Re: [Algorithms] ROAM

[Thatcher U. <tu...@tu...>]

On Nov 29, 2002 at 11:07 -0000, Tom Forsyth wrote:
> From: Pierre Terdiman [mailto:p.t...@wa...]
> > There was that thing called "clipmaps" in SIG97... IIRC the
> > texture was like 40 million * 20 million texels. Nice :)
> 
> Virtual texturing is a much cooler technology than clipmaps
> though. It's got finer granularity, is (oddly) easier to implement,
> and has a wider application.
> 
> Now we just have to wait for more than one IHV to implement it. It's
> not the new lensflare, but it is the new bumpmapping, in that it's
> cool tech, everyone agrees it's cool tech, but it'll take ten years
> after it was shown to work to get mainstream use :-)

If you can't wait that long, use quadtree tiling :).  There's an
example in the chunked LOD demo.  It's a coarse-grained method to
solve the same problem without using any hardware extensions.  Public
domain code at the usual place:

http://sourceforge.net/projects/tu-testbed

One interesting advantage of doing it this way is that I could use
JPEG compression on the textures, so a 32K x 32K texture that normally
would have consumed several GB uncompressed, or 512MB (using
conventional hardware compression @ 4 bits/texel), instead took
~150MB.  By the same token, it's a good framework for doing some
procedural stuff.  On the other hand there's the usual time/space
tradeoff to deal with decompression.

-- 
Thatcher Ulrich
http://tulrich.com