Would MoI be a good alternative to SubD modeling for game props?

 From:  Michael Gibson
5571.4 In reply to 5571.1 
Hi Tim, yes NURBS modeling is usually a much more natural fit for hard surface modeling than sub-d modeling.

With NURBS modeling you're able to use cutting and boolean operations as a primary way of building things, and this makes it pretty straightforward for construction of a lot of man-made type objects that are constructed by having some piece of stock that then has holes drilled in it and pieces cut off to form the final shape.

Basically the strong area of NURBS modeling is when you are able to form a lot of your model by focusing on creating 2D blueprint like curves and then using those curves directly, some for constructing base objects (like extrusion/revolving/sweeping), and then other curves used directly as cutting objects to drill holes or slice off ends of things. Many types of mechanical objects are well defined by 2D profile curves and fit with this method of modeling.

Organic shapes like monsters, characters, and faces are very different - they are a bad fit for this technique because they are not primarily __defined__ by 2D profiles, a 2D profile of a face for example does not "define" the face, it only captures the face at one single angle and it's rapidly changing in shape as you move away from that silhouette. So when there is not any 2D nature with the objects involved sub-d modeling tends to be a much better fit for that.

There are some kinds of models that are in a bit of a gray area which are semi-profile-driven but also kind of organic, sometimes vehicles can end up in this sort of gray area where it might not quite fit in either bucket exactly.

But for a lot of props and hand-held objects and things like that, NURBS should work quite well for those kinds of things.

It tends to be quick to work in 2D and when you're able to construct large sections of your model by a small number of 2D curves that's when you can become very productive and time efficient with NURBS modeling. That's specifically where it really shines and has its greatest strength.

It is a very different approach than sub-d modeling though and there are some kinds of habits from sub-d modeling that are not productive to try and replicate in NURBS.

To get some more ideas on some of these things, I'd recommend watching the video tutorials that are here as a good overview of the techniques involved:

Those walk through step-by-step with creating a few simple models and you can see how big chunks of the model are formed by only drawing and editing a small number of 2D curves.

And also check out here for some links to discussions and general tips for people who are coming from a sub-d / poly modeling background:

Probably the biggest difference from sub-d modeling is that with NURBS modeling you want to be using booleans as a primary way of building the model, ideally with a lot of just 2D curves involved.

Often I see poly modeling people try to build a "scaffolding" of mainly 3D curves and then trying to fill that in with little patches by doing a lot of sweeps or Network surfaces - that technique can be used for a type of organic modeling using NURBS but if you're doing a model that requires that it is kind of a red flag that you may have been better off using sub-d for that model anyway.

Another general problem that I see from sub-d modelers is trying to build surfaces directly to some kind of complex boundary. When Booleans are one of the primary tools to work with you often want to construct some initially more simplified and extended shape and then use Booleans or trimming to slice off chunks of that simple shape and form some of the final edges by intersections or cutting rather than directly drawing them. If you have hand drawn every single 3D edge in your final model rather than having many of them generated as intersections or cuts then you're not really using the NURBS toolset to its full advantage.

Hope these tips help! Check out the links above for a bunch of other similar kinds of discussion.

I would think MoI should be a good fit for you from what you have described though, basically MoI's primary reason for existence is to give artists who do not have a big mechanical engineering background to be able to make use of a NURBS toolset for models where that is a good fit which is mostly mechanical type models.

Like others mentioned above, you also might be able to use direct output from MoI for several kinds of cases rather than always doing retopo - do you always need to provide Unity with quad sub-d surfaces?

- Michael