Jenny Zhao (zhz++at++dandan.asd.sgi.com)
Mon, 26 Aug 1996 14:48:17 -0700
> > My concern is in the first frame after each time
> > the pfSwitch is toggled. In this frame time, APP and DRAW would get the
same
> > set of gsets, which APP gets them because they are associated to the
> pfTerrain
> > it has newly received due the switch toggle, and DRAW would get at least
some
> > of them which are passed down from CULL that worked on them in the previous
> > frame (when APP was working on the other set of gsets and the associated
> > pfTerrain in its last pass). It seems to me that it is the consequence of
> > "double-buffering pfSwitch" node used in a three stage pipeline. I hope I
> > described it clearly.
>
> I see what you mean. The APP doesn't know about the pfSwitch setting so it
> could potentially conflict with the DRAW. The way it's is setup in the demo,
> starting from frame 0, the conflict would happen in frames 8 and 9.
>
> But! the evaluation actually has two sub tasks: evaluating the potential
> triangles and "weaving" the final mesh. The weave task actually populates
the
> geosets and it runs to completion in a single frame. There is no incremental
> conflicts. Note that this is an evaluation bottle neck and limits
scalability.
> Still this demo has handled much of northern california (from 100m dted)
with
> clipmapping (30 meter texels as I recall) at 60Hz on a properly configured
iR.
>
> PS: Improved mechanisms and algorithms are being developed, rest assured.
>
> Regards.
> --
Marcus is right. the last stage of the TerrainEvaluation is the
geoset generation, and before that, the terrain does
the traversal of the database.
also we overlapped the beginning of the TerrainEvaluation and
the DRAW, the real writing doesn't really happen until
3 frames later. that is why the demo
worked safely.
the new release of performer will have a new asychronize evaluation
which will make the terrain evaluation process independent of
the performer main process.
> ____ ___ ____ _ Marcus Barnes, Member Technical Staff
> / __ `__ \/ __ `( ) MultiGen Inc. 550 S. Winchester Blvd. STE 500
> / / / / / / /_/ / / San Jose CA 95128 WEB: http://www.multigen.com
> /_/ /_/ /_/\__, /_/ PH:1-408-556-2654 FX:1-408-261-4102
> /____/ EMAIL: marcus++at++multigen.com
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>-- End of excerpt from Marcus Barnes
--
Jenny Zhao zhz++at++asd.sgi.com 415 933-5091 (Voice) 415 965-2658 (Fax) Silicon Graphics - IRIS Performer ======================================================================= List Archives, FAQ, FTP: http://www.sgi.com/Technology/Performer/ Submissions: info-performer++at++sgi.com Admin. requests: info-performer-request++at++sgi.com
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