1991-2006
Silicon Graphics, Inc.
gluBuild2DMipmapLevels
3G

# gluBuild2DMipmapLevels

builds a subset of two-dimensional mipmap levels

## C Specification

                    GLint gluBuild2DMipmapLevels
                    GLenum target
                    GLint internalFormat
                    GLsizei width
                    GLsizei height
                    GLenum format
                    GLenum type
                    GLint level
                    GLint base
                    GLint max
                    const void * data

## Parameters

`target`

  Specifies the target texture. Must be `GLU_TEXTURE_2D`.

`internalFormat`

  Requests the internal storage format of the texture image. The most current version of the SGI implementation of GLU does not check this value for validity before passing it on to the underlying OpenGL implementation. A value that is not accepted by the OpenGL implementation will lead to an OpenGL error. The benefit of not checking this value at the GLU level is that OpenGL extensions can add new internal texture formats without requiring a revision of the GLU implementation. Older implementations of GLU check this value and raise a GLU error if it is not 1, 2, 3, or 4 or one of the following symbolic constants: `GLU_ALPHA`, `GLU_ALPHA4`, `GLU_ALPHA8`, `GLU_ALPHA12`, `GLU_ALPHA16`, `GLU_LUMINANCE`, `GLU_LUMINANCE4`, `GLU_LUMINANCE8`, `GLU_LUMINANCE12`, `GLU_LUMINANCE16`, `GLU_LUMINANCE_ALPHA`, `GLU_LUMINANCE4_ALPHA4`, `GLU_LUMINANCE6_ALPHA2`, `GLU_LUMINANCE8_ALPHA8`, `GLU_LUMINANCE12_ALPHA4`, `GLU_LUMINANCE12_ALPHA12`, `GLU_LUMINANCE16_ALPHA16`, `GLU_INTENSITY`, `GLU_INTENSITY4`, `GLU_INTENSITY8`, `GLU_INTENSITY12`, `GLU_INTENSITY16`, `GLU_RGB`, `GLU_R3_G3_B2`, `GLU_RGB4`, `GLU_RGB5`, `GLU_RGB8`, `GLU_RGB10`, `GLU_RGB12`, `GLU_RGB16`, `GLU_RGBA`, `GLU_RGBA2`, `GLU_RGBA4`, `GLU_RGB5_A1`, `GLU_RGBA8`, `GLU_RGB10_A2`, `GLU_RGBA12`, or `GLU_RGBA16`.

`width`
`height`

  Specifies the width and height, respectively, in pixels of the texture image. These should be a power of 2.

`format`

  Specifies the format of the pixel data. Must be one of `GLU_COLOR_INDEX`, `GLU_DEPTH_COMPONENT`, `GLU_RED`, `GLU_GREEN`, `GLU_BLUE`, `GLU_ALPHA`, `GLU_RGB`, `GLU_RGBA`, `GLU_BGR`, `GLU_BGRA`, `GLU_LUMINANCE`, or `GLU_LUMINANCE_ALPHA`.

`type`

  Specifies the data type for `data`. Must be one of `GLU_UNSIGNED_BYTE`, `GLU_BYTE`, `GLU_BITMAP`, `GLU_UNSIGNED_SHORT`, `GLU_SHORT`, `GLU_UNSIGNED_INT`, `GLU_INT`, `GLU_FLOAT`, `GLU_UNSIGNED_BYTE_3_3_2`, `GLU_UNSIGNED_BYTE_2_3_3_REV`, `GLU_UNSIGNED_SHORT_5_6_5`, `GLU_UNSIGNED_SHORT_5_6_5_REV`, `GLU_UNSIGNED_SHORT_4_4_4_4`, `GLU_UNSIGNED_SHORT_4_4_4_4_REV`, `GLU_UNSIGNED_SHORT_5_5_5_1`, `GLU_UNSIGNED_SHORT_1_5_5_5_REV`, `GLU_UNSIGNED_INT_8_8_8_8`, `GLU_UNSIGNED_INT_8_8_8_8_REV`, `GLU_UNSIGNED_INT_10_10_10_2`, or `GLU_UNSIGNED_INT_2_10_10_10_REV`.

`level`

  Specifies the mipmap level of the image data.

`base`

  Specifies the minimum mipmap level to pass to glTexImage2D.

`max`

  Specifies the maximum mipmap level to pass to glTexImage2D.

`data`

  Specifies a pointer to the image data in memory.

## Description

`gluBuild2DMipmapLevels` builds a subset of prefiltered two-dimensional texture maps of decreasing resolutions called a mipmap. This is used for the antialiasing of texture mapped primitives.

A return value of zero indicates success, otherwise a GLU error code is returned (see gluErrorString).

A series of mipmap levels from `base` to `max` is built by decimating `data` in half along both dimensions until size 1 × 1 is reached. At each level, each texel in the halved mipmap level is an average of the corresponding four texels in the larger mipmap level. (In the case of rectangular images, the decimation will ultimately reach an N × 1 or 1 × N configuration. Here, two texels are averaged instead.) glTexImage2D is called to load these mipmap levels from `base` to `max`. If `max` is larger than the highest mipmap level for the texture of the specified size, then a GLU error code is returned (see gluErrorString) and nothing is loaded.

For example, if `level` is 2 and `width` is 16 and `height` is 8, the following levels are possible: 16 × 8 , 8 × 4 , 4 × 2 , 2 × 1 , 1 × 1 . These correspond to levels 2 through 6 respectively. If `base` is 3 and `max` is 5, then only mipmap levels 8 × 4 , 4 × 2 , and 2 × 1 are loaded. However, if `max` is 7, then an error is returned and nothing is loaded since `max` is larger than the highest mipmap level which is, in this case, 6.

The highest mipmap level can be derived from the formula log 2 &af; max &af; width height × 2 level .

See the glTexImage1D reference page for a description of the acceptable values for `format` parameter. See the glDrawPixels reference page for a description of the acceptable values for `type` parameter.

## Notes

`gluBuild2DMipmapLevels` is only available if the GLU version is 1.3 or greater.

Formats `GLU_BGR`, and `GLU_BGRA`, and types `GLU_UNSIGNED_BYTE_3_3_2`, `GLU_UNSIGNED_BYTE_2_3_3_REV`, `GLU_UNSIGNED_SHORT_5_6_5`, `GLU_UNSIGNED_SHORT_5_6_5_REV`, `GLU_UNSIGNED_SHORT_4_4_4_4`, `GLU_UNSIGNED_SHORT_4_4_4_4_REV`, `GLU_UNSIGNED_SHORT_5_5_5_1`, `GLU_UNSIGNED_SHORT_1_5_5_5_REV`, `GLU_UNSIGNED_INT_8_8_8_8`, `GLU_UNSIGNED_INT_8_8_8_8_REV`, `GLU_UNSIGNED_INT_10_10_10_2`, and `GLU_UNSIGNED_INT_2_10_10_10_REV` are only available if the GL version is 1.2 or greater.

## Errors

`GLU_INVALID_VALUE` is returned if `level` > `base`, `base` < 0, `max` < `base`, or `max` is > the highest mipmap level for `data`.

`GLU_INVALID_VALUE` is returned if `width` or `height` is < 1.

`GLU_INVALID_ENUM` is returned if `internalFormat`, `format`, or `type` is not legal.

`GLU_INVALID_OPERATION` is returned if `type` is `GLU_UNSIGNED_BYTE_3_3_2` or `GLU_UNSIGNED_BYTE_2_3_3_REV` and `format` is not `GLU_RGB`.

`GLU_INVALID_OPERATION` is returned if `type` is `GLU_UNSIGNED_SHORT_5_6_5` or `GLU_UNSIGNED_SHORT_5_6_5_REV` and `format` is not `GLU_RGB`.

`GLU_INVALID_OPERATION` is returned if `type` is `GLU_UNSIGNED_SHORT_4_4_4_4` or `GLU_UNSIGNED_SHORT_4_4_4_4_REV` and `format` is neither `GLU_RGBA` nor `GLU_BGRA`.

`GLU_INVALID_OPERATION` is returned if `type` is `GLU_UNSIGNED_SHORT_5_5_5_1` or `GLU_UNSIGNED_SHORT_1_5_5_5_REV` and `format` is neither `GLU_RGBA` nor `GLU_BGRA`.

`GLU_INVALID_OPERATION` is returned if `type` is `GLU_UNSIGNED_INT_8_8_8_8` or `GLU_UNSIGNED_INT_8_8_8_8_REV` and `format` is neither `GLU_RGBA` nor `GLU_BGRA`.

`GLU_INVALID_OPERATION` is returned if `type` is `GLU_UNSIGNED_INT_10_10_10_2` or `GLU_UNSIGNED_INT_2_10_10_10_REV` and `format` is neither `GLU_RGBA` nor `GLU_BGRA`.

## See Also

gluBuild1DMipmapLevels, gluBuild1DMipmaps, gluBuild2DMipmaps, gluBuild3DMipmapLevels, gluBuild3DMipmaps, gluErrorString, glDrawPixels, glGetTexImage, glGetTexLevelParameter, glTexImage1D, glTexImage2D, glTexImage3D

## 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/.