GLUBUILD2DMIPMAPLEVELS
Section: Misc. Reference Manual Pages (3G)
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NAME
gluBuild2DMipmapLevels
- builds a subset of two-dimensional mipmap levels
C SPECIFICATION
GLint
gluBuild2DMipmapLevels(
GLenum
target,
GLint internalFormat,
GLsizei width,
GLsizei height,
GLenum format,
GLenum type,
GLint level,
GLint base,
GLint max,
const void *data )
delim $$
PARAMETERS
- target
-
Specifies the target texture. Must be GL_TEXTURE_2D.
- 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, height
-
Specifies the width and height, respectively, in pixels of the texture image.
These 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 glTexImage2D.
- max
-
Specifies the maximum mipmap level to pass to glTexImage2D.
- data
-
Specifies a pointer to the image data in memory.
DESCRIPTION
gluBuild2DMipmapLevels builds a subset 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).
A series of mipmap levels from base to max is built by decimating
data in half along
both dimensions until size $1 ~times~ 1$ 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 $N ~times~ 1$ or $1 ~times~ N$ configuration. Here, two texels are
averaged instead.)
glTexImage2D 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 and height is 8, the
following levels are possible: $16 ~times~ 8$, $8 ~times~ 4$, $4 ~times~ 2$,
$2 ~times~ 1$, $1 ~times~ 1$. These correspond to levels 2 through 6
respectively. If base is 3 and max is 5, then only mipmap levels
$8 ~times~ 4$, $4 ~times~ 2$ and $2 ~times~ 1$ 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
log2(max(width,height)*(2^level)).
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
gluBuild2DMipmapLevels 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 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(3G),
glTexImage1D(3G),
glTexImage2D(3G),
glTexImage3D(3G),
gluBuild1DMipmaps(3G),
gluBuild2DMipmaps(3G),
gluBuild3DMipmaps(3G),
gluErrorString(3G),
glGetTexImage(3G),
glGetTexLevelParameter(3G),
gluBuild1DMipmapLevels(3G),
gluBuild3DMipmapLevels(3G)