Re: Texture paging on Impacts
Guy Russell (guyr++at++thoth.engr.sgi.com)
Mon, 22 Jul 1996 19:23:55 -0700
Hi Chris,
The Impact texture manager will perform texture save/restore for you
automatically and in the fastest download path, however it is not
deterministic. I am not sure exactly what issues you will be trying to solve
with texture paging. If you can get away with the texture manager doing it for
you that is the easiest path. If you have to control the downloads yourself,
then you will want to use glCopyTexSubImage2DEXT to manage the downloads. See
the man page for more details. Another possible solution is to use texture LOD
extensions to minimize the amount of texture required during a given frame.
See the glTexParameter man page for details on GL_TEXTURE_MIN_LOD_SGIS and
GL_TEXTURE_MAX_LOD_SGIS. Also make sure that your textures are sorted and
downloaded with 4 component textures first, 3 component textures second, 2
component textures third and 1 component textxtures last. If you can sacrifice
some image quality for performance, use 4 bit per component textures instead of
8 bit or 5551. Also, if you can convert RGB textures to luminance/intensity
textures with the color coming from the base poly, you will be able to reduce
your texture footprint dramatically.
I know that these suggestions are not the right answer for all
applications and we are working on some example code for texture paging on
Impacts. I am not sure when the example code will be available, probably a
couple of months, but as soon as it is I will announce it here and make it
available via ftp. Also, there are some Performer people who have been taking
IR demos and making them run on Impact. I am not sure, but I think that there
is one that does texture paging very fast.
Hope that helps,
Guy
--
Guy Russell
Member of the Technical Staff Silicon Graphics Inc.
Email:guyr++at++engr.sgi.com 2011 N. Shoreline Blvd. M/S 2U-923
Phone:(415)933-6113 Mountain View CA 94043
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