NAME
          DtFaceGetMaterialIndex - Gets the list of polygonal material
          indices for all the polygons in the given shape and group
          IDs.


     SYNOPSIS
          #include <Dt.h>


          int  DtFaceGetMaterialIndex( int shapeID, int groupID, int *count, long **indices);


     DESCRIPTION
          DtFaceGetMaterialIndex() returns a list of polygon material
          indices via the pointer to the variable indices given the
          shape number, shapeID, and group number, groupID. The total
          number of material indices into the material list (the
          length of the indices array) is returned via the pointer to
          the count parameter.  Each polygon in the indices array is
          separated by an index DtEND_OF_FACE (-1). The number of
          indices return via the pointer to count includes the
          DtEND_OF_FACE separators.  For example, if the first group
          (groupID = 0) of the first shape (shapeID = 0) has two
          triangles, the format of the material index array will be:

               1 2 3 -1 4 5 6 -1

          were indices 1, 2, and 3 are for polygon 0 and 4, 5, and 6
          are for polygon 1.  The parameter count will be set to 8.

          If the face does not contain material indices for materials
          indices array will be set to NULL. This occurs when the
          entire face is a single material.  The indices array is an
          internal buffer.  Do not free or modify the index array.


     IMPLEMENTATION NOTES
          The AliasAPI implementation of Dt does not implement faces
          containing multiple materials.  DtFaceGetMaterialIndex()
          will return a count of zero and a NULL array of indices.
          Per-vertex coloring is achieved using the
          DtShapeGetVerticesColor(3W) function.


     DIAGNOSTICS
          DtFaceGetMaterialIndex() returns one on success and zero on
          failure.


     SEE ALSO
          DtIndexCount(3W)
     FILES
          Link with -lDtOMio