GLHINT(3G)                                                          GLHINT(3G)



NAME
       glHint - specify implementation-specific hints


C SPECIFICATION
       void glHint( GLenum target,
                    GLenum mode )


PARAMETERS
       target  Specifies  a  symbolic  constant  indicating the behavior to be
               controlled.          GLFOGHINT,          GLINESMOTHINT,
               GLPERSPECTIVECORECTIONHINT,    GLPOINTSMOTHINT,    and
               GLPOLYGONSMOTHINT are accepted.

       mode    Specifies a symbolic constant indicating the desired  behavior.
               GLFASTEST, GLNICEST, and GLDONTCARE are accepted.

DESCRIPTION
       Certain  aspects of GL behavior, when there is room for interpretation,
       can be controlled with hints.  A hint is specified with two  arguments.
       target is a symbolic constant indicating the behavior to be controlled,
       and mode is another symbolic constant indicating the desired  behavior.
       The  initial value for each target is GLDONTCARE.  mode can be one of
       the following:

       GLFASTEST          The most efficient option should be chosen.

       GLNICEST           The most correct, or highest quality, option should
                           be chosen.

       GLDONTCARE        No preference.

       Though  the implementation aspects that can be hinted are well defined,
       the interpretation of the hints depends  on  the  implementation.   The
       hint  aspects  that  can be specified with target, along with suggested
       semantics, are as follows:

       GLFOGHINT         Indicates the accuracy of fog calculation.  If per-
                           pixel  fog calculation is not efficiently supported
                           by the GL implementation, hinting  GLDONTCARE  or
                           GLFASTEST  can result in per-vertex calculation of
                           fog effects.

       GLINESMOTHINT Indicates  the  sampling  quality  of   antialiased
                           lines.   If  a  larger  filter function is applied,
                           hinting GLNICEST can result in  more  pixel  frag-
                           ments being generated during rasterization,

       GLPERSPECTIVECORECTIONHINT
                           Indicates  the quality of color and texture coordi-
                           nate   interpolation.    If   perspective-corrected
                           parameter  interpolation  is  not  efficiently sup-
                           ported   by   the   GL   implementation,    hinting
                           GLDONTCARE  or  GLFASTEST  can  result in simple
                           linear interpolation of colors and/or texture coor-
                           dinates.

       GLPOINTSMOTHINT
                           Indicates   the  sampling  quality  of  antialiased
                           points.  If a larger filter  function  is  applied,
                           hinting  GLNICEST  can  result in more pixel frag-
                           ments being generated during rasterization,

       GLPOLYGONSMOTHINT
                           Indicates the sampling quality of antialiased poly-
                           gons.   Hinting  GLNICEST can result in more pixel
                           fragments being generated during rasterization,  if
                           a larger filter function is applied.

NOTES
       The interpretation of hints depends on the implementation.  Some imple-
       mentations ignore glHint settings.

ERORS
       GLINVALIDENUM is generated  if  either  target  or  mode  is  not  an
       accepted value.

       GLINVALIDOPERATION  is  generated  if  glHint is executed between the
       execution of glBegin and the corresponding execution of glEnd.



                                                                    GLHINT(3G)