MSDN Library

# glEvalPoint1, glEvalPoint2

The glEvalPoint1 and glEvalPoint2 functions generate and evaluate a single point in a mesh.

```void glEvalPoint1(
GLint i
);

void glEvalPoint2(
GLint i,
GLint j
);
```

#### Parameters

i
The integer value for grid domain variable i.
j
The integer value for grid domain variable j (glEvalPoint2 only).

#### Remarks

The glMapGrid and glEvalMesh functions are used in tandem to efficiently generate and evaluate a series of evenly spaced map domain values. You can use glEvalPoint 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 + u1);

where

&Delta;u = (u2 u1) / n

and n, u1, and u2 are the arguments to the most recent glMapGrid1 function. The one absolute numeric requirement is that if i = n, then the value computed from i&Delta; u + u1 is exactly u2.

In the two-dimensional case, glEvalPoint2, let

&Delta;u = (u2 u1)/n

&Delta;v = (v2 v1)/m

where n, u1, u2, m, v1, and v2 are the arguments to the most recent glMapGrid2 function. Then the glEvalPoint2 function is equivalent to calling

glEvalCoord2(i&Delta;u + u1, j&Delta;v + v1);

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

The following functions retrieve information relating to glEvalPoint1 and glEvalPoint2:

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

#### Requirements

Windows NT/2000: Requires Windows NT 3.5 or later.
Windows 95/98: Requires Windows 95 or later. Available as a redistributable for Windows 95.