From: Jon M. Taylor <taylorj@ecs.csus.edu>
  To  : ggi-develop@eskimo.com
  Date: Wed, 19 Aug 1998 17:36:48 -0700 (PDT)

Re: LibGGI3D RFC

On Thu, 20 Aug 1998, Olivier Galibert wrote:

> On Wed, Aug 19, 1998 at 03:50:34PM -0700, Jon M. Taylor wrote:
> > 	KGI drivers should support whatever the hardware supports.  If the
> > hardware supports triangle sets, so should the KGI driver.
> 
> Hmmm, may I  amend this sentence?  I'd  rewrite it as "The  KGI driver
> should  support whatever  the  hardware supports   and  that cannot be
> handled safely and efficiently in userspace".  Do you agree?

	Pretty much.  At a certain level, efficiency == kernel bloat, but
this can be dotten around with a good command batching system.

> SGI hardware needs almost no kernel support.

	That is because it is designed properly. 

> > 	Backface culling should be done to the triangle sets (which
> > presumably representing polyhedra in this case) before sending them to
> > LibGGI3D for rendering.
> 
> What if the hardware itself does backface culling ?

	Then you skip the culling in software. 

> Or maybe we need another library to  abstract the geometry engine part
> of modern hardware?

	Yeah.  This sort of higher-level preprocessing should be done by
another library that sits on top of LibGGI3D.  LibGGI3Dworld is my name
for this mythical library.  It would tesellate polyhedra and surfaces into
triangles/triangle sets, clip to a view volume, do HSR, do backface
culling, do z-order sorting, etc.  

Jon 

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