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  interpo-
       lated as the primitive is rasterized, typically assigning different colors to each resulting pixel fragment.  Flat shading selects the com-
       puted 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 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 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, 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, glColor, glLight, glLightModel

																  GLSHADEMODEL(3G)