glEvalPoint(3G)

NAME
     glEvalPoint1, glEvalPoint2 - generate and evaluate a single point in a
     mesh


C SPECIFICATION
     void glEvalPoint1( GLint i )
     void glEvalPoint2( GLint i,
                        GLint j )


PARAMETERS
     i  Specifies the integer value for grid domain variable i.

     j  Specifies the integer value for grid domain variable j (glEvalPoint2
        only).

DESCRIPTION
     glMapGrid and glEvalMesh are used in tandem to efficiently generate and
     evaluate a series of evenly spaced map domain values.  glEvalPoint can be
     used to evaluate a single grid point in the same gridspace that is
     traversed by glEvalMesh.  Calling glEvalPoint1 is equivalent to calling

                                glEvalCoord1(i*du + u );
                                                     1

                                      where

                                  du = (u -u )/n
                                         2  1


     and n, u , and u  are the arguments to the most recent glMapGrid1
             1       2
     command.  The one absolute numeric requirement is that if i = n, then the
     value computed from i*du + u  is exactly u .
                                 1             2

     In the two-dimensional case, glEvalPoint2, let

                                   du=(u -u )/n
                                        2  1

                                   dv=(v -v )/m
                                        2  1

     where n, u , u , m, v , and v  are the arguments to the most recent
               1   2      1       2
     glMapGrid2 command.  Then the glEvalPoint2 command is equivalent to
     calling

                          glEvalCoord2(i*du + u , j*dv + v );
                                               1          1

     The only absolute numeric requirements are that if i = n, then the value
     computed from i*du + u  is exactly u , and if j = m, then the value
                           1             2
     computed from j*dv + v  is exactly v .
                           1             2
ASSOCIATED GETS
     glGet with argument GL_MAP1_GRID_DOMAIN
     glGet with argument GL_MAP2_GRID_DOMAIN
     glGet with argument GL_MAP1_GRID_SEGMENTS
     glGet with argument GL_MAP2_GRID_SEGMENTS


MACHINE DEPENDENCIES
     RealityEngine, RealityEngine2, and VTX systems do not handle 1D maps for
     colors correctly.


SEE ALSO
     glEvalCoord, glEvalMesh, glMap1, glMap2, glMapGrid