GLSHADEMODEL(3G) UNIX Programmer's Manual 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 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 seg-
ment i the computed color of vertex i + 1, its second ver-
tex. 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.
MirBSD #10-current Printed 2021-12-07 1
GLSHADEMODEL(3G) UNIX Programmer's Manual GLSHADEMODEL(3G)
GL_INVALID_OPERATION is generated if glShadeModel is exe-
cuted 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)
MirBSD #10-current Printed 2021-12-07 2