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GLUBUILD2DMIPMAPSIndexNAMEgluBuild2DMipmaps - builds a two-dimensional mipmapC SPECIFICATIONGLint f3gluBuild2DMipmapsfP( GLenum fItargetfP,f2targetfP Specifies the target texture. Must be %f3GL_TEXTURE_2DfP.
DESCRIPTION%f3gluBuild2DMipmapsfP 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 %f3gluErrorStringfP). Initially, the f2widthfP and f2heightfP of f2datafP are checked to see if they are a power of 2. If not, a copy of f2datafP (not f2datafP), is scaled up or down to the nearest power of 2. This copy will be used for subsequent mipmapping operations described below. (If f2widthfP or f2heightfP is exactly between powers of 2, then the copy of f2datafP will scale upwards.) For example, if f2widthfP is 57 and f2heightfP is 23 then a copy of f2datafP will scale up to 64 in f2widthfP and down to 16 in depth, before mipmapping takes place. Then, proxy textures (see f3glTexImage2DfP) 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 f3glGetIntegervfP with the argument %f3GL_MAX_TEXTURE_SIZEfP.) Next, a series of mipmap levels is built by decimating a copy of f2datafP 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.) f3glTexImage2DfP is called to load each of these mipmap levels. Level 0 is a copy of f2datafP. The highest level is ${log sub 2} ( max ("width","height"))$. For example, if f2widthfP is 64 and f2heightfP 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 f3glTexImage1DfP reference page for a description of the acceptable values for f2formatfP parameter. See the f3glDrawPixelsfP reference page for a description of the acceptable values for f2typefP parameter.NOTESNote that there is no direct way of querying the maximum level. This can be derived indirectly via f3glGetTexLevelParameterfP. First, query for the width and height actually used at level 0. (The width and height may not be equal to f2widthfP and f2heightfP respectively since proxy textures might have scaled them to fit the implementation.) Then the maximum level can be derived from the formula ${log sub 2}( max (f2widthfP,f2heightfP))$. NOTESFormats %f3GL_BGRfP, and %f3GL_BGRAfP, and types %f3GL_UNSIGNED_BYTE_3_3_2fP, %f3GL_UNSIGNED_BYTE_2_3_3_REVfP, %f3GL_UNSIGNED_SHORT_5_6_5fP, %f3GL_UNSIGNED_SHORT_5_6_5_REVfP, %f3GL_UNSIGNED_SHORT_4_4_4_4fP, %f3GL_UNSIGNED_SHORT_4_4_4_4_REVfP, %f3GL_UNSIGNED_SHORT_5_5_5_1fP, %f3GL_UNSIGNED_SHORT_1_5_5_5_REVfP, %f3GL_UNSIGNED_INT_8_8_8_8fP, %f3GL_UNSIGNED_INT_8_8_8_8_REVfP, %f3GL_UNSIGNED_INT_10_10_10_2fP, and %f3GL_UNSIGNED_INT_2_10_10_10_REVfP are only available if the GL version is 1.2 or greater and if the GLU version is 1.3 or greater.ERRORS%f3GLU_INVALID_VALUEfP is returned if f2widthfP, or f2heightfP is < 1. %f3GLU_INVALID_ENUMfP is returned if f2internalFormatfP, f2formatfP, or f2typefP is not legal. %f3GLU_INVALID_OPERATIONfP is returned if f2typefP is %f3GL_UNSIGNED_BYTE_3_3_2fP or %f3GL_UNSIGNED_BYTE_2_3_3_REVfP and f2formatfP is not %f3GL_RGBfP. %f3GLU_INVALID_OPERATIONfP is returned if f2typefP is %f3GL_UNSIGNED_SHORT_5_6_5fP or %f3GL_UNSIGNED_SHORT_5_6_5_REVfP and f2formatfP is not %f3GL_RGBfP. %f3GLU_INVALID_OPERATIONfP is returned if f2typefP is %f3GL_UNSIGNED_SHORT_4_4_4_4fP or %f3GL_UNSIGNED_SHORT_4_4_4_4_REVfP and f2formatfP is neither %f3GL_RGBAfP nor %f3GL_BGRAfP. %f3GLU_INVALID_OPERATIONfP is returned if f2typefP is %f3GL_UNSIGNED_SHORT_5_5_5_1fP or %f3GL_UNSIGNED_SHORT_1_5_5_5_REVfP and f2formatfP is neither %f3GL_RGBAfP nor %f3GL_BGRAfP. %f3GLU_INVALID_OPERATIONfP is returned if f2typefP is %f3GL_UNSIGNED_INT_8_8_8_8fP or %f3GL_UNSIGNED_INT_8_8_8_8_REVfP and f2formatfP is neither %f3GL_RGBAfP nor %f3GL_BGRAfP. %f3GLU_INVALID_OPERATIONfP is returned if f2typefP is %f3GL_UNSIGNED_INT_10_10_10_2fP or %f3GL_UNSIGNED_INT_2_10_10_10_REVfP and f2formatfP is neither %f3GL_RGBAfP nor %f3GL_BGRAfP.SEE ALSOf3glDrawPixels(3G)fP, f3glTexImage1D(3G)fP, f3glTexImage2D(3G)fP, f3glTexImage3D(3G)fP, %f3gluBuild1DMipmaps(3G)fP, %f3gluBuild3DMipmaps(3G)fP, %f3gluErrorString(3G)fP, f3glGetTexImage(3G)fP, f3glGetTexLevelParameter(3G)fP, %f3gluBuild1DMipmapLevels(3G)fP, %f3gluBuild2DMipmapLevels(3G)fP, %f3gluBuild3DMipmapLevels(3G)fP
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