- evaluate enabled one- and two-dimensional maps



C SPECIFICATION


PARAMETERS

       _param1  Specifies a value that is the domain coordinate u
                to the  basis  function  defined  in  a  previous
                glMap1 or glMap2 command.

       _param2  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


PARAMETERS

       _param1
              Specifies a pointer to an array  containing  either
              one  or  two domain coordinates.  The first coordi-
              nate is u.  The second coordinate is  v,  which  is
              present only in glEvalCoord2 versions.


DESCRIPTION

       glEvalCoord1  evaluates  enabled  one-dimensional  maps at
       argument _param1(1).  glEvalCoord2 does the same for  two-
       dimensional  maps  using two domain values, _param1(1) and
       _param2(1).  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 cur-
       rently enabled maps of the indicated dimension are  evalu-
       ated.   Then, for each enabled map, it is as if the corre-
       sponding 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  simu-
       lated.

       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 inter-
       spersed with glEvalCoord commands, the color, normal,  and
       texture  coordinates associated with the glVertex commands
       glEvalCoord command is ignored.

       If you have enabled automatic normal generation, by  call-
       ing  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=_<I>u_x_<I>v_

       Then the generated normal n is
                                n=_____

       If  automatic  normal  generation  is disabled, the corre-
       sponding 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.


ASSOCIATED GETS

       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


SEE ALSO

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



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