1GLSHADEMODEL(3G)                 OpenGL Manual                GLSHADEMODEL(3G)
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NAME

6       glShadeModel - select flat or smooth shading
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C SPECIFICATION

9       void glShadeModel(GLenum mode);
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PARAMETERS

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

18       GL primitives can have either flat or smooth shading. Smooth shading,
19       the default, causes the computed colors of vertices to be interpolated
20       as the primitive is rasterized, typically assigning different colors to
21       each resulting pixel fragment. Flat shading selects the computed color
22       of just one vertex and assigns it to all the pixel fragments generated
23       by rasterizing a single primitive. In either case, the computed color
24       of a vertex is the result of lighting if lighting is enabled, or it is
25       the current color at the time the vertex was specified if lighting is
26       disabled.
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28       Flat and smooth shading are indistinguishable for points. Starting when
29       glBegin() is issued and counting vertices and primitives from 1, the GL
30       gives each flat-shaded line segment i the computed color of vertex i +
31       1, its second vertex. Counting similarly from 1, the GL gives each
32       flat-shaded polygon the computed color of the vertex listed in the
33       following table. This is the last vertex to specify the polygon in all
34       cases except single polygons, where the first vertex specifies the
35       flat-shaded color.
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37       ┌───────────────────────────────────┬───────────────────────────────────┐
38       │                                   │                                   │
39Primitive  Vertex   
40Type of Polygon                    │                                   │
41i          │                                   │
42       │                                   │                                   │
43       ├───────────────────────────────────┼───────────────────────────────────┤
44       │Single polygon                     │                 1                 │
45       │                        (          │                                   │
46       │                                   │                                   │
47       │                                   │                                   │
48       │                                i  │                                   │
49       │                                == │                                   │
50       │                                1  │                                   │
51       │                                   │                                   │
52       │                        )          │                                   │
53       ├───────────────────────────────────┼───────────────────────────────────┤
54       │Triangle strip                     │ i                                 │
55       │                                   │                                 + │
56       │                                   │                                 2 │
57       ├───────────────────────────────────┼───────────────────────────────────┤
58       │Triangle fan                       │ i                                 │
59       │                                   │                                 + │
60       │                                   │                                 2 │
61       ├───────────────────────────────────┼───────────────────────────────────┤
62       │Independent triangle               │ 3                                 │
63       │                                   │                                 ⁢ │
64       │                                   │                                 i │
65       ├───────────────────────────────────┼───────────────────────────────────┤
66       │Quad strip                         │ 2                                 │
67       │                                   │                                 ⁢ │
68       │                                   │                                 i │
69       │                                   │                                 + │
70       │                                   │                                 2 │
71       ├───────────────────────────────────┼───────────────────────────────────┤
72       │Independent quad                   │ 4                                 │
73       │                                   │                                 ⁢ │
74       │                                   │                                 i │
75       └───────────────────────────────────┴───────────────────────────────────┘
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77       Flat and smooth shading are specified by glShadeModel with mode set to
78       GL_FLAT and GL_SMOOTH, respectively.
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ERRORS

81       GL_INVALID_ENUM is generated if mode is any value other than GL_FLAT or
82       GL_SMOOTH.
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84       GL_INVALID_OPERATION is generated if glShadeModel is executed between
85       the execution of glBegin() and the corresponding execution of glEnd().
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ASSOCIATED GETS

88       glGet() with argument GL_SHADE_MODEL
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SEE ALSO

91       glBegin(), glColor(), glLight(), glLightModel()
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94       Copyright © 1991-2006 Silicon Graphics, Inc. This document is licensed
95       under the SGI Free Software B License. For details, see
96       http://oss.sgi.com/projects/FreeB/.
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AUTHORS

99       opengl.org
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103opengl.org                        07/13/2018                  GLSHADEMODEL(3G)
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