Nurbs

rwaprogrammers · Post by **rwaprogrammers** » Tue Jan 17, 2006 2:48 am

Is there any way to export nurb curves and surfaces to ogre without using tools like convert to polygons. We've looked around to see if we can read something about nurbs in ogre. We do believe that you don't support nurbs or are we mistaken? if so how can we export them to ogre from any 3d api. if possible... but i believe that it can't be done? This is a BIG NOOB question.

Post by **xavier** » Tue Jan 17, 2006 2:51 am

Ogre does not support NURBS directly. You have to tesselate your patches first.

See the Downloads section on the site for all of the Ogre exporters available.

rwaprogrammers · Post by **rwaprogrammers** » Tue Jan 17, 2006 3:06 am

if we tesselate its like using the convert to polygons tool and for some of our models it destorys it. in fact its the same last i checked with the art dev team

Kentamanos · Post by **Kentamanos** » Tue Jan 17, 2006 3:11 am

The problem is NURBs are not really suited for real time, and in the end they need to be tessellated somewhere in order to get them displayed. It makes more sense to tessellate them in an offline tool than it does to do it in real time.

rwaprogrammers · Post by **rwaprogrammers** » Tue Jan 17, 2006 3:16 am

so nurbs are an absolute NO lol

hmm... are there any excellent tools to tesselate nurbs and not absolutly destroy them? if so please post otherwise its more work for the art team.

Kentamanos · Post by **Kentamanos** » Tue Jan 17, 2006 3:23 am

Well I know that in XSI, there are ways to convert geometry (subdivision surfaces at least, I imagine NURBs as well) into polygons. I expect that you'd find this in any major tool though and it's not really something unique to XSI. I'd have them check to see if the modelling tools they're using support it. You could also consider using normal maps generated by the NURBs versions too to make the polygon versions look better (since you already have a "hi res" model).

This is why modeling for games is an entirely different art form by the way. I think it's a lot easier to throw some complicated geometry together (NURBs or subdivision surfaces) than it is to create "low poly" geometry. That's not to say that just because I have access to NURBs or sub-d's that I can make anything look good at all

.

Rixeh · Post by **Rixeh** » Tue Jan 17, 2006 5:41 pm

If you're using Maya you can convert NURBS to Polys by tesellating by spans - each span will get converted into a face. ie: a 10x10 patch becomes a 100-face polygon. But you'll lose the curves inherent with NURBS, so you'll probably want to soften the normals.

Post by **jacmoe** » Tue Jan 17, 2006 6:14 pm

I believe that in Blender it is a simple command to turn a nurbs based model into a vertex one.
(Sorry about my terminology)

sgrgc · Post by **sgrgc** » Tue Jan 17, 2006 7:38 pm

AFAIK any modeller that supports nurbs will also support nurbs to mesh

Numsgil · Post by **Numsgil** » Sat Feb 04, 2006 8:37 pm

The problem is NURBs are not really suited for real time, and in the end they need to be tessellated somewhere in order to get them displayed. It makes more sense to tessellate them in an offline tool than it does to do it in real time.

This may seem a little off topic of me...

When I saw the Spore demo (the new Maxis game coming out sometime in the next year or so) the creature editor seemed to me to be using NURBS to let the user modify creature topology. At least, if it's not NURBS I'd be highly surprised.

Do you think they then tesselate the model when the user is done, saving the NURBS model for later editing, or maybe they found some way to display their NURBS without tesselation, or...

I assumed (I don't know much about NURBS) that they were just displaying NURBS instead of polygons, but I may have been a bit naive.

Post by **xavier** » Sat Feb 04, 2006 8:40 pm

Commodity graphics hardware deals only in triangles, period. They would have to be tesselating it at some point in order to show it using a graphics accelerator. This is no different than a typical 3D modelling tool using any number of curve- or patch-based methods, which then have to be tesselated into triangles later.