GLUBUILD1DMIPMAPS(3G)GLUBUILD1DMIPMAPS(3G)NAMEgluBuild1DMipmaps - builds a one-dimensional mipmap
C SPECIFICATION
GLint gluBuild1DMipmaps( GLenum target,
GLint internalFormat,
GLsizei width,
GLenum format,
GLenum type,
const void *data )
delim $$
PARAMETERS
target Specifies the target texture. Must be GL_TEXTURE_1D.
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 Specifies the width, in pixels, of the texture image.
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,
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.
DESCRIPTIONgluBuild1DMipmaps builds a series of prefiltered one-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 of data is checked to see if it is a power of 2.
If not, a copy of data is scaled up or down to the nearest power of 2.
(If width is exactly between powers of 2, then the copy of data will
scale upwards.) This copy will be used for subsequent mipmapping
operations described below. For example, if width is 57 then a copy of
data will scale up to 64 before mipmapping takes place.
Then, proxy textures (see glTexImage1D) are used to determine if the
implementation can fit the requested texture. If not, width is
continually halved until it fits.
Next, a series of mipmap levels is built by decimating a copy of data
in half until size $1 ~times~ 1$ 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 each of these mipmap levels. Level 0 is
a copy of data. The highest level is ${log sub 2}(width)$. For
example, if width is 64 and the implementation can store a texture of
this size, the following mipmap levels are built: $64 ~times~ 1$, $32
~times~ 1$, $16 ~times~ 1$, $8 ~times~ 1$, $4 ~times~ 1$, $2 ~times~ 1$
and $1 ~times~ 1$. These correspond to levels 0 through 6,
respectively.
See the glTexImage1D reference page for a description of the acceptable
values for the type parameter. See the glDrawPixels reference page for
a description of the acceptable values for the data 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 actually used at level 0. (The width may not be equal to
width since proxy textures might have scaled it to fit the
implementation.) Then the maximum level can be derived from the
formula ${log sub 2}(width)$.
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 is < 1.
GLU_INVALID_ENUM is returned if format or type are 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 ALSOglDrawPixels(3G), glTexImage1D(3G), glTexImage2D(3G), glTexImage3D(3G),
gluBuild2DMipmaps(3G), gluBuild3DMipmaps(3G), gluErrorString(3G),
glGetTexImage(3G), glGetTexLevelParameter(3G),
gluBuild1DMipmapLevels(3G), gluBuild2DMipmapLevels(3G),
gluBuild3DMipmapLevels(3G)
March 1, 2011
