fgluBuild2DMipmaps(3G) OpenGL Reference fgluBuild2DMipmaps(3G)NAME
fgluBuild2DMipmaps - builds a two-dimensional mipmap
FORTRAN SPECIFICATION
INTEGER*4 fgluBuild2DMipmaps( INTEGER*4 target,
INTEGER*4 internalFormat,
INTEGER*4 width,
INTEGER*4 height,
INTEGER*4 format,
INTEGER*4 type,
void data )
PARAMETERS
target Specifies the target texture. Must be GL_TEXTURE_2D.
internalFormat Requests the internal storage format of the texture
image. Must be 1, 2, 3, 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 format 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.
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fgluBuild2DMipmaps(3G) OpenGL Reference fgluBuild2DMipmaps(3G)
data Specifies a pointer to the image data in memory.
DESCRIPTION
fgluBuild2DMipmaps 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 fgluErrorString).
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 GL_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 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
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 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.
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 log2(max(width,height)).
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fgluBuild2DMipmaps(3G) OpenGL Reference fgluBuild2DMipmaps(3G)NOTES
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.
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 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.
SEE ALSO
glDrawPixels, glTexImage1D, glTexImage2D, glTexImage3D,
fgluBuild1DMipmaps, fgluBuild3DMipmaps, fgluErrorString, glGetTexImage,
glGetTexLevelParameter, fgluBuild1DMipmapLevels, fgluBuild2DMipmapLevels,
fgluBuild3DMipmapLevels
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