# glEvalPoint.3G man page

glEvalPoint — 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
⋅
Δ
u
+
u
1
);
```

where Δ u = u 2 - u 1 n

and n, u 1, and u 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 ⋅ Δ u + u 1 is exactly u 2.

In the two-dimensional case, **glEvalPoint2**, let

Δ u = u 2 - u 1 n.PP Δ v = v 2 - v 1 m

where n, u 1, u 2, m, v 1, and v 2 are the arguments to the most recent **glMapGrid2**() command. Then the **glEvalPoint2** command is equivalent to calling

```
glEvalCoord2(
i
⋅
Δ
u
+
u
1
,
j
⋅
Δ
v
+
v
1
);
```

The only absolute numeric requirements are that if i = n, then the value computed from i ⋅ Δ u + u 1 is exactly u 2, and if j = m, then the value computed from j ⋅ Δ v + v 1 is exactly v 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**()

## Copyright

Copyright © 1991-2006 Silicon Graphics, Inc. This document is licensed under the SGI Free Software B License. For details, see http://oss.sgi.com/projects/FreeB/.

## Authors

**opengl.org**

## Referenced By

glEvalPoint1.3G(3) and glEvalPoint2.3G(3) are aliases of glEvalPoint.3G(3).