BOCCARA Michael (MICHAEL.BOCCARA++at++siege.aerospatiale.fr)
Wed, 27 Nov 1996 18:09:30 +0100
I have a quite general question.
What would you propose to access to double precision for graphics concern ?
We are making space simulations with Performer 2.0 on an Onyx RE2.
According to the Performer Programming Guide, the graphic subsystem does only
support floating precision, not double.
The problem is that in space simulations, we have very important differences
of scale between object, for example between a spacecraft and the Earth.
So if we want to be able to see both a flying spacecraft in Space, and the
Earth, we have to set a very high ratio between Near and Far clipping planes,
that causes flickering in float precision.
Moreover, we have the same problem of precision concerning 3D positionning of
objects. Indeed, we need a precision of about 0.1 meter for an object which
is positionned at about 10000 kilometers from the Earth's center. We dont
have this precision with float variables, and so the result is a kind of
shiverring of objects.
The solution would be to work in double precision for graphics system, which
does not seem to be permitted.
Does someone have a trick to play with those problem of floating/double
precision ?
Does the Infinite Reality graphics support double precision ?
Thanks for your replies,
Kind regards,
Michael Boccara
Software Engineer
Aerospatiale, France
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