Index for Section 3

Alphabetical listing for G

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gluBuild2DMipmaps()
NAME
  gluBuild2DMipmaps - builds a 2-D mipmap

SYNOPSIS
  GLint gluBuild2DMipmaps(
	  GLenum target,
	  GLint internalFormat,
	  GLsizei width,
	  GLsizei height,
	  GLenum format,
	  GLenum type,
	  const void *data );

PARAMETERS
  target
      Specifies the target texture. Must be GL_TEXTURE_2D.

  internalFormat
      Requests the internal storage format of the texture image. Must be 1,
      2, 3, or 4 or one of the following 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, height
      Specifies the width and height, respectively, in pixels of the texture
      image.

  format
      Specifies the format of the pixel data. Must be one of: GL_COLOR_INDEX,
      GL_RED, GL_GREEN, GL_BLUE, GL_ALPHA, GL_RGB, GL_RGBA, GL_LUMINANCE, and
      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, or GL_FLOAT.

  data
      Specifies a pointer to the image data in memory.

DESCRIPTION
  gluBuild2DMipmaps() builds a series of prefiltered 2-D texture maps of
  decreasing resolutions called a mipmap. This is used for the antialiasing
  of texture mapped primitives.

  A return value of 0 indicates success, otherwise a GLU error code is
  returned (see gluErrorString()).

  Initially, the width and height of data are checked to see if they are a
  power of two. If not, a copy of data (not data), is scaled up or down to
  the nearest power of two. This copy will be used for subsequent mipmapping
  operations described below. (If width or height is exactly between powers
  of 2, then the copy of data will scale upwards.) For example, if width is
  57 and height is 23 then a copy of data will scale up to 64 and down to 16,
  respectively, before mipmapping takes place.

  Then, proxy textures (see glTexImage2D()) 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
  glGetIntegerv() with the argument GL_MAX_TEXTURE_SIZE.)

  Next, a series of mipmap levels is built by decimating a copy of data in
  half along both dimensions until size 1x1 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 x 1 or 1 x N configuration.  Here,
  two texels are averaged instead.)

  glTexImage2D() is called to load each of these mipmap levels. Level 0 is a
  copy of data. The highest level is log[2](max(width,height)). For example,
  if width is 64 and height is 16 and the implementation can store a texture
  of this size, the following mipmap levels are built: 64x16, 32x8, 16x4,
  8x2, 4x1, 2x1 and 1x1. These correspond to levels 0 through 6,
  respectively.

  See the glTexImage1D() reference page for a description of the acceptable
  values for format. See the glDrawPixels() reference page for a description
  of the acceptable values for type.

NOTES
  Note that there is no direct way of querying the maximum level. This can be
  derived indirectly via glGetTexLevelParameter().  First, query for the
  width & height actually used at level 0. (The width & height may not be
  equal to width & height respectively since proxy textures might have scaled
  them to fit the implementation.) Then the maximum level can be derived from
  the formula log[2](max(width,height)).

ERRORS
  GLU_INVALID_VALUE is returned if width or height are < 1.

  GLU_INVALID_ENUM is returned if internalFormat, format or type are not
  legal.

SEE ALSO
  glDrawPixels(3), glTexImage1D(3), glTexImage2D(3), gluBuild1DMipmaps(3),
  gluErrorString(3), gluScaleImage(3)

Index for Section 3

Alphabetical listing for G

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