|
Table of Contents
gluBuild2DMipmaps - builds a two-dimensional mipmap
GLint
gluBuild2DMipmaps( GLenum target,
GLint internalFormat,
GLsizei width,
GLsizei height,
GLenum format,
GLenum type,
const void *data )
eqn not supported
- 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 in pixels the width and height, respectively,
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, 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.
- data
- Specifies a pointer to the image data in memory.
gluBuild2DMipmaps
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 gluErrorString).
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 $1 ~times~ 1$ 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 each of these mipmap
levels. Level 0 is a copy of data. The highest level is ${log sub 2} ( max
("width","height"))$. 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: $64 ~times~ 16$, $32 ~times~ 8$, $16 ~times~ 4$, $8 ~times~
2$, $4 ~times~ 1$, $2 ~times~ 1$ 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 format parameter. See the glDrawPixels
reference page for a description of the acceptable values for type parameter.
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 ${log sub 2}( max (width,height))$.
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.
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.
glDrawPixels(3G)
, glTexImage1D(3G)
,
glTexImage2D(3G)
, glTexImage3D(3G)
, gluBuild1DMipmaps(3G)
, gluBuild3DMipmaps(3G)
,
gluErrorString(3G)
, glGetTexImage(3G)
, glGetTexLevelParameter(3G)
, gluBuild1DMipmapLevels(3G)
,
gluBuild2DMipmapLevels(3G)
, gluBuild3DMipmapLevels(3G)
Table of Contents
|
