# gluBuild1DMipmapLevels.3G - Man Page

builds a subset of one-dimensional mipmap levels

## C Specification

GLint gluBuild1DMipmapLevels( GLenum target,

```	GLint internalFormat,
GLsizei width,
GLenum format,
GLenum type,
GLint level,
GLint base,
GLint max,
const void *data )```

## Parameters

target

Specifies the target texture.  Must be GL_TEXTURE_1D.

internalFormat

Requests the internal storage  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: GL_ALPHA, GL_ALPHA4, GL_ALPHA8, GL_ALPHA12, GL_ALPHA16, GL_LUMINANCE, GL_LUMINANCE4, GL_LUMINANCE8, GL_LUMINANCE12, GL_LUMINANCE16, GL_LUMINANCE_ALPHA, GL_LUMINANCE4_ALPHA4, GL_LUMINANCE6_ALPHA2, GL_LUMINANCE8_ALPHA8, GL_LUMINANCE12_ALPHA4, GL_LUMINANCE12_ALPHA12, GL_LUMINANCE16_ALPHA16, GL_INTENSITY, GL_INTENSITY4, GL_INTENSITY8, GL_INTENSITY12, GL_INTENSITY16, GL_RGB, GL_R3_G3_B2, GL_RGB4, GL_RGB5, GL_RGB8, GL_RGB10, GL_RGB12, GL_RGB16, GL_RGBA, GL_RGBA2, GL_RGBA4, GL_RGB5_A1, GL_RGBA8, GL_RGB10_A2, GL_RGBA12 or GL_RGBA16.

width

Specifies the width in pixels of the texture image.  This should be a power of 2.

format

Specifies the  of the pixel data. Must be one of: GL_COLOR_INDEX, GL_DEPTH_COMPONENT, GL_RED, GL_GREEN, GL_BLUE, GL_ALPHA, GL_RGB, GL_RGBA, GL_BGR, GL_BGRA, GL_LUMINANCE, or GL_LUMINANCE_ALPHA.

type

Specifies the data type for data. Must be one of: GL_UNSIGNED_BYTE, GL_BYTE, GL_BITMAP, GL_UNSIGNED_SHORT, GL_SHORT, GL_UNSIGNED_INT, GL_INT,  GL_FLOAT,  GL_UNSIGNED_BYTE_3_3_2, GL_UNSIGNED_BYTE_2_3_3_REV, GL_UNSIGNED_SHORT_5_6_5, GL_UNSIGNED_SHORT_5_6_5_REV, GL_UNSIGNED_SHORT_4_4_4_4, GL_UNSIGNED_SHORT_4_4_4_4_REV, GL_UNSIGNED_SHORT_5_5_5_1, GL_UNSIGNED_SHORT_1_5_5_5_REV, GL_UNSIGNED_INT_8_8_8_8, GL_UNSIGNED_INT_8_8_8_8_REV, GL_UNSIGNED_INT_10_10_10_2, or GL_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 glTexImage1D.

max

Specifies the maximum mipmap level to pass to glTexImage1D.

data

Specifies a pointer to the image data in memory.

## Description

gluBuild1DMipmapLevels builds a subset of prefiltered one-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  until size $1\text{ }×\text{ }1$ is reached. At each level, each texel in the halved mipmap level is an average of the corresponding two texels in the larger mipmap level.  glTexImage1D 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, the following levels are possible: $16\text{ }×\text{ }1$, $8\text{ }×\text{ }1$, $4\text{ }×\text{ }1$, $2\text{ }×\text{ }1$, $1\text{ }×\text{ }1$. These correspond to levels 2 through 6 respectively. If base is 3 and max is 5, then only mipmap levels $8\text{ }×\text{ }1$, $4\text{ }×\text{ }1$ and $2\text{ }×\text{ }1$ 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 ${\text{log}}_{2}\left(\text{\f2}width\text{}{2}^{\text{\f2}level}\right)$.

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

## Notes

gluBuild1DMipmapLevels is only available if the GLU version is 1.3 or greater.

Formats GL_BGR, and GL_BGRA, and types  GL_UNSIGNED_BYTE_3_3_2, GL_UNSIGNED_BYTE_2_3_3_REV, GL_UNSIGNED_SHORT_5_6_5, GL_UNSIGNED_SHORT_5_6_5_REV, GL_UNSIGNED_SHORT_4_4_4_4, GL_UNSIGNED_SHORT_4_4_4_4_REV, GL_UNSIGNED_SHORT_5_5_5_1, GL_UNSIGNED_SHORT_1_5_5_5_REV, GL_UNSIGNED_INT_8_8_8_8, GL_UNSIGNED_INT_8_8_8_8_REV, GL_UNSIGNED_INT_10_10_10_2, and GL_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 is < 1.

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

GLU_INVALID_OPERATION is returned if type is GL_UNSIGNED_BYTE_3_3_2 or GL_UNSIGNED_BYTE_2_3_3_REV and format is not GL_RGB.

GLU_INVALID_OPERATION is returned if type is GL_UNSIGNED_SHORT_5_6_5 or GL_UNSIGNED_SHORT_5_6_5_REV and format is not GL_RGB.

GLU_INVALID_OPERATION is returned if type is GL_UNSIGNED_SHORT_4_4_4_4 or GL_UNSIGNED_SHORT_4_4_4_4_REV and format is neither GL_RGBA nor GL_BGRA.

GLU_INVALID_OPERATION is returned if type is GL_UNSIGNED_SHORT_5_5_5_1 or GL_UNSIGNED_SHORT_1_5_5_5_REV and format is neither GL_RGBA nor GL_BGRA.

GLU_INVALID_OPERATION is returned if type is GL_UNSIGNED_INT_8_8_8_8 or GL_UNSIGNED_INT_8_8_8_8_REV and format is neither GL_RGBA nor GL_BGRA.

GLU_INVALID_OPERATION is returned if type is GL_UNSIGNED_INT_10_10_10_2 or GL_UNSIGNED_INT_2_10_10_10_REV and format is neither GL_RGBA nor GL_BGRA.