glubuild1dmipmaps
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gluBuild1DMipmaps(3G) OpenGL Reference gluBuild1DMipmaps(3G)
NAME
gluBuild1DMipmaps - builds 1-D mipmaps
C SPECIFICATION
GLint gluBuild1DMipmaps( GLenum target,
GLint component,
GLsizei width,
GLenum format,
GLenum type,
const void *data )
PARAMETERS
target Specifies the target texture. Must be GL_TEXTURE_1D.
component Specifies the number of color components in the texture. Must
be 1, 2, 3, or 4 or one of the following symbolic constants:
GL_ALPHA, GL_INTENSITY_EXT, GL_LUMINANCE, GL_LUMINANCE_ALPHA,
GL_RGB, GL_RGBA.
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_RED, GL_GREEN, GL_BLUE, GL_ALPHA, GL_RGB,
GL_RGBA, GL_LUMINANCE, GL_LUMINANCE_ALPHA and GL_ABGR_EXT.
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_EXT, GL_UNSIGNED_SHORT_4_4_4_4_EXT,
GL_UNSIGNED_SHORT_5_5_5_1_EXT, GL_UNSIGNED_INT_8_8_8_8_EXT,
and GL_UNSIGNED_INT_10_10_10_2_EXT.
data Specifies a pointer to the image data in memory.
DESCRIPTION
gluBuild1DMipmaps builds a series of prefiltered 1-D texture maps of
decreasing resolutions called mipmaps. These are used for the
antialiasing of texture mapped primitives.
A return value of 0 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 two.
If not, a copy of data is scaled up or down to the nearest power of two.
This copy will be used for subsequent mipmapping operations described
below. (If width is exactly between powers of 2, then the copy of data
will scale upwards.) For example, if width is 57 then a copy of data
will scale up to 64 before mipmapping takes place.
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gluBuild1DMipmaps(3G) OpenGL Reference gluBuild1DMipmaps(3G)
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 mipmaps is built by decimating a copy of data in half
until size 1 is reached. At each level, each texel in the halved mipmap
is an average of the corresponding two texels in the larger mipmap.
glTexImage1D is called to load each of these mipmaps by level. Level 0
is a copy of data. The highest level is log2(width). For example, if
width is 64 and the implementation can store a texture of this size, the
following mipmaps are built: 64x1, 32x1, 16x1, 8x1, 4x1, 2x1 and 1x1.
These correspond to levels 0 through 6, respectively.
Please refer to 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 queried indirectly via glGetTexLevelParameter. First, query for the
width actually used at level 0. (The width may be <= width since proxy
textures might have strunk it to fit the implementation.) Then the
maximum level can be derived from the formula log2(width).
ERRORS
GLU_INVALID_VALUE is returned if width is < 1.
GLU_INVALID_ENUM is returned if format or type are not legal.
GLU_INVALID_ENUM is returned if type is GL_UNSIGNED_BYTE_3_3_2_EXT and
format is not GL_RGB.
GLU_INVALID_ENUM is returned if type is GL_UNSIGNED_SHORT_4_4_4_4_EXT and
format is neither GL_RGBA nor GL_ABGR_EXT.
GLU_INVALID_ENUM is returned if type is GL_UNSIGNED_SHORT_5_5_5_1_EXT and
format is neither GL_RGBA nor GL_ABGR_EXT.
GLU_INVALID_ENUM is returned if type is GL_UNSIGNED_INT_8_8_8_8_EXT and
format is neither GL_RGBA nor GL_ABGR_EXT.
GLU_INVALID_ENUM is returned if type is GL_UNSIGNED_INT_10_10_10_2_EXT
and format is neither GL_RGBA nor GL_ABGR_EXT.
BUGS
Passing GL_STENCIL_INDEX or GL_DEPTH_COMPONENT as format will incorrectly
return 0 and set the error code to GL_INVALID_ENUM. It should return
GLU_INVALID_ENUM and not set an error code.
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gluBuild1DMipmaps(3G) OpenGL Reference gluBuild1DMipmaps(3G)
SEE ALSO
glDrawPixels, glTexImage1D, glTexImage2D, gluBuild2DMipmaps,
gluErrorString, glGetTexImage, glGetTexLevelParameter.
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