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# Manual Reference Pages  -  GLEVALPOINT2 (3)

### NAME

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

C Specification
Parameters
Description
Associated Gets

### 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