GLEVALCOORD(3G) GLEVALCOORD(3G)

glEvalCoord1d, glEvalCoord1f, glEvalCoord2d, glEvalCoord2f, glEvalCoord1dv, glEvalCoord1fv, glEvalCoord2dv, glEvalCoord2fv - evaluate enabled one- and two-dimensional maps

C SPECIFICATION

void glEvalCoord1d( GLdouble u )



void glEvalCoord1f( GLfloat u )




void glEvalCoord2d( GLdouble u,


	GLdouble v )


void glEvalCoord2f( GLfloat u,


	GLfloat v )











  

  
Specifies a value that is the domain coordinate u to the basis function
      defined in a previous glMap1 or glMap2 command.

  

  
Specifies a value that is the domain coordinate v to the basis function
      defined in a previous glMap2 command. This argument is not present
      in a glEvalCoord1 command.








C SPECIFICATION


void glEvalCoord1dv( const GLdouble *u )




void glEvalCoord1fv( const GLfloat *u )




void glEvalCoord2dv( const GLdouble *u )




void glEvalCoord2fv( const GLfloat *u )













  

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










glEvalCoord1 evaluates enabled one-dimensional maps at
    argument u. glEvalCoord2 does the same for two-dimensional
    maps using two domain values, u and v. To define a map, call
    glMap1 and glMap2; to enable and disable it, call
    glEnable and glDisable.


When one of the glEvalCoord commands is issued, all
    currently enabled maps of the indicated dimension are evaluated. Then, for
    each enabled map, it is as if the corresponding GL command had been issued
    with the computed value. That is, if GL_MAP1_INDEX or
    GL_MAP2_INDEX is enabled, a glIndex command is simulated. If
    GL_MAP1_COLOR_4 or GL_MAP2_COLOR_4 is enabled, a
    glColor command is simulated. If GL_MAP1_NORMAL or
    GL_MAP2_NORMAL is enabled, a normal vector is produced, and if any of
    GL_MAP1_TEXTURE_COORD_1, GL_MAP1_TEXTURE_COORD_2,
    GL_MAP1_TEXTURE_COORD_3, GL_MAP1_TEXTURE_COORD_4,
    GL_MAP2_TEXTURE_COORD_1, GL_MAP2_TEXTURE_COORD_2,
    GL_MAP2_TEXTURE_COORD_3, or GL_MAP2_TEXTURE_COORD_4 is
    enabled, then an appropriate glTexCoord command is simulated.


For color, color index, normal, and texture coordinates the GL
    uses evaluated values instead of current values for those evaluations that
    are enabled, and current values otherwise, However, the evaluated values do
    not update the current values. Thus, if glVertex commands are
    interspersed with glEvalCoord commands, the color, normal, and
    texture coordinates associated with the glVertex commands are not
    affected by the values generated by the glEvalCoord commands, but
    only by the most recent glColor, glIndex, glNormal, and
    glTexCoord commands.


No commands are issued for maps that are not enabled. If more than
    one texture evaluation is enabled for a particular dimension (for example,
    GL_MAP2_TEXTURE_COORD_1 and GL_MAP2_TEXTURE_COORD_2), then
    only the evaluation of the map that produces the larger number of
    coordinates (in this case, GL_MAP2_TEXTURE_COORD_2) is carried out.
    GL_MAP1_VERTEX_4 overrides GL_MAP1_VERTEX_3, and
    GL_MAP2_VERTEX_4 overrides GL_MAP2_VERTEX_3, in the same
    manner. If neither a three- nor a four-component vertex map is enabled for
    the specified dimension, the glEvalCoord command is ignored.


If you have enabled automatic normal generation, by calling
    glEnable with argument GL_AUTO_NORMAL, glEvalCoord2
    generates surface normals analytically, regardless of the contents or
    enabling of the GL_MAP2_NORMAL map. Let



  

  m = (partial (p) / partial (u)) X (partial (p) over partial (v))
  

  




Then the generated normal n is
  

  

   n = m / { || m || }
  

  




If automatic normal generation is disabled, the corresponding
    normal map GL_MAP2_NORMAL, if enabled, is used to produce a normal.
    If neither automatic normal generation nor a normal map is enabled, no
    normal is generated for glEvalCoord2 commands.








glIsEnabled with argument GL_MAP1_VERTEX_3


glIsEnabled with argument GL_MAP1_VERTEX_4


glIsEnabled with argument GL_MAP1_INDEX


glIsEnabled with argument GL_MAP1_COLOR_4


glIsEnabled with argument GL_MAP1_NORMAL


glIsEnabled with argument GL_MAP1_TEXTURE_COORD_1


glIsEnabled with argument GL_MAP1_TEXTURE_COORD_2


glIsEnabled with argument GL_MAP1_TEXTURE_COORD_3


glIsEnabled with argument GL_MAP1_TEXTURE_COORD_4


glIsEnabled with argument GL_MAP2_VERTEX_3


glIsEnabled with argument GL_MAP2_VERTEX_4


glIsEnabled with argument GL_MAP2_INDEX


glIsEnabled with argument GL_MAP2_COLOR_4


glIsEnabled with argument GL_MAP2_NORMAL


glIsEnabled with argument GL_MAP2_TEXTURE_COORD_1


glIsEnabled with argument GL_MAP2_TEXTURE_COORD_2


glIsEnabled with argument GL_MAP2_TEXTURE_COORD_3


glIsEnabled with argument GL_MAP2_TEXTURE_COORD_4


glIsEnabled with argument GL_AUTO_NORMAL


glGetMap








glBegin, glColor, glEnable,
    glEvalMesh, glEvalPoint, glIndex, glMap1,
    glMap2, glMapGrid, glNormal, glTexCoord,
    glVertex