GLUBUILD3DMIPMAPS(3G)

💖 GLUBUILD3DMIPMAPS — the 3D mipmap builder 💖

okay bestie, welcome to the GLU manual, section 3G 🎀 this is the page for gluBuild3DMipmaps, and yes it's a whole glow-up for your 3D textures. sit down, hydrate, let's go 🧚

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✨ NAME ✨

gluBuild3DMipmaps — builds a three-dimensional mipmap 🦋

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🌸 C SPECIFICATION 🌸

GLint gluBuild3DMipmaps( GLenum target,
                         GLint internalFormat,
                         GLsizei width,
                         GLsizei height,
                         GLsizei depth,
                         GLenum format,
                         GLenum type,
                         const void *data )

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🎀 PARAMETERS 🎀

• target — specifies the target texture. it must be GL_TEXTURE_3D, no exceptions, no vibes otherwise 💅
• internalFormat — this is the request for how the texture image gets stored internally. now listen, 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. so if the OpenGL implementation doesn't accept it, you get an OpenGL error, periodt 😭 the benefit of not checking at the GLU level is that OpenGL extensions can add brand new internal texture formats without anyone needing to revise the GLU implementation. iconique behavior honestly 👑 older implementations of GLU do check this value, and they raise a GLU error if it isn't 1, 2, 3, or 4, or one of these 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. so many formats bestie, a whole menu 🌈
• width, height, depth — these specify in pixels the width, height and depth respectively, in pixels of the texture image. yes, the manual really says "in pixels" twice. we love redundancy ✨
• 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. pick one, bestie, don't be shy 💜
• 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. that's the whole roster 🔥
• data — specifies a pointer to the image data in memory. hand it over 🫶

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🌈 DESCRIPTION 🌈

gluBuild3DMipmaps builds a series of prefiltered three-dimensional texture maps of decreasing resolutions, and that whole collection is called a mipmap. it's used for the antialiasing of texture-mapped primitives. so like, smoothing out the crunch 💅

a return value of zero means success, otherwise a GLU error code gets returned (see gluErrorString). zero is the good number, remember that ⭐

first things first: the width, height and depth of data are checked to see if they're a power of 2. if they're not, a copy of data (not data itself, bestie, the copy) gets scaled up or down to the nearest power of 2. and here's the lil detail nobody expects: if width, height or depth is exactly between powers of 2, then that copy of data will scale upwards. this copy is what gets used for the 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. math girlies rise 🧚

then, proxy textures (see glTexImage3D) are used to figure out whether the implementation can even fit the requested texture. if it can't, all three dimensions are continually halved until it fits. compromise era 😭

next, a series of mipmap levels gets built by decimating a copy of data in half along all three 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.) averaging is the whole vibe 🎀

glTexImage3D is called to load each of these mipmap levels. Level 0 is a copy of data. the highest level is log2(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: 64×16×32, 32×8×16, 16×4×8, 8×2×4, 4×1×2, 2×1×1 and 1×1×1. these correspond to levels 0 through 6, respectively. look at that glow-down, stunning 🌸

see the glTexImage1D reference page for a description of the acceptable values for the format parameter. see the glDrawPixels reference page for a description of the acceptable values for the type parameter.

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💀 NOTES 💀

heads up: there is no direct way of querying the maximum level. rude, i know 🙈 you can derive it 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. yes. the same words. i'm as shook as you 💀) 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. gatekeeping fr ✋

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. vintage exclusive 💜

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😭 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.
• GLU_INVALID_OPERATION is returned if type is GL_UNSIGNED_INT_10_10_10_2 or GL_UNSIGNED_INT_2_10_10_10_REV and format is neither GL_RGBA nor GL_BGRA.

fr fr, match your type and your format or the GLU will simply not. 💅

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🫶 SEE ALSO 🫶

glDrawPixels(3G), glTexImage1D(3G), glTexImage2D(3G), glTexImage3D(3G), gluBuild1DMipmaps(3G), gluBuild3DMipmaps(3G), gluErrorString(3G), glGetTexImage(3G), glGetTexLevelParameter(3G), gluBuild1DMipmapLevels(3G), gluBuild2DMipmapLevels(3G), gluBuild3DMipmapLevels(3G)

go read the whole friend group, they all ate 🔥

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and that's the page bestie!! this one's from the GLUBUILD3DMIPMAPS(3G) manual, 3G gang forever 💖 mwah, go build some mipmaps, ily, bye 🎀✨🦋