Use GPBISM to insert a Set Back Interior Shading Method structure element into the open structure following the element pointer, or to replace the element pointed at by the element pointer with a Set Back Interior Shading Method element, depending on the current edit mode.
The graPHIGS API uses this element to specify the shading method used for the interior of back facing portions of subsequent area primitives.
This element specifies the way to shade the interior of back facing portions of subsequent area primitives. The specified method is used if the face distinguish mode (GPFDMO) is set to 2=COLOR_SURFACE_PROPERTIES The interior shading methods include 1=SHADING_NONE , which is also known as flat shading, 2=SHADING_COLOR , traditionally known as Gourand shading, and 3=SHADING_DATA See The graPHIGS Programming Interface: Understanding Concepts for information on the interactions between lighting, shading and data mapping.
The traversal default for interior shading method is 2=SHADING_COLOR If the workstation does not support the specified shading method, then the graPHIGS API uses 2=SHADING_COLOR