gluBuild1DMipmaps() gluBuild1DMipmaps()
gluBuild1DMipmaps - builds a 1-D mipmap
GLint gluBuild1DMipmaps(
GLenum target,
GLint internalFormat,
GLsizei width,
GLenum format,
GLenum type,
const void *data );
Specifies the target texture. Must be GL_TEXTURE_1D.
Requests the internal storage format of the texture image.
Must be 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.
Specifies the width, in pixels, of the texture image.
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, and GL_LUMINANCE_ALPHA.
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, or GL_FLOAT. Specifies
a pointer to the image data in memory.
gluBuild1DMipmaps() builds a series of prefiltered 1-D
texture maps of decreasing resolutions called a mipmap.
This is 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 (not 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.
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 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[2](width). For example, if width is 64 and the implementation
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, respectively.
See the glTexImage1D() reference page for a description of
the acceptable values for type. See the glDrawPixels()
reference page for a description of the acceptable values
for data.
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
log2(width).
GLU_INVALID_VALUE is returned if width is < 1.
GLU_INVALID_ENUM is returned if internalFormat, format or
type are not legal.
glDrawPixels(3), glTexImage1D(3), , glTexImage2D(3),
gluBuild2DMipmaps(3), gluErrorString(3), gluScaleImage(3),
gluBuild1DMipmaps()
[ Back ] |
