Re: [Algorithms] terrain texturing

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

On Jan 15, 2001 at 09:32 +0100, Timo Heister wrote:
> 
> sorry, my target isn't geforce2+. I think i will use unique
> texturing. each texture is generated on-the-fly in software when
> needed. Then i'll add some detailmap to increase the detail around the
> camera.
> These techniques you and John descibe are very interesting but not
> suited for my needs.
> Which terrain-algo would you choose when targetting systems with tnt1
> or better?
> Algos that come into my mind:
> a) split-only-roam
> b) quadtree
> c) terrain mip-mapping (also kewl for geforce)
> 
> what do you think about c) ?
> I only read the paper and saw one implementation which suffers from
> heavy popping, but a) and b) seem to be hardware-unfriendly and
> cpu-dependant.

Soul Ride uses a system that sounds similar to what you're talking
about: unique texturing, rendered by software and then downloaded into
a texture cache.  The rendering/downloading hurts, especially on
TNT-level hardware, but it is feasible.

The way I see it, the algorithm used for meshing and the algorithm
used for texturing can/should be fairly independent of each other, so
the roam/quadtree/static discussion is a separate question.

I agree with you that texturing is really important for getting good
results with a terrain engine, probably more important than geometric
LOD in these days of fast hardware.  John R's description and
screenshots are very generous and should give you good ideas to keep
you busy for a while.  Combining his comments with my own experience,
I would distill the message down to a few bullet points:

* hi-res unique texturing with hi-res unique lighting looks great.

* you can't reasonably fit the full-resolution textures you need in
texture RAM all at once (e.g. in John's case 8192m x 8192m -->
64Mtexels), however, for any given viewpoint, most of the terrain is
far away and so can use a lower res version.  So you need some sort of
texture cache, and you need to be able to load/generate mip-mapped
versions of your texture tiles.

* detail rules, but RAM is limited... if you're serious, you need to
get into paging and/or compression.  Detail overlays, tiling,
splatting, procedural texturing etc can all be thought of as
compression techniques in some sense.

Those are the principles, the rest is just a bunch of minor
details... :)

-- 
Thatcher Ulrich <tu...@tu...>
==  Soul Ride -- pure snowboarding for the PC -- http://soulride.com
==  real-world terrain -- physics-based gameplay -- no view limits