- generate and evaluate a single point in a mesh



C SPECIFICATION


PARAMETERS

       _param1  Specifies the integer value for grid domain vari-
                able i.

       _param2  Specifies the integer value for grid domain vari-
                able 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./\u+u1 );

where

              /\u=(u2-u1)/n



and n, u1, and u2 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./\u+u1 is exactly u2.


In the two-dimensional case, glEvalPoint2, let


       /\u=(u2-u1)/n

       /\v=(v2-v1)/m,

where n, u1, u2, m, v1, and v2 are  the  arguments  to  the  most

recent glMapGrid2 command. Then the glEvalPoint2 command is

equivalent to calling


       glEvalCoord2( i./\u+u1, j./\v+v1 );

The only absolute numeric requirements are that if i=n, then  the
value  computed from i./\u+u1 is exactly u2, and if j=m, then the
value computed from i./\v+v1 is exactly v2.


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