gluBuild1DMipmapLevels Subroutine

Purpose

Builds a subset of 1D mipmap levels.

Library

OpenGL C bindings library: libGL.a

C Syntax

GLint gluBuild1DMipmapLevels( GLenum target,
   GLint internalFormat,
   GLsizei width,
   GLenum format,
   GLenum type,
   GLint level,
   GLint base,
   GLint max,
   const void *data )

Description

gluBuild1DMipmapLevels builds a subset of prefiltered 1D texture maps of decreasing resolutions called a mipmap. This is used for the antialiasing of texture mapped primitives.

A return value of 0 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 1x1 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: 16x1, 8x1, 4x1, 2x1, 1x1. These correspond to levels 2 through 6 respectively. If base is 3 and max is 5, then only mipmap levels 8x1, 4x1 and 2x1 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 log2(width)*(2^level)). 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.

Parameters

Error Codes

• 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 level is GL_UNSIGNED_BYTE_3_3_2 or GL_UNSIGNED_BYTE_2_3_3_REV and type is not GL_RGB.
• GLU_INVALID_OPERATION is returned if level is GL_UNSIGNED_SHORT_5_6_5 or GL_UNSIGNED_SHORT_5_6_5_REV and type is not GL_RGB.
• GLU_INVALID_OPERATION is returned if level is GL_UNSIGNED_SHORT_4_4_4_4 or GL_UNSIGNED_SHORT_4_4_4_4_REV and type is neither GL_RGBA nor GL_BGRA.
• GLU_INVALID_OPERATION is returned if level is GL_UNSIGNED_SHORT_5_5_5_1 or GL_UNSIGNED_SHORT_1_5_5_5_REV and type is neither GL_RGBA nor GL_BGRA.
• GLU_INVALID_OPERATION is returned if level is GL_UNSIGNED_INT_8_8_8_8 or GL_UNSIGNED_INT_8_8_8_8_REV and type is neither GL_RGBA nor GL_BGRA.
• GLU_INVALID_OPERATION is returned if level is GL_UNSIGNED_INT_10_10_10_2 or GL_UNSIGNED_INT_2_10_10_10_REV and type is neither GL_RGBA nor GL_BGRA.

Files

Related Information

The glDrawPixels subroutine, glTexImage1D subroutine, glTexImage2D subroutine, glTexImage3D subroutine, gluBuild1DMipmaps subroutine, gluBuild2DMipmaps subroutine, gluBuild3DMipmaps subroutine, gluErrorString subroutine, glGetTexImage subroutine, glGetTexLevelParameter subroutine, gluBuild2DMipmapLevels subroutine and gluBuild3DMipmapLevels subroutine.