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 variablei.

j Specifies the integer value for grid domain variablej (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 ifi = 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 ifi = n, then the value computed from

i . DELTA u + u is exactly u ,
1 2

and ifj = 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