Glu.Build1DMipmaps (gb.opengl.glu)

Builds a one-dimensional mipmap.

Parameters

target

Specifies the target texture. Must be Glu.TEXTURE_1D.

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: Glu.ALPHA, Glu.ALPHA4, Glu.ALPHA8, Glu.ALPHA12, Glu.ALPHA16, Glu.LUMINANCE, Glu.LUMINANCE4, Glu.LUMINANCE8, Glu.LUMINANCE12, Glu.LUMINANCE16, Glu.LUMINANCE_ALPHA, Glu.LUMINANCE4_ALPHA4, Glu.LUMINANCE6_ALPHA2, Glu.LUMINANCE8_ALPHA8, Glu.LUMINANCE12_ALPHA4, Glu.LUMINANCE12_ALPHA12, Glu.LUMINANCE16_ALPHA16, Glu.INTENSITY, Glu.INTENSITY4, Glu.INTENSITY8, Glu.INTENSITY12, Glu.INTENSITY16, Glu.RGB, Glu.R3_G3_B2, Glu.RGB4, Glu.RGB5, Glu.RGB8, Glu.RGB10, Glu.RGB12, Glu.RGB16, Glu.RGBA, Glu.RGBA2, Glu.RGBA4, Glu.RGB5_A1, Glu.RGBA8, Glu.RGB10_A2, Glu.RGBA12, or Glu.RGBA16.

width

Specifies the width, in pixels, of the texture image.

format

Specifies the format of the pixel data. Must be one of Glu.COLOR_INDEX, Glu.DEPTH_COMPONENT, Glu.RED, Glu.GREEN, Glu.BLUE, Glu.ALPHA, Glu.RGB, Glu.RGBA, Glu.BGR, Glu.BGRA, Glu.LUMINANCE, or Glu.LUMINANCE_ALPHA.

type

Specifies the data type for data. Must be one of Glu.UNSIGNED_BYTE, Glu.BYTE, Glu.BITMAP, Glu.UNSIGNED_SHORT, Glu.SHORT, Glu.UNSIGNED_INT, Glu.INT, Glu.FLOAT, Glu.UNSIGNED_BYTE_3_3_2, Glu.UNSIGNED_BYTE_2_3_3_REV, Glu.UNSIGNED_SHORT_5_6_5, Glu.UNSIGNED_SHORT_5_6_5_REV, Glu.UNSIGNED_SHORT_4_4_4_4, Glu.UNSIGNED_SHORT_4_4_4_4_REV, Glu.UNSIGNED_SHORT_5_5_5_1, Glu.UNSIGNED_SHORT_1_5_5_5_REV, Glu.UNSIGNED_INT_8_8_8_8, Glu.UNSIGNED_INT_8_8_8_8_REV, Glu.UNSIGNED_INT_10_10_10_2, or Glu.UNSIGNED_INT_2_10_10_10_REV.

data

Specifies a pointer to the image data in memory.

Description

Glu.Build1DMipmaps 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 Glu.ErrorString).

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 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, then a copy of data will scale up to 64 before mipmapping takes place.

Then, proxy textures (see Gl.TexImage1D) 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 $1\times 1$ 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.

Gl.TexImage1D is called to load each of these mipmap levels. Level 0 is a copy of data. The highest level is ${\mathit{log}}_2\left(\mathit{width}\right)$. For example, if width is 64 and the implementation can store a texture of this size, the following mipmap levels are built: $64\times 1$, $32\times 1$, $16\times 1$, $8\times 1$, $4\times 1$, $2\times 1$, and $1\times 1$. These correspond to levels 0 through 6, respectively.

See the Gl.TexImage1D reference page for a description of the acceptable values for the type parameter. See the Gl.DrawPixels 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 Gl.GetTexLevelParameter. 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 ${\mathit{log}}_2\left(\mathit{width}\right)$.

Formats Glu.BGR, and Glu.BGRA, and types Glu.UNSIGNED_BYTE_3_3_2, Glu.UNSIGNED_BYTE_2_3_3_REV, Glu.UNSIGNED_SHORT_5_6_5, Glu.UNSIGNED_SHORT_5_6_5_REV, Glu.UNSIGNED_SHORT_4_4_4_4, Glu.UNSIGNED_SHORT_4_4_4_4_REV, Glu.UNSIGNED_SHORT_5_5_5_1, Glu.UNSIGNED_SHORT_1_5_5_5_REV, Glu.UNSIGNED_INT_8_8_8_8, Glu.UNSIGNED_INT_8_8_8_8_REV, Glu.UNSIGNED_INT_10_10_10_2, and Glu.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.

Errors

Glu.INVALID_VALUE is returned if width is < 1.

Glu.INVALID_ENUM is returned if format or type are not legal.

Glu.INVALID_OPERATION is returned if type is Glu.UNSIGNED_BYTE_3_3_2 or Glu.UNSIGNED_BYTE_2_3_3_REV and format is not Glu.RGB.

Glu.INVALID_OPERATION is returned if type is Glu.UNSIGNED_SHORT_5_6_5 or Glu.UNSIGNED_SHORT_5_6_5_REV and format is not Glu.RGB.

Glu.INVALID_OPERATION is returned if type is Glu.UNSIGNED_SHORT_4_4_4_4 or Glu.UNSIGNED_SHORT_4_4_4_4_REV and format is neither Glu.RGBA nor Glu.BGRA.

Glu.INVALID_OPERATION is returned if type is Glu.UNSIGNED_SHORT_5_5_5_1 or Glu.UNSIGNED_SHORT_1_5_5_5_REV and format is neither Glu.RGBA nor Glu.BGRA.

Glu.INVALID_OPERATION is returned if type is Glu.UNSIGNED_INT_8_8_8_8 or Glu.UNSIGNED_INT_8_8_8_8_REV and format is neither Glu.RGBA nor Glu.BGRA.

Glu.INVALID_OPERATION is returned if type is Glu.UNSIGNED_INT_10_10_10_2 or Glu.UNSIGNED_INT_2_10_10_10_REV and format is neither Glu.RGBA nor Glu.BGRA.

See also

See original documentation on OpenGL website