GLUBUILD2DMIPMAPS(3G)UNIX Programmer's ManuaGLUBUILD2DMIPMAPS(3G)
gluBuild2DMipmaps - builds a two-dimensional mipmap
GLint gluBuild2DMipmaps( GLenum target,
GLint internalFormat,
GLsizei width,
GLsizei height,
GLenum format,
GLenum type,
const void *data )
target Specifies the target texture. Must be
GL_TEXTURE_2D.
internalFormat Requests the internal storage of the tex-
ture 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 implementa-
tion. 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, height Specifies in pixels the width and height,
respectively, of the texture image.
format Specifies the of the pixel data. Must be
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GLUBUILD2DMIPMAPS(3G)UNIX Programmer's ManuaGLUBUILD2DMIPMAPS(3G)
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.
data Specifies a pointer to the image data in
memory.
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 deter-
mine 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 dimen-
sions are clamped to the value returned by glGetIntegerv
with the argument GL_MAX_TEXTURE_SIZE.)
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GLUBUILD2DMIPMAPS(3G)UNIX Programmer's ManuaGLUBUILD2DMIPMAPS(3G)
Next, a series of mipmap levels is built by decimating a
copy of data in half along both dimensions until size 1 x 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 x 1 or 1 x N confi-
guration. 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
log2(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 x 16,
32 x 8, 16 x 4, 8 x 2, 4 x 1, 2 x 1 and 1 x 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.
Note that there is no direct way of querying the maximum
level. This can be derived indirectly via glGetTexLevel-
Parameter. 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 max-
imum level can be derived from the formula
log2(max(width,height)).
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 and if the GLU version is 1.3 or
greater.
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
GL_UNSIGNED_BYTE_3_3_2 or GL_UNSIGNED_BYTE_2_3_3_REV and
format is not GL_RGB.
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GLUBUILD2DMIPMAPS(3G)UNIX Programmer's ManuaGLUBUILD2DMIPMAPS(3G)
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.
glDrawPixels(3G), glTexImage1D(3G), glTexImage2D(3G),
glTexImage3D(3G), gluBuild1DMipmaps(3G),
gluBuild3DMipmaps(3G), gluErrorString(3G),
glGetTexImage(3G), glGetTexLevelParameter(3G),
gluBuild1DMipmapLevels(3G), gluBuild2DMipmapLevels(3G),
gluBuild3DMipmapLevels(3G)
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