glEvalCoord2f(3g)

1GLEVALCOORD(3G)                                                GLEVALCOORD(3G)
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NAME

6       glEvalCoord1d,  glEvalCoord1f,  glEvalCoord2d, glEvalCoord2f, glEvalCo‐
7       ord1dv,  glEvalCoord1fv,  glEvalCoord2dv,  glEvalCoord2fv  -   evaluate
8       enabled one- and two-dimensional maps
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C SPECIFICATION

12       void glEvalCoord1d( GLdouble u )
13       void glEvalCoord1f( GLfloat u )
14       void glEvalCoord2d( GLdouble u,
15                           GLdouble v )
16       void glEvalCoord2f( GLfloat u,
17                           GLfloat v )
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PARAMETERS

21       u  Specifies a value that is the domain coordinate u to the basis func‐
22          tion defined in a previous glMap1 or glMap2 command.
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24       v  Specifies a value that is the domain coordinate v to the basis func‐
25          tion  defined  in  a  previous glMap2 command.  This argument is not
26          present in a glEvalCoord1 command.
27

C SPECIFICATION

29       void glEvalCoord1dv( const GLdouble *u )
30       void glEvalCoord1fv( const GLfloat *u )
31       void glEvalCoord2dv( const GLdouble *u )
32       void glEvalCoord2fv( const GLfloat *u )
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34

PARAMETERS

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

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

94       glIsEnabled with argument GL_MAP1_VERTEX_3
95       glIsEnabled with argument GL_MAP1_VERTEX_4
96       glIsEnabled with argument GL_MAP1_INDEX
97       glIsEnabled with argument GL_MAP1_COLOR_4
98       glIsEnabled with argument GL_MAP1_NORMAL
99       glIsEnabled with argument GL_MAP1_TEXTURE_COORD_1
100       glIsEnabled with argument GL_MAP1_TEXTURE_COORD_2
101       glIsEnabled with argument GL_MAP1_TEXTURE_COORD_3
102       glIsEnabled with argument GL_MAP1_TEXTURE_COORD_4
103       glIsEnabled with argument GL_MAP2_VERTEX_3
104       glIsEnabled with argument GL_MAP2_VERTEX_4
105       glIsEnabled with argument GL_MAP2_INDEX
106       glIsEnabled with argument GL_MAP2_COLOR_4
107       glIsEnabled with argument GL_MAP2_NORMAL
108       glIsEnabled with argument GL_MAP2_TEXTURE_COORD_1
109       glIsEnabled with argument GL_MAP2_TEXTURE_COORD_2
110       glIsEnabled with argument GL_MAP2_TEXTURE_COORD_3
111       glIsEnabled with argument GL_MAP2_TEXTURE_COORD_4
112       glIsEnabled with argument GL_AUTO_NORMAL
113       glGetMap
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