NAME    [Toc]    [Back]

       glShadeModel - select flat or smooth shading

SYNOPSIS    [Toc]    [Back]

       void glShadeModel(
               GLenum mode );

PARAMETERS    [Toc]    [Back]

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

DESCRIPTION    [Toc]    [Back]

       GL  primitives  can  have  either  flat or smooth shading.
       Smooth shading, the default, causes the computed colors of
       vertices  to  be  interpolated as the primitive is rasterized,
 typically assigning different 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  counting  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 flatshaded
 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           3 i
       Quad strip                    2 i + 2
       Independent quad               4 i
       --------------------------------------

       Flat  and  smooth  shading are specified by glShadeModel()
       with mode set to GL_FLAT and GL_SMOOTH, respectively.

ERRORS    [Toc]    [Back]

       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    [Toc]    [Back]

       glGet() with argument GL_SHADE_MODEL

SEE ALSO    [Toc]    [Back]

       glBegin(3), glColor(3), glLight(3), glLightModel(3)



                                                 glShadeModel(3G)