NURBS for Environments?

[mistan]

I know that NURBS is bad for animations, but would it not be possible/feasible for next gen games to use NURBS for the environments since they will mostly be static.
Unless we're talking about destructible environments but wouldnt there be a work around for that?
Just wondering.. 8)
It's been on my mind since it was announced for PSP.

 

[Farid]

Evolution Studios WRC, and EA SSX do use NURBS for the environement.

 

[Shifty Geezer]

NURBS roads would probably make the most sense. Certainly in the UK roads aren't constructed from short straight pieces

 

[nAo]

Evolution Studios WRC, and EA SSX do use NURBS for the environement.

Dunno about WRC, but SSX uses bezier patches AFAIK.
Regarding the main question: is indeed possible to use NURBS for enviroments, but I don't think it would the right move to do, in the general case you'd better use something more advanced and flexible as subdivision surfaces (run time evualation/tesselation could be even faster with SS..)

 

[London Geezer]

Also, we want destructible environments, right?

Nurbs/Bezier breaking = pain.

 

[Guden Oden]

Also, we want destructible environments, right?

In a Mad Max-like driving game we most certainly would... I've wanted a decent Rock n Roll Racing followup practically since I played the original back on the SNES!

 

[MfA]

Anything you can describe with NURBS you can describe with rational bezier surfaces too, and those are easier to render ... NURBS are for modeling, and they arent the greatest for that either.

 

[Simon F]

Anything you can describe with NURBS you can describe with rational bezier surfaces too, and those are easier to render ... NURBS are for modeling, and they arent the greatest for that either.

Well said.

 

[Shifty Geezer]

I think 'NURBS' is used as a common term for HOS, and don't specifically (in most people's use) pertain to a particular way of modelling/representing curve data.

 

[Farid]

Dunno about WRC, but SSX uses bezier patches AFAIK.

I think you're right about that, but as Shifty pointed out, I just use loosely the term NURBS.

 

[London Geezer]

In the end they're all rendered as polygons so it's not like they're "free" curved suraces.
What might be saved is the information needed to store a NURBS model compared to a very high polygon model - Disc and RAM space. Not sure what the extent of the saving is, i seem to remember hearing that NURBS doesn't save you a whole lot of space compared to a decently high-polygon mesh anyway so they're not worth the hassle. Maybe Faf knows.

In the end i say, NURBS were tried and left to die a loooong time ago, and there must be a reason.

 

[mistan]

I also am using it loosely.
Thanks for the comments

 

[Sonic]

NURBS is still used today in the CG field. If you want good results with it then Rhino is a good bet. Even with that I am no longer fond of it as the things it can do can be done better with others.

Subdivisions are really great.

 

[Shifty Geezer]

SDS are the future (if nothing else comes along!). It's what the modelling apps mostly use and they can be very economical memory-wise. The key strength with HOS surfaces isn't necessarily mem-savings (which can be very high depending on complexity) but the degree of adaptive rendering. They basically have 'infinite resolution' that you tesselate to output quality, meaning easy LOD with the same source detail as close-up models. On the PC, HOS would allow more complex models on better hardware, using the same art assets as low-end machines, without the artists needing to worry about poly counts too much (though they will have to factor in low-level tesselation looking pretty manky if they're not careful).

The major drawback is processing requirements, plus interpolation/tesselation errors. I'm not sure how these are a concern in a realtime environment though.

Am I right in thinking OGL 2.0 has HOS support, and Collada too? Are we now in a position where, if someone writes an interpolator or other rasterizer, artists can directly use their HOS development models in game?

 

[Simon F]

I think 'NURBS' is used as a common term for HOS, and don't specifically (in most people's use) pertain to a particular way of modelling/representing curve data.

I'd have to disagree with that. "NURBS" are a specific modelling method and, in text books, they are usually introduced after other HOS methods. (Of course, these often form the basic building block for rendering NURBS).

 

[Shifty Geezer]

Amongst those not in the know, NURBS is talked of in realtime (games) as non-triangle surfaces mostly. If an object is a smoothly rendered HOS it's likely it'll be called a NURBS surface by most without any knowledge of how it's actually done. In essence people's education goes so far as to know NURBS = 'not triangles'.

 

[Laa-Yosh]

NURBS makes the most sense for circular objects, like a car's wheels. Imagine that we'd want some rounded edges too, and a nice smooth appearence from a closeup view. That'd take about 40-60 radial segments for a polygonal wheel, which should then be multiplied at least 10-15 times for the additional segments for the rounded edges; and then doubled up for triangles. So it's 600-1800 polygons for a single wheel only, and then there are exhaust pipes, wheelarchs, and who nows what.

With NURBS or some other sort of higher order surface, on the other hand, you could do it with 80-100 control vertices and that's all. The problems would be lack of unwrapable UVs (1 texture per surface that gets distorted) and maybe the quadratic structure (Carmack seemed to hate that).

 

[Simon F]

The problems would be lack of unwrapable UVs (1 texture per surface that gets distorted)

Why are they any different to triangle meshes in that regard? Can't you just treat U&V as an extra set of dimensions? I've done this with Beziers and Uniform BSplines.

and maybe the quadratic structure (Carmack seemed to hate that).

Quadratic? Hardly. IIRC Carmack used quadratic Beziers at one stage, but there's no need to limit yourself to that order with either Beziers or NURBS.

OH!! Did you mean rectangular when you wrote "quadratic"? In that case, yes, the topology can be a pain, which is why subdivision surfaces are becoming popular.

 

[Laa-Yosh]

Yeah, I was talking about topology Rectangular should be a better word for it, although we modelers usually talk about 'quad polygons'.
NURBS is bicubic in mathematical terms though, and not biquadratic, right?

 

[Barbarian]

I would say bezier patches are a more realistic solution rather than NURBS, mostly because it seems bezier patch support is slowly trickling into HW (PSP, Xenos?).
The memory saving can be significant if bezier patches are used for what they are good at - rectangular, curvy things - roads, pillars, wheels etc.
The True Crime series use bezier patches, and I can assure you the current virtual city size would not be possible without bezier patches.
Not to mention bezier patches render beautifully on the PS2's VU with 'free' LOD.