[sldev] Texture caching

[alissa_sabre at yahoo.co.jp]

Steve,

> 1. Anyone looking at texture caching, be sure to keep up with the latest 
> code drops because I have been rewriting that system in "First Look" 
> (which is now in the main source branch) and will be releasing it very soon.

That's the problem.  New source taballs appear every three days, with
significant changes on some _hot_ parts, but there are almost no
comments, change log, explanations at all.  It is almost impossible
for open source community (i.e., developpers not getting paid by LL)
to follow the changes.  We need to know the idea behind changes on
time.

... But I believe this criticism should go to Rob, not you.  You may
be another victim of the current collaboration scheme in that you
can't make use of open source developpers' effort to do your job
easier and quicker...

Sorry for wondering out.  Let's discuss texture caching.

> caching textures to disk mostly 
> just saves on network bandwidth.

And to reduce the server load, I guess.

> Decoding the textures takes quite a bit longer.

Why don't you cache decoded textures on disk?  I believe typical PC
compatible with SL viewer has more free disk space than 1GB.  I
understand that current VFS mechanism has some difficulty to handle a
lot of small data.  However, decoded textures are larger than their
compressed forms, and the number of objects doesn't change.  (I assume
compressed and decoded textures are stores as one object.  It should
be easy because the viewer can calculate the size of the decoded
texture from the header.)

Storing decoded textures on disk and load them as needed will reduce
the viewer CPU load when a lot of textures are required.

> However, each texture carries additional 
> system RAM and CPU overhead, so tracking tens of thousands of textures 
> is problematic in itself.

Storing decoded texture with its compressed form on disk will add no
RAM/CPU overhead.
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