# glMapGrid1f function

Applies to: desktop apps only

Defines a one-dimensional mesh.

### Syntax

```void WINAPI glMapGrid1f(
GLint un,
GLfloat u1,
GLfloat u2
);
```

### Parameters

un

The number of partitions in the grid range interval [u1, u2]. This value must be positive.

u1

A value used as the mapping for integer grid domain value i = 0.

u2

A value used as the mapping for integer grid domain value i = un.

### Return value

This function does not return a value.

### Error codes

The following error codes can be retrieved by the glGetError function.

NameMeaning
GL_INVALID_VALUE

Either un or vn was not positive.

GL_INVALID_OPERATION

The function was called between a call to glBegin and the corresponding call to glEnd.

### Remarks

The glMapGrid and glEvalMesh functions are used in tandem to efficiently generate and evaluate a series of evenly spaced map domain values. The glEvalMesh function steps through the integer domain of a one- or two-dimensional grid, whose range is the domain of the evaluation maps specified by glMap1 and glMap2.

The glMapGrid1 and glMapGrid2 functions specify the linear grid mappings between the i (or i and j) integer grid coordinates, to the u (or u and v) floating-point evaluation map coordinates. See glMap1 and glMap2 for details of how u and v coordinates are evaluated.

The glMapGrid1 function specifies a single linear mapping such that integer grid coordinate 0 maps exactly to u1, and integer grid coordinate un maps exactly to u2. All other integer grid coordinates i are mapped such that:

u = i(u2 u1)/un + u1

The glMapGrid2 function specifies two such linear mappings. One maps integer grid coordinate i = 0 exactly to u1, and integer grid coordinate i = un exactly to u2. The other maps integer grid coordinate j = 0 exactly to v1, and integer grid coordinate j = vn exactly to v2. Other integer grid coordinates i and j are mapped such that

u = i(u2 u1)/un + u1

v = j (v2 v1)/vn + v1

The mappings specified by glMapGrid are used identically by glEvalMesh and glEvalPoint.

The following functions retrieve information related to glMapGrid:

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

 Minimum supported client Windows 2000 Professional Windows 2000 Server Gl.h Opengl32.lib Opengl32.dll

glBegin
glEnd
glEvalCoord
glEvalMesh
glEvalPoint
glMap1
glMap2