**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**