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GLSHADEMODEL(3G)                                                                            GLSHADEMODEL(3G)



NAME
       glShadeModel - select flat or smooth shading


C SPECIFICATION
       void glShadeModel( GLenum mode )


PARAMETERS
       mode  Specifies  a  symbolic value representing a shading technique.  Accepted values are GL_FLAT and
             GL_SMOOTH.  The initial value is GL_SMOOTH.

DESCRIPTION
       GL primitives can have either flat or smooth shading.  Smooth shading, the default, causes  the  com-puted computed
       puted  colors of vertices to be interpolated as the primitive is rasterized, typically assigning dif-ferent different
       ferent colors to each resulting pixel fragment.  Flat shading selects the computed color of just  one
       vertex  and  assigns  it  to all the pixel fragments generated by rasterizing a single primitive.  In
       either case, the computed color of a vertex is the result of lighting if lighting is enabled,  or  it
       is the current color at the time the vertex was specified if lighting is disabled.

       Flat and smooth shading are indistinguishable for points.  Starting when glBegin is issued and count-ing counting
       ing vertices and primitives from 1, the GL gives each flat-shaded line segment i the  computed  color
       of vertex i + 1, its second vertex.  Counting similarly from 1, the GL gives each flat-shaded polygon
       the computed color of the vertex listed in the following table.  This is the last vertex  to  specify
       the  polygon  in  all  cases except single polygons, where the first vertex specifies the flat-shaded
       color.

              Primitive Type of Polygon i       Vertex
              Single polygon ( i == 1)             1
              Triangle strip                    i + 2
              Triangle fan                      i + 2
              Independent triangle                3i
              Quad strip                        2i + 2
              Independent quad               4i

       Flat and smooth shading are specified by glShadeModel with mode set to GL_FLAT and GL_SMOOTH, respec-tively. respectively.
       tively.

ERRORS
       GL_INVALID_ENUM is generated if mode is any value other than GL_FLAT or GL_SMOOTH.

       GL_INVALID_OPERATION  is  generated  if glShadeModel is executed between the execution of glBegin and
       the corresponding execution of glEnd.

ASSOCIATED GETS
       glGet with argument GL_SHADE_MODEL

SEE ALSO
       glBegin(3G), glColor(3G), glLight(3G), glLightModel(3G)




                                                                                            GLSHADEMODEL(3G)