GLEVALCORD(3G)                                                GLEVALCORD(3G)



NAME
       glEvalCoord1d,,  glEvalCoord1f,,  glEvalCoord2d,, glEvalCoord2f,, glEvalCo-
       ord1dv,,  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 )


PARAMETERS
       u  Specifies a value that is the domain coordinate u to the basis func-
          tion defined in a previous glap1 or glap2 command.

       v  Specifies a value that is the domain coordinate v to the basis func-
          tion  defined  in  a  previous glap2 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 )


PARAMETERS
       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.

DESCRIPTION
       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 glap1 and glap2; 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 GLMAP1INDEX or GLMAP2INDEX is enabled,
       a glIndex command is simulated.  If GLMAP1COLOR4 or  GLMAP2COLOR4
       is  enabled,  a  glColor  command  is  simulated.  If GLMAP1NORMAL or
       GLMAP2NORMAL is enabled, a normal vector is produced, and if  any  of
       GLMAP1TEXTURECORD1,                       GLMAP1TEXTURECORD2,
       GLMAP1TEXTURECORD3,                       GLMAP1TEXTURECORD4,
       GLMAP2TEXTURECORD1,                       GLMAP2TEXTURECORD2,
       GLMAP2TEXTURECORD3, or GLMAP2TEXTURECORD4 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 val-
       ues 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,
       GLMAP2TEXTURECORD1 and  GLMAP2TEXTURECORD2),  then  only  the
       evaluation  of  the  map that produces the larger number of coordinates
       (in   this   case,    GLMAP2TEXTURECORD2)    is    carried    out.
       GLMAP1VERTEX4 overrides GLMAP1VERTEX3, and GLMAP2VERTEX4 over-
       rides GLMAP2VERTEX3, 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  GLAUTONORMAL,  glEvalCoord2 generates surface normals
       analytically,  regardless  of  the  contents   or   enabling   of   the
       GLMAP2NORMAL map.  Let

                                     m=ap/auX

       Then the generated normal n  is
                                 n = m / {  m  }

       If  automatic  normal  generation is disabled, the corresponding normal
       map GLMAP2NORMAL, if enabled, is used to produce a normal.   If  nei-
       ther automatic normal generation nor a normal map is enabled, no normal
       is generated for glEvalCoord2 commands.

ASOCIATED GETS
       glIsEnabled with argument GLMAP1VERTEX3
       glIsEnabled with argument GLMAP1VERTEX4
       glIsEnabled with argument GLMAP1INDEX
       glIsEnabled with argument GLMAP1COLOR4
       glIsEnabled with argument GLMAP1NORMAL
       glIsEnabled with argument GLMAP1TEXTURECORD1
       glIsEnabled with argument GLMAP1TEXTURECORD2
       glIsEnabled with argument GLMAP1TEXTURECORD3
       glIsEnabled with argument GLMAP1TEXTURECORD4
       glIsEnabled with argument GLMAP2VERTEX3
       glIsEnabled with argument GLMAP2VERTEX4
       glIsEnabled with argument GLMAP2INDEX
       glIsEnabled with argument GLMAP2COLOR4
       glIsEnabled with argument GLMAP2NORMAL
       glIsEnabled with argument GLMAP2TEXTURECORD1
       glIsEnabled with argument GLMAP2TEXTURECORD2
       glIsEnabled with argument GLMAP2TEXTURECORD3
       glIsEnabled with argument GLMAP2TEXTURECORD4
       glIsEnabled with argument GLAUTONORMAL
       glGetap

SEE ALSO
       glBegin, glColor, glEnable, glEvalesh, glEvalPoint,  glIndex,  glap1,
       glap2, glapGrid, glNormal, glTexCoord, glVertex



                                                               GLEVALCORD(3G)