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GLUBUILD1DMIPMAPS()                                        GLUBUILD1DMIPMAPS()


NAME

       gluBuild1DMipmaps - builds a 1-D mipmap


C SPECIFICATION

       GLint gluBuild1DMipmaps( GLenum target,
                                GLint internalFormat,
                                GLsizei width,
                                GLenum format,
                                GLenum type,
                                const void *data )


PARAMETERS

       target          Specifies the target texture. Must be GL_TEXTURE_1D.

       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           Specifies the width, 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

       gluBuild1DMipmaps builds a series of prefiltered 1-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 of data is checked to see if it is 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 is exactly between powers of 2,
       then the copy of data will scale upwards.)  For example, if width is 57
       then a copy of data will scale up to 64 before mipmapping takes place.

       Then, proxy textures (see glTexImage1D) are used to determine if the
       implementation can fit the requested texture. If not, width is
       continually halved until it fits.

       Next, a series of mipmap levels is built by decimating a copy of data
       in half until size 1 is reached. At each level, each texel in the
       halved mipmap level is an average of the corresponding two texels in
       the larger mipmap level.

       glTexImage1D is called to load each of these mipmap levels.  Level 0 is
       a copy of data.  The highest level is log2(width).  For example, if
       width is 64 and the implementation can store a texture of this size,
       the following mipmap levels are built: 64x1, 32x1, 16x1, 8x1, 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 type. See the glDrawPixels reference page for a description
       of the acceptable values for data.


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 actually used at level 0.  (The width may not be equal to
       width since proxy textures might have scaled it to fit the
       implementation.)  Then the maximum level can be derived from the
       formula log2(width).


ERRORS

       GLU_INVALID_VALUE is returned if width is < 1.

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


SEE ALSO

       glDrawPixels, glTexImage1D, glTexImage2D, gluBuild2DMipmaps,
       gluErrorString, gluScaleImage

                                                           GLUBUILD1DMIPMAPS()

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