gluBuild2DMipmaps man page on RedHat
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GLUBUILD2DMIPMAPS(3G) OpenGL Manual GLUBUILD2DMIPMAPS(3G)
NAME
gluBuild2DMipmaps - builds a two-dimensional mipmap
C SPECIFICATION
GLint gluBuild2DMipmaps(GLenum target, GLint internalFormat,
GLsizei width, GLsizei height, GLenum format,
GLenum type, 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 in pixels the width and height, respectively, of the
texture image.
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.
data
Specifies a pointer to the image data in memory.
DESCRIPTION
gluBuild2DMipmaps builds a series 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()).
Initially, the width and height of data are checked to see if they are
a power of 2. If not, a copy of data (not data), is scaled up or down
to the nearest power of 2. This copy will be used for subsequent
mipmapping operations described below. (If width or height is exactly
between powers of 2, then the copy of data will scale upwards.) For
example, if width is 57 and height is 23, then a copy of data will
scale up to 64 in width and down to 16 in depth, before mipmapping
takes place.
Then, proxy textures (see glTexImage2D()) are used to determine if the
implementation can fit the requested texture. If not, both dimensions
are continually halved until it fits. (If the OpenGL version is \(<=
1.0, both maximum texture dimensions are clamped to the value returned
by glGetIntegerv() with the argument GLU_MAX_TEXTURE_SIZE.)
Next, a series of mipmap levels is built by decimating a copy of 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 each of these mipmap levels. Level 0
is a copy of data. The highest level is log 2 max width height. For
example, if width is 64 and height is 16 and the implementation can
store a texture of this size, the following mipmap levels are built: 64
× 16, 32 × 8, 16 × 4, 8 × 2, 4 × 1, 2 × 1, and 1 × 1 These correspond
to levels 0 through 6, respectively.
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
Note that there is no direct way of querying the maximum level. This
can be derived indirectly via glGetTexLevelParameter(). First, query
for the width and height actually used at level 0. (The width and
height may not be equal to width and height respectively since proxy
textures might have scaled them to fit the implementation.) Then the
maximum level can be derived from the formula log 2 max width
height.
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 and if the GLU version is 1.3 or greater.
ERRORS
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(),
gluBuild2DMipmapLevels(), 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/.
AUTHORS
opengl.org
opengl.org 03/16/2013 GLUBUILD2DMIPMAPS(3G)
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