GLSHADEMODEL

Index

NAME

glShadeModel - select flat or smooth shading

C SPECIFICATION

void f3glShadeModelfP( GLenum fImodefP )

delim $$

PARAMETERS

f2modefP: Specifies a symbolic value representing a shading technique. Accepted values are %f3GL_FLATfP and %f3GL_SMOOTHfP. The initial value is %f3GL_SMOOTHfP.

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 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 %f3glBeginfP 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	$ 3 i$
Quad strip	$2 i ~+~ 2$
Independent quad	$ 4 i $

Flat and smooth shading are specified by %f3glShadeModelfP with f2modefP set to %f3GL_FLATfP and %f3GL_SMOOTHfP, respectively.

ERRORS

%f3GL_INVALID_ENUMfP is generated if f2modefP is any value other than %f3GL_FLATfP or %f3GL_SMOOTHfP. %f3GL_INVALID_OPERATIONfP is generated if %f3glShadeModelfP is executed between the execution of %f3glBeginfP and the corresponding execution of %f3glEndfP.

ASSOCIATED GETS

%f3glGetfP with argument %f3GL_SHADE_MODELfP

GLSHADEMODEL

NAME

C SPECIFICATION

PARAMETERS

DESCRIPTION

ERRORS

ASSOCIATED GETS

SEE ALSO

Index