glEvalCoord2f(3g)

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

6       glEvalCoord - evaluate enabled one- and two-dimensional maps
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C SPECIFICATION

9       void glEvalCoord1f(GLfloat u);
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11       void glEvalCoord1d(GLdouble u);
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13       void glEvalCoord2f(GLfloat u, GLfloat v);
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15       void glEvalCoord2d(GLdouble u, GLdouble v);
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PARAMETERS

18       u
19           Specifies a value that is the domain coordinate u to the basis
20           function defined in a previous glMap1() or glMap2() command.
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22       v
23           Specifies a value that is the domain coordinate v to the basis
24           function defined in a previous glMap2() command. This argument is
25           not present in a glEvalCoord1 command.
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C SPECIFICATION

28       void glEvalCoord1fv(const GLfloat * u);
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30       void glEvalCoord1dv(const GLdouble * u);
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32       void glEvalCoord2fv(const GLfloat * u);
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34       void glEvalCoord2dv(const GLdouble * u);
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PARAMETERS

37       u
38           Specifies a pointer to an array containing either one or two domain
39           coordinates. The first coordinate is u. The second coordinate is v,
40           which is present only in glEvalCoord2 versions.
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DESCRIPTION

43       glEvalCoord1 evaluates enabled one-dimensional maps at argument u.
44       glEvalCoord2 does the same for two-dimensional maps using two domain
45       values, u and v. To define a map, call glMap1() and glMap2(); to enable
46       and disable it, call glEnable() and glDisable().
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48       When one of the glEvalCoord commands is issued, all currently enabled
49       maps of the indicated dimension are evaluated. Then, for each enabled
50       map, it is as if the corresponding GL command had been issued with the
51       computed value. That is, if GL_MAP1_INDEX or GL_MAP2_INDEX is enabled,
52       a glIndex() command is simulated. If GL_MAP1_COLOR_4 or GL_MAP2_COLOR_4
53       is enabled, a glColor() command is simulated. If GL_MAP1_NORMAL or
54       GL_MAP2_NORMAL is enabled, a normal vector is produced, and if any of
55       GL_MAP1_TEXTURE_COORD_1, GL_MAP1_TEXTURE_COORD_2,
56       GL_MAP1_TEXTURE_COORD_3, GL_MAP1_TEXTURE_COORD_4,
57       GL_MAP2_TEXTURE_COORD_1, GL_MAP2_TEXTURE_COORD_2,
58       GL_MAP2_TEXTURE_COORD_3, or GL_MAP2_TEXTURE_COORD_4 is enabled, then an
59       appropriate glTexCoord() command is simulated.
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61       For color, color index, normal, and texture coordinates the GL uses
62       evaluated values instead of current values for those evaluations that
63       are enabled, and current values otherwise, However, the evaluated
64       values do not update the current values. Thus, if glVertex() commands
65       are interspersed with glEvalCoord commands, the color, normal, and
66       texture coordinates associated with the glVertex() commands are not
67       affected by the values generated by the glEvalCoord commands, but only
68       by the most recent glColor(), glIndex(), glNormal(), and glTexCoord()
69       commands.
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71       No commands are issued for maps that are not enabled. If more than one
72       texture evaluation is enabled for a particular dimension (for example,
73       GL_MAP2_TEXTURE_COORD_1 and GL_MAP2_TEXTURE_COORD_2), then only the
74       evaluation of the map that produces the larger number of coordinates
75       (in this case, GL_MAP2_TEXTURE_COORD_2) is carried out.
76       GL_MAP1_VERTEX_4 overrides GL_MAP1_VERTEX_3, and GL_MAP2_VERTEX_4
77       overrides GL_MAP2_VERTEX_3, in the same manner. If neither a three- nor
78       a four-component vertex map is enabled for the specified dimension, the
79       glEvalCoord command is ignored.
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81       If you have enabled automatic normal generation, by calling glEnable()
82       with argument GL_AUTO_NORMAL, glEvalCoord2 generates surface normals
83       analytically, regardless of the contents or enabling of the
84       GL_MAP2_NORMAL map. Let
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86       m = ∂ p ∂ u × ∂ p ∂ v
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88       Then the generated normal n is n = m m
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90       If automatic normal generation is disabled, the corresponding normal
91       map GL_MAP2_NORMAL, if enabled, is used to produce a normal. If neither
92       automatic normal generation nor a normal map is enabled, no normal is
93       generated for glEvalCoord2 commands.
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ASSOCIATED GETS

96       glIsEnabled() with argument GL_MAP1_VERTEX_3
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98       glIsEnabled() with argument GL_MAP1_VERTEX_4
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100       glIsEnabled() with argument GL_MAP1_INDEX
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102       glIsEnabled() with argument GL_MAP1_COLOR_4
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104       glIsEnabled() with argument GL_MAP1_NORMAL
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106       glIsEnabled() with argument GL_MAP1_TEXTURE_COORD_1
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108       glIsEnabled() with argument GL_MAP1_TEXTURE_COORD_2
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110       glIsEnabled() with argument GL_MAP1_TEXTURE_COORD_3
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112       glIsEnabled() with argument GL_MAP1_TEXTURE_COORD_4
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114       glIsEnabled() with argument GL_MAP2_VERTEX_3
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116       glIsEnabled() with argument GL_MAP2_VERTEX_4
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118       glIsEnabled() with argument GL_MAP2_INDEX
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120       glIsEnabled() with argument GL_MAP2_COLOR_4
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122       glIsEnabled() with argument GL_MAP2_NORMAL
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124       glIsEnabled() with argument GL_MAP2_TEXTURE_COORD_1
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126       glIsEnabled() with argument GL_MAP2_TEXTURE_COORD_2
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128       glIsEnabled() with argument GL_MAP2_TEXTURE_COORD_3
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130       glIsEnabled() with argument GL_MAP2_TEXTURE_COORD_4
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132       glIsEnabled() with argument GL_AUTO_NORMAL
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134       glGetMap()
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COPYRIGHT

142       Copyright © 1991-2006 Silicon Graphics, Inc. This document is licensed
143       under the SGI Free Software B License. For details, see
144       http://oss.sgi.com/projects/FreeB/.
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AUTHORS

147       opengl.org
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151opengl.org                        07/13/2018                   GLEVALCOORD(3G)