1991-2006 Silicon Graphics, Inc.
glMapGrid 3G
glMapGrid define a one- or two-dimensional mesh

## C Specification

void `glMapGrid1d` GLint un GLdouble u1 GLdouble u2 void `glMapGrid1f` GLint un GLfloat u1 GLfloat u2 void `glMapGrid2d` GLint un GLdouble u1 GLdouble u2 GLint vn GLdouble v1 GLdouble v2 void `glMapGrid2f` GLint un GLfloat u1 GLfloat u2 GLint vn GLfloat v1 GLfloat v2

## Parameters

un

  Specifies the number of partitions in the grid range interval [u1, u2]. Must be positive.

u1
u2

  Specify the mappings for integer grid domain values i = 0 and i = un .

vn

  Specifies the number of partitions in the grid range interval [v1, v2] (`glMapGrid2` only).

v1
v2

  Specify the mappings for integer grid domain values j = 0 and j = vn (`glMapGrid2` only).

## Description

`glMapGrid` and glEvalMesh are used together to efficiently generate and evaluate a series of evenly-spaced map domain values. glEvalMesh 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.

`glMapGrid1` and `glMapGrid2` 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.

`glMapGrid1` 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 so that

u = i ⁡ u2 - u1 un + u1

`glMapGrid2` 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.

## Errors

`GL_INVALID_VALUE` is generated if either un or vn is not positive.

`GL_INVALID_OPERATION` is generated if `glMapGrid` is executed between the execution of glBegin and the corresponding execution of glEnd.

## 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, glEvalPoint, glMap1, glMap2

## 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/.