide objects behind
them. However, regions in the output image where a matte object is visible are treated as
transparent.
RiMatte ( RtBoolean onoff )
Indicates whether subsequent primitives are matte objects.
RIB BINDING
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