From: Olivier Galibert <galibert@pobox.com>
  To  : ggi-develop@eskimo.com
  Date: Thu, 20 Aug 1998 03:20:31 +0200

Re: LibGGI3D RFC

On Wed, Aug 19, 1998 at 05:49:51PM -0700, Jon M. Taylor wrote:
> > Another  use of 3D  cards here (french CS research  center)  is to use
> > them  to  compute  the  visibility factors in   a scene  for radiosity
> > computing by having  the  hardware render   the scene without   lights
> > effects,  encoding each patch with  a unique color,  and then transfer
> > back the picture and count the pixels.  I guess it will be possible to
> > do that with libggi3d for  the rendering and  libggi2d to get back the
> > result?
> 
> 	Sure.  Write a modified radiosity-without-lights shader (probably
> it would do everything in greyscale) and then draw each patch through the
> shader and then through another shader which applied a color filter to the
> greyscale patch before redering it to the final display target.  Is that
> what you were looking for?

Nope.  You have   to get the  picture  back in  memory outside of  ggi
(OpenGL in their case, but anyway) and  count colors there (the number
of pixels of a given color is directly  proportionnal to the amount of
energy exchanged between the two patches).  You then use these results
in an equation system solver.

  OG.