glShadeModel

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 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 com-
       puted  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  speci-
       fied 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 flat-shaded polygon the computed color of the vertex listed
       in the following table.	This is the last vertex to specify the	poly-
       gon in all cases except single polygons, where the first vertex speci-
       fies 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, respectively.

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)