Angus Dorbie (dorbie++at++sgi.com)
Wed, 01 Jul 1998 12:24:52 -0700
So what's difficult about what I've described?
I implemented this approach in half a day for a Performer
talk on the subject
It's even easier when you consider that in many
simulators as packets arrive the conversion can
be made before they even touch your application
software.
1) Subtract double precision eye xyz from every double
precision object position xyz and cast to float.
2) Subtract double precision eye xyz from every double
precision light source position xyz and cast to float.
3) Keep eye at the Origin.
4) Perform -eye matrix translation of OpenGL
rendering code not in scene graph (actually best to
keep local and manage some lower translation nubmer)
Stage 4 ofcourse is optional depending on the app, it's
not really performers fault.
This seems pretty straighforward to me. It's extremely
easy and trivial once you understand the problem.
You have to simulate /animate etc in double
precision but that's a host/application issue and an
obvious staple of an app even if the graphics pipe did
all the graphics in double precision.
Even if you only do the above without double precision
app, it would save on the roundoff Steve mentioned.
Cheers,Angus.
-- "Only the mediocre are always at their best." -- Jean GiraudouxFor advanced 3D graphics Performer + OpenGL based examples and tutors: http://www.dorbie.com/ ======================================================================= 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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