1GLSHADEMODEL(3G)                                              GLSHADEMODEL(3G)
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NAME

6       glShadeModel - select flat or smooth shading
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C SPECIFICATION

10       void glShadeModel( GLenum mode )
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PARAMETERS

14       mode  Specifies  a  symbolic  value  representing  a shading technique.
15             Accepted values are GL_FLAT and GL_SMOOTH.  The initial value  is
16             GL_SMOOTH.
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DESCRIPTION

19       GL  primitives can have either flat or smooth shading.  Smooth shading,
20       the default, causes the computed colors of vertices to be  interpolated
21       as the primitive is rasterized, typically assigning different colors to
22       each resulting pixel fragment.  Flat shading selects the computed color
23       of  just one vertex and assigns it to all the pixel fragments generated
24       by rasterizing a single primitive.  In either case, the computed  color
25       of  a vertex is the result of lighting if lighting is enabled, or it is
26       the current color at the time the vertex was specified if  lighting  is
27       disabled.
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29       Flat  and  smooth  shading  are indistinguishable for points.  Starting
30       when glBegin is issued and counting vertices and primitives from 1, the
31       GL  gives  each flat-shaded line segment i the computed color of vertex
32       i+1, its second vertex.  Counting similarly from 1, the GL  gives  each
33       flat-shaded polygon the computed color of the vertex listed in the fol‐
34       lowing table.  This is the last vertex to specify the  polygon  in  all
35       cases  except  single  polygons,  where  the first vertex specifies the
36       flat-shaded color.
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39                        ─────────────────────────────────────
40                        Primitive Type of Polygon i   Vertex
41                        ─────────────────────────────────────
42                        Single polygon (i≡1)            1
43                        Triangle strip                 i+2
44                        Triangle fan                   i+2
45                        Independent triangle            3i
46                        Quad strip                     2i+2
47                        Independent quad                4i
48                        ─────────────────────────────────────
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50       Flat and smooth shading are specified by glShadeModel with mode set  to
51       GL_FLAT and GL_SMOOTH, respectively.
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ERRORS

54       GL_INVALID_ENUM is generated if mode is any value other than GL_FLAT or
55       GL_SMOOTH.
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57       GL_INVALID_OPERATION is generated if glShadeModel is  executed  between
58       the execution of glBegin and the corresponding execution of glEnd.
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ASSOCIATED GETS

61       glGet with argument GL_SHADE_MODEL
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SEE ALSO

64       glBegin(3G), glColor(3G), glLight(3G), glLightModel(3G)
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68                                                              GLSHADEMODEL(3G)
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