fglpixeltexgenparameter(3G)

NAME
     fglPixelTexGenParameterfSGIS, fglPixelTexGenParameteriSGIS,
     fglPixelTexGenParameterfvSGIS, fglPixelTexGenParameterivSGIS - affects
     the generation of texture coordinates in pixel operations


FORTRAN SPECIFICATION
     SUBROUTINE fglPixelTexGenParameterfSGIS( INTEGER*4 pname,
                                              REAL*4 param )
     SUBROUTINE fglPixelTexGenParameteriSGIS( INTEGER*4 pname,
                                              INTEGER*4 param )


PARAMETERS
     pname   Specifies the symbolic name of the parameter to be set, which
             must be either GL_PIXEL_FRAGMENT_RGB_SOURCE_SGIS or
             GL_PIXEL_FRAGMENT_ALPHA_SOURCE_SGIS.

     param   Specifies a symbolic constant, which must be either
             GL_CURRENT_RASTER_COLOR or GL_PIXEL_GROUP_COLOR_SGIS.

FORTRAN SPECIFICATION
     SUBROUTINE fglPixelTexGenParameterfvSGIS( INTEGER*4 pname,
                                               CHARACTER*8 params )
     SUBROUTINE fglPixelTexGenParameterivSGIS( INTEGER*4 pname,
                                               CHARACTER*8 params )


PARAMETERS
     pname
          Specifies the symbolic name of the parameter to be set, which must
          be either GL_PIXEL_FRAGMENT_RGB_SOURCE_SGIS or
          GL_PIXEL_FRAGMENT_ALPHA_SOURCE_SGIS.

     params
          Specifies a pointer to an array where the value of pname is stored.
          The value must be either GL_CURRENT_RASTER_COLOR or
          GL_PIXEL_GROUP_COLOR_SGIS.


DESCRIPTION
     The pixel texture function is enabled by calling fglEnable and disabled
     by calling fglDisable with GL_PIXEL_TEXTURE_SGIS.  Pixel texture affects
     the result of fglDrawPixels and fglCopyPixels operations by converting
     color components into texture coordinates.  Because texture mapping is
     essentially a multidimensional table lookup, this conversion supports
     multidimensional color lookups for images.  Such multidimensional lookups
     can be used to implement very accurate color space conversions.

     When pixel texture is enabled, the red, green, blue, and alpha components
     are used to generate s, t, r, and q texture coordinates, respectively.
     If a valid texture has been defined, and texture-mapping enabled, these
     texture coordinates will produce, in effect, a function of the color
     components, which can then be blended with the original color components,
     according to the texture environment blend function.

     Texture coordinates can be generated from either the pixel color or the
     current raster position's color values.  The source of the red, green,
     and blue values can be selected separately from the source of the alpha
     values by calling fglPixelTexGenParameterSGIS with different values of
     pname:

     GL_PIXEL_FRAGMENT_RGB_SOURCE_SGIS
               params selects which red, green, and blue values are used to
               generate the s, t, and r texture coordinates.  If params is
               GL_PIXEL_GROUP_COLOR_SGIS then s, t, and r will be generated
               from the pixel color data.  If params is
               GL_CURRENT_RASTER_COLOR then s, t, and r will be generated from
               the current raster position color.  The default is
               GL_PIXEL_GROUP_COLOR_SGIS.

     GL_PIXEL_FRAGMENT_ALPHA_SOURCE_SGIS
               params selects which alpha values are used to generate the q
               texture coordinates.  If params is GL_PIXEL_GROUP_COLOR_SGIS
               then q will be generated from the pixel alpha data.  If params
               is GL_CURRENT_RASTER_COLOR then q will be generated from the
               current raster position alpha value.  The default is
               GL_PIXEL_GROUP_COLOR_SGIS.


ERRORS
     GL_INVALID_ENUM is generated when pname is not an accepted defined value.

     GL_INVALID_ENUM is generated when params is not an accepted defined
     value.

     GL_INVALID_OPERATION is generated if fglPixelTexGenParameterSGIS is
     executed between the execution of fglBegin and the execution of the
     corresponding fglEnd.

ASSOCIATED GETS
     fglGetPixelTexGenParameterSGIS
     fglIsEnabled with argument GL_PIXEL_TEXTURE_SGIS


MACHINE DEPENDENCIES
     fglPixelTexGenParameterSGIS is supported only on Octane2 VPro systems.

     Octane2 VPro systems support only the GL_PIXEL_GROUP_COLOR_SGIS mode for
     GL_PIXEL_FRAGMENT_RGB_SOURCE_SGIS and
     GL_PIXEL_FRAGMENT_ALPHA_SOURCE_SGIS.

SEE ALSO
     fglDisable, fglEnable, fglGetPixelTexGenParameterSGIS, fglIsEnabled