gluBuild3DMipmapLevels

gluBuild3DMipmapLevels: man2/gluBuild3DMipmapLevels.xml

gluBuild3DMipmapLevels builds a subset 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 ). A series of mipmap levels from base to max is built by decimating data in half along both dimensions until size 1 × 1 × 1 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 these mipmap levels from base to max. If max is larger than the highest mipmap level for the texture of the specified size, then a GLU error code is returned (see gluErrorString ) and nothing is loaded. For example, if level is 2 and width is 16, height is 8 and depth is 4, the following levels are possible: 16 × 8 × 4, 8 × 4 × 2, 4 × 2 × 1, 2 × 1 × 1, 1 × 1 × 1. These correspond to levels 2 through 6 respectively. If base is 3 and max is 5, then only mipmap levels 8 × 4 × 2, 4 × 2 × 1, and 2 × 1 × 1 are loaded. However, if max is 7, then an error is returned and nothing is loaded, since max is larger than the highest mipmap level which is, in this case, 6. The highest mipmap level can be derived from the formula log 2 ⁡ max ⁡ width height depth × 2 level. 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.

gluBuild3DMipmapLevels is only available if the GLU version is 1.3 or greater. 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.