DragonFly On-Line Manual Pages

GLEVALPOINT()                                                    GLEVALPOINT()

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 . DELTA u + u );
                                   1
       where

       DELTA u = (u - u  ) / n
                   2   1

       and n, u , and u
               1       2

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

       In the two-dimensional case, glEvalPoint2, let
       DELTA u = (u  - u )/n
                   2    1

       DELTA v = (v  - v )/m
                   2    1

       where n, u , u , m, v , and v
                 1   2      1       2

       are the arguments to the most recent glMapGrid2 command.  Then the
       glEvalPoint2 command is equivalent to calling

       glEvalCoord2(i .  DELTA u + u , j . DELTA v + v );
                                    1                 1

       The only absolute numeric requirements are that if i = n, then the
       value computed from

       i . DELTA u + u  is exactly u ,
                      1             2
       and if j = m, then the value computed from

       j cdot DELTA v + 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

SEE ALSO
       glEvalCoord, glEvalMesh, glMap1, glMap2, glMapGrid

                                                                 GLEVALPOINT()