NAME

gluBuild3DMipmaps - builds a three-dimensional mipmap

C SPECIFICATION

GLint gluBuild3DMipmaps( GLenum target,

	GLint internalFormat,
	GLsizei width,
	GLsizei height,
	GLsizei depth,
	GLenum format,
	GLenum type,
	const void *data )

PARAMETERS

target: Specifies the target texture. Must be GL_TEXTURE_3D.
internalFormat: Requests the internal storage format 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, depth: Specifies in pixels the width, height and depth respectively, 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, 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.

DESCRIPTION

gluBuild3DMipmaps builds a series of prefiltered three-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, height and depth 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. (If width, height or depth 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, height is 23 and depth is 24 then a copy of data will scale up to 64 in width, down to 16 in height and up to 32 in depth, before mipmapping takes place.

Then, proxy textures (see glTexImage3D) are used to determine if the implementation can fit the requested texture. If not, all three dimensions are continually halved until it fits.

Next, a series of mipmap levels is built by decimating a copy of data in half along all three dimensions until size 1x1x1 is reached. At each level, each texel in the halved mipmap level is an average of the corresponding eight texels in the larger mipmap level. (If exactly one of the dimensions is 1, four texels are averaged. If exactly two of the dimensions are 1, two texels are averaged.)

glTexImage3D 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","depth")). For example, if width is 64, height is 16 and depth is 32, and the implementation can store a texture of this size, the following mipmap levels are built: 64x16x32, 32x8x16, 16x4x8, 8x2x4, 4x1x2, 2x1x1 and 1x1x1. 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.

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, height and depth actually used at level 0. (The width, height and depth may not be equal to width, height and depth respectively since proxy textures might have scaled them to fit the implementation.) Then the maximum level can be derived from the formula log2 ( max (width,height,depth)).

gluBuild3DMipmaps is only available if the GLU version is 1.3 or greater.

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.

ERRORS

GLU_INVALID_VALUE is returned if width, height, or depth 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.