OpenGL man pages

```

```

## 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·du + u );
1
where

du = (u	-u )/n
2  1

and n, u , and u  are	the arguments to the most recent glMapGrid1 command.
1       2
The one absolute numeric requirement is that if i = n, then the value
computed from	i·du + u  is exactly u .
1	      2

In the two-dimensional case, glEvalPoint2, let

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

glEvalCoord2(i·du	+ u , j·dv + v );
1          1

The only absolute numeric requirements are that if i = n, then the value
computed from	i·du + u  is exactly u , and if	j = m, then the	value
1             2
computed from	j·dv + 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

```

```  glEvalCoord, glEvalMesh, glMap1, glMap2, glMapGrid