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       icetDrawFrame -- renders and composites a frame


       #include <GL/ice-t.h>

       void icetDrawFrame(void);


       Initiates a frame draw using the current OpenGL transformation matrices
       (modelview and projection).

       IceT may render an image, the tile display needs to be  defined  (using
       icetAddTile)   and   the  drawing  function  needs  to  be  set  (using
       icetDrawFunc).  The composite  strategy  may  also  optionally  be  set
       (using icetStrategy).

       If  ICET_DISPLAY is enabled, then the fully composited image is written
       back to the OpenGL framebuffer for display.  It  is  the  application's
       responsibility  to  synchronize  the  processes and swap front and back
       buffers. If the OpenGL background color is set to something other  than
       black,   ICET_DISPLAY_COLORED_BACKGROUND   should   also   be  enabled.
       Displaying  with  ICET_DISPLAY_COLORED_BACKGROUND   disabled   may   be
       slightly  faster  (depending  on  graphics  hardware) but can result in
       black rectangles in the background. If ICET_DISPLAY_INFLATE is  enabled
       and the size of the renderable window (determined by the current OpenGL
       viewport) is greater than that of the tile being  displayed,  then  the
       image  will  first  be `inflated' to the size of the actual display. If
       ICET_DISPLAY_INFLATE is disabled, the image is drawn  at  its  original
       resolution at the lower left corner of the display.

       The image remaining in the frame buffer is undefined if ICET_DISPLAY is
       disabled or the process is not displaying a tile.


               Raised if the drawing function has not been set.  Also  can  be
              raised  if  icetDrawFrame  is  called recursively, probably from
              within the drawing callback.

               Not enough memory left to hold intermittent frame  buffers  and
              other temporary data.




       If  compositing  with  color  blending  on,  the  image  returned  with
       icetGetColorBuffermay have values of $<R, G, B, A >= <0, 0, 0, 0  >$and
       the rest of the image may be blended with black rather than the correct
       background color.

       During compositing,  image  compression  is  employed  that  relies  on
       knowing  the  maximum  possible  value  in the z-buffer. Unfortunately,
       different rendering hardware can give different results for this value.
       IceT  tries  to  dermine this value up front by clearing the screen and
       reading the z-buffer value, but this test sometimes fails, resulting in
       a  classification  of background. The side effects of this are minimal,
       and IceT usually quickly fixes  the  problem  by  continually  checking
       depth values.


       Copyright (C)2003 Sandia Corporation

       Under the terms of Contract DE-AC04-94AL85000, there is a non-exclusive
       license for use of this work by or on behalf of  the  U.S.  Government.
       Redistribution  and  use  in  source  and binary forms, with or without
       modification, are permitted provided that this Notice and any statement
       of authorship are reproduced on all copies.

See Also

       icetResetTiles(3),          icetAddTile(3),         icetBoundingBox(3),
       icetBoundingVertices(3),       icetDrawFunc(3),        icetStrategy(3),
       icetGetColorBuffer(3), icetGetDepthBuffer(3)

IceT Reference                 February 14, 2008              icetDrawFrame(3)