Mark Aubin (aubin++at++mustang.engr.sgi.com)
Fri, 3 Sep 1999 11:05:00 -0700 (PDT)
The easiest way to think about this is that a cliptexture is a virtual
texture with maximum dimensions of 2^31 by 2^31. All your geometry
has s & t texture coordinates into this single virtual texture. Performer
is responsible for moving pieces of your clipmap database in and out
of the texture cache and updating the clipcenter so that you will
have the highest resolution available for geometry in your view.
What do you mean by "where it is"? Infinite Reality graphics are
the only place you will find cliptextures today.
All access to this special hardware is through OpenGL extensions, many
of which we don't give out any details on. Our design goal was to
enable the hardware through IRIS Performer. You would be very hard
pressed to get any cliptexture to work outside of IRIS Performer. But
it is possible. I don't know of anybody who has ever tried though.
My guess is that what you really want to be asking for is a global
texture capability to be supported by IRIS Performer. On Infinite
Reality hardware, it could use cliptextures. On non-IR hardware,
some other texture paging mechanism could be used.
By the way, years before we had Infinite Reality hardware, we were
showing terrain fly-overs of high-resolution geo-specific terrain,
thanks to our friends at CA&D (now Aechelon). This was done on
RE2 hardware with 4MB of texture memory using IRIS Performer and
custom paging software. No special hardware. But it was very,
very hard to do. Once we had IR hardware, they quickly abandoned
their custom stuff (and helped us work out the kinks in cliptextures).
--Mark Aubin
This archive was generated by hypermail 2.0b2 on Fri Sep 03 1999 - 11:05:14 PDT