NAME
          DtShapeGetPolygonNormal - Get a polygon normal for the given shape and
          normal index.


     SYNOPSIS
          #include <Dt.h>


          int  DtShapeGetPolygonNormal( int shapeID, int index, DtVec3f *normal )


     DESCRIPTION
          DtShapeGetPolygonNormal() returns a polygon normal for the shape indicated
          by the given shapeID and index. The noraml is returned via
          the pointer to the vertex parameter.  C programmers can
          access the components of the vertex vector as though it were
          a simple structure as follows:

                    typedef struct DtVec3f { float vec[3];};

                    DtVec3f norm;
                    x = norm.vec[0];
                    y = norm.vec[1];
                    z = norm.vec[2];

          This is for flat shaded polygons

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


     FILES
          Link with -lDtOMio