gluBuild1DMipmaps - builds a one-dimensional mipmap
C SPECIFICATION
GLint gluBuild1DMipmaps( GLenum target,
GLint internalFormat,
GLsizei width,
GLenum format,
GLenum type,
const void *data )
PARAMETERS
target Specifies the target texture. Must be
GL_TEXTURE_1D.
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 Specifies the width, in pixels, 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,
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,
DESCRIPTION
gluBuild1DMipmaps 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 pow-
ers 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 deter-
mine 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 1x1 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 lev-
els. Level 0 is a copy of data. The highest level is
log2(width). For example, if width is 64 and the imple-
mentation can store a texture of this size, the following
mipmap levels are built: 64x1, 32x1, 16x1, 8x1, 4x1, 2x1
and 1x1. These correspond to levels 0 through 6, respec-
tively.
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 glGetTexLevelPa-
rameter. First, query for the width actually used at level
0. (The width may not be equal to width since proxy tex-
tures might have scaled it to fit the implementation.)
Then the maximum level can be derived from the formula
log2(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,
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,
gluBuild2DMipmaps, gluBuild3DMipmaps, gluErrorString,
glGetTexImage, glGetTexLevelParameter,
gluBuild1DMipmapLevels, gluBuild2DMipmapLevels,
gluBuild3DMipmapLevels
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