Re: [Algorithms] terrain texturing

[Timo H. <Tim...@gm...>]

Hi Thatcher,

 Dienstag, 16. Januar 2001, you wrote:

> 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.

Does soul ride has a fully unique texturing approach? or are some
textures used a few times? (should be possible when displaying snow)
Anyway,I think i will give it a try.

> 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.

Thats right, but a few things are dependent, for example John's Algo
uses detail-polys to blend the textures which has a connection to the
texture generation. When i don't have to blend the textures i won't
need extra detail polys for blending ...
but you are right, perhaps i should start a new thread.

> 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.

Do not forget good lighting ...

>   John R's description and
> screenshots are very generous and should give you good ideas to keep
> you busy for a while.

Yep, it was really kind to tell us his secret algos. But i think my
engine won't be the future reference. It kindof helped me, but i'm not
sure if it works that good for current hardware.

>  Combining his comments with my own experience,
> I would distill the message down to a few bullet points:

that's nice ;)

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

right, i would even say, that one should consider lowering the
poly-count for more texture/lighting detail. With a few hundret polys
and large textures you can even build a few very nice moutains. (note
that i won't work as good with normal binary/.. trees because they
aren't as efficient)

> * 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.

The question is, if leaving a really low-resolution texture of the
whole terrain in texture-ram is a good idea. When you get near a quad
you can upload a larger version. what do you think? It perhaps depends
on how large your terrain is and where the far clipping-plane is.

> * 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.

right, has anyone any experience with texture-compression (s3tc,dds
...) ? How is the quality of the textures? How fast is the generation?
(when generating compressed textures in realtime)

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

The problem sometimes is in the detail !



CU, Timo

-- 
Timo Heister
    E-mail: Tim...@gm...
    ICQ:    <ask me>