From: Jon M. Taylor <taylorj@ecs.csus.edu>
  To  : ggi-develop@eskimo.com
  Date: Thu, 20 Aug 1998 11:45:06 -0700 (PDT)

Re: LibGGI3D RFC

On Wed, 19 Aug 1998, teunis wrote:

> On Wed, 19 Aug 1998, Jon M. Taylor wrote:
> 
> > On Wed, 19 Aug 1998, teunis wrote:
> 
> [clip]
> 
> > > Now thinking about it:
> > > 	Coordinate clipping requires info about -all- present coordinates.
> > > 		(X,Y,Z[,W][,U,V[,U2,V2..]][colour])
> > > 	mayhaps we need to think about this further?  (don't know)
> > 
> > 	The higher layers could clip during tesellation, and as such
> > they'd be able to take all those coordinates into account.
> 
> Ah - so the only clipping libGGI3D would do would be?

	Render-side clipping. if anything. 

> I'm curious, as moving any of the X,Y[,Z] coordinates will affect the
> remainder of the coordinate list...

	For one triangle this shouldn't be a problem.  For a set, you do
what you can. 

> > > >  - I want clipping in libggi3d also.
> > > 
> > > See above...  and this requires also the camera info (view frustrum,etc)
> > > to be available....
> > 
> > 	Right. 
> 
> So how does this work?

	Attach it as a struct to the visual. 

> > 	Why not set up such caching systems as intermediate display
> > targets?  Drawing functions would render to the caching target, which
> > would do the appropriate cache lookups, flushing, updating, etc and then
> > render to the final target.  I would work the same way as other LibGGI
> > intermediat targets (tile, trueemu, palemu, etc).
> 
> 
> hmm...  Okay - makes sense.
> That means doing a 
> vis=ggiOpen("display-texture", [view options]);
> vis=ggiOpen("display-Zbuffer", ...);
> vis=ggiOpen("display-wbuffer", ...);
> 
> Yes?

	Yeah.  They you'd maybe use something like LIBGGI[3D?]_DISPLAY =
cache:[texture,zbuffer,...].  I dunno LibGGI *that* well yet. 

> Though there should be some kind of internal mechanism for handling
> display memory!  (so it doesn't get all fragmented and can be used
> effectively!)

	I guess the buffer system doesn't *have* to be in a target.  AAIK 
is isn't(?) in LibGGI2D.

Jon 

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