GLUBUILD1DMIPMAPLEVELS(3G)

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

GLUBUILD1DMIPMAPLEVELS 💖 (section 3G, the GLU girlies)

okay so bestie, we're in the GLU corner of the man pages, section 3G — this is gluBuild1DMipmapLevels(3G) and it's giving mipmap builder but you pick which levels ✨

✨ NAME ✨

gluBuild1DMipmapLevels — builds a subset of one-dimensional mipmap levels 🦋

🎀 C SPECIFICATION 🎀

GLint gluBuild1DMipmapLevels( GLenum target,
                              GLint internalFormat,
                              GLsizei width,
                              GLenum format,
                              GLenum type,
                              GLint level,
                              GLint base,
                              GLint max,
                              const void *data )

like. nine arguments. she's high maintenance and we love her for it 💅

🌸 PARAMETERS 🌸

  • target — which texture we're targeting, bestie. Must be GL_TEXTURE_1D.
  • internalFormat — this is what you're requesting for the internal storage of the texture image. Here's the tea tho: 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 the OpenGL implementation doesn't accept, you get an OpenGL error, periodt. The whole point of not checking at the GLU level is that OpenGL extensions can add new internal texture formats without needing a whole revision of the GLU implementation — iconic design moment tbh.

BUT: older implementations of GLU do check this value, and they'll 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.

  • width — the width in pixels of the texture image. This should be a power of 2. (should!! she said should 👀)
  • format — specifies the (the original page dropped a word right here, no cap — it's the format, iykyk) 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.
  • type — 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. so many. she has range 💜
  • level — the mipmap level of the image data.
  • base — the minimum mipmap level to pass to glTexImage1D.
  • max — the maximum mipmap level to pass to glTexImage1D.
  • data — a pointer to the image data in memory. 🫶

💖 DESCRIPTION 💖

gluBuild1DMipmapLevels builds a subset of prefiltered one-dimensional texture maps of decreasing resolutions — that whole stack is called a mipmap. It's used for the antialiasing of texture mapped primitives. slay.

A return value of zero means success, bestie. Anything else? that's a GLU error code coming back at you (go see gluErrorString).

A series of mipmap levels from base to max gets built by decimating data in half until size 1×1 is reached. At each level, every texel in the halved mipmap level is an average of the corresponding two texels in the larger mipmap level. Then glTexImage1D 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 (again: see gluErrorString) and nothing is loaded. nothing. nada. 💀

For example, if level is 2 and width is 16, the following levels are possible: 16×1, 8×1, 4×1, 2×1, 1×1. These correspond to levels 2 through 6 respectively. If base is 3 and max is 5, then only mipmap levels 8×1, 4×1 and 2×1 are loaded. But if max is 7? then an error is returned and nothing is loaded, because max is larger than the highest mipmap level which is, in this case, 6. rude of you honestly 🙈

The highest mipmap level can be derived from the formula:

log2(width2level)

See the glTexImage1D reference page for a description of the acceptable values for type parameter. See the glDrawPixels reference page for a description of the acceptable values for level parameter.

👑 NOTES 👑

  • gluBuild1DMipmapLevels is only available if the GLU version is 1.3 or greater. check your version bestie, don't get caught out.
  • 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 ⭐

the vibe check fails and these come back at you:

  • 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 is < 1.
  • GLU_INVALID_ENUM is returned if internalFormat, format, or type are 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.
like the amount of GLU_INVALID_OPERATION here is wild but it's all "your packed type doesn't match your format" energy. match them. please. 😭

🦋 SEE ALSO 🦋

glDrawPixels(3G), glTexImage1D(3G), glTexImage2D(3G), glTexImage3D(3G), gluBuild1DMipmaps(3G), gluBuild2DMipmaps(3G), gluBuild3DMipmaps(3G), gluErrorString(3G), glGetTexImage(3G), glGetTexLevelParameter(3G), gluBuild2DMipmapLevels(3G), gluBuild3DMipmapLevels(3G)

and that's the whole page, bestie 🎀 the footer at the bottom is literally just the page name again — GLUBUILD1DMIPMAPLEVELS(3G) — which is the cutest possible way of saying "yeah, this is the GLU manual, section 3G, that's the whole source/version situation". go build some mipmaps. ily. 💖✨🌸

📦 where this page comes from