GLUBUILD3DMIPMAPLEVELS(3G)

📦 version 1.1, in centos-stream 9, fedora 43, fedora 44

👑 GLUBUILD3DMIPMAPLEVELS 💅

okay so bestie, welcome to the 3G manual page for gluBuild3DMipmapLevels — yes, the whole squad is here, it's giving mipmap subset builder energy and honestly? obsessed.

This is the page that builds a subset of three-dimensional mipmap levels. Periodt.

✨ C SPECIFICATION ✨

GLint gluBuild3DMipmapLevels( GLenum target,
                              GLint internalFormat,
                              GLsizei width,
                              GLsizei height,
                              GLsizei depth,
                              GLenum format,
                              GLenum type,
                              GLint level,
                              GLint base,
                              GLint max,
                              const void *data )

look at that parameter list. eleven args. she ate and left no crumbs 💅

🎀 PARAMETERS 🎀

  • target — specifies the target texture. it must be GL_TEXTURE_3D. no other option, no negotiating, that's the vibe check 🦋
  • internalFormat — requests the internal storage of the texture image. here's the tea though: 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 you hand it a value that isn't accepted by the OpenGL implementation, that's gonna lead to an OpenGL error — not our problem, bestie 😭. the whole benefit of not checking this at the GLU level is that OpenGL extensions can add brand new internal texture formats without requiring a revision of the GLU implementation. iconic foresight honestly. ✨
older implementations of GLU do check this value, and they raise a GLU error if it's not 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. that's the whole list, no skipping 🫶
  • width, height, depth — specifies, in pixels, the width, height and depth respectively of the texture image. these should be a power of 2. lowkey important, don't fight it 💜
  • format — specifies the of the pixel data (the original page fr left a word out right there, we keep it moving 💀). 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. that's a lot of types and yes you have to pick one 🧚
  • level — specifies the mipmap level of the image data.
  • base — specifies the minimum mipmap level to pass to glTexImage3D.
  • max — specifies the maximum mipmap level to pass to glTexImage3D.
  • data — specifies a pointer to the image data in memory. 🍓

🌈 DESCRIPTION 🌈

okay so gluBuild3DMipmapLevels builds a subset of prefiltered three-dimensional texture maps of decreasing resolutions called a mipmap. this is what gets used for the antialiasing of texture mapped primitives. main character behavior ✨

A return value of zero indicates success — otherwise a GLU error code is returned (see gluErrorString). zero = slay, anything else = we're in our flop era 😭

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. and here's the warning bestie, listen up:

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. nothing. zero. nada. 💀

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. see how that works? chef's kiss 🎀

The highest mipmap level can be derived from the formula

log2(max(width,height,depth)2level)

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. iykyk 📚

💜 NOTES 💜

  • gluBuild3DMipmapLevels is only available if the GLU version is 1.3 or greater. no old-school GLU for you, sorry not sorry 🙈
  • 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 🔥

this is the section where we find out if you did it right. deep breaths bestie, here's every single way this can go wrong:

  • GLU_INVALID_VALUE is returned if level > base, base < 0, max < base or max is > the highest mipmap level for data.
  • 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.

🦋 SEE ALSO 🦋

the whole friend group, go say hi:

  • glDrawPixels(3G)
  • glTexImage1D(3G)
  • glTexImage2D(3G)
  • glTexImage3D(3G)
  • gluBuild1DMipmaps(3G)
  • gluBuild2DMipmaps(3G)
  • gluBuild3DMipmaps(3G)
  • gluErrorString(3G)
  • glGetTexImage(3G)
  • glGetTexLevelParameter(3G)
  • gluBuild1DMipmapLevels(3G)
  • gluBuild2DMipmapLevels(3G)

and that's the page bestie!! 🫶 this whole thing lives under the name GLUBUILD3DMIPMAPLEVELS(3G) and the footer just says the same thing back to you — GLUBUILD3DMIPMAPLEVELS(3G) — like a little echo, a little mirror, a little "you're welcome." no date given, so we're timeless. ⭐👑

stay hydrated, check your internalFormat, and remember: GL_TEXTURE_3D or it didn't happen. 💖

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