glShadeModel(3G)	       OpenGL Reference		      glShadeModel(3G)

NAME    [Toc]    [Back]

     glShadeModel - select flat	or smooth shading

C SPECIFICATION    [Toc]    [Back]

     void glShadeModel(	GLenum mode )

PARAMETERS    [Toc]    [Back]

     mode  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	       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    [Toc]    [Back]

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





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glShadeModel(3G)	       OpenGL Reference		      glShadeModel(3G)



     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, glColor, glLight,	glLightModel


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