> I think it might be a bit too much for Michael to do for V1... or V2 for that matter :S

:) I can definitely say that it's too much for V2 as well. There is still a lot of ground to cover for non-Sub-D NURBS modeling.

It will be quite a ways out before it will be possible for me to work on this type of hybrid functionality for MoI.


> Could you give me a hint where I might find some info on coding
> such a poly sweep function?

Well, some older names for 2-rail sweeping is "birail", so you might do some searching using that term.

"The NURBS Book", by Les Piegl and Wayne Tiller have a section on one-rail sweeping. They give a couple of references:

Sweep surfaces modelling via coordinate transformations and blending : http://portal.acm.org/citation.cfm?id=87207

V Akman, A Arslan, Sweeping with all graphical ingredients in a topological picturebook, Computers & Graphics 16(3): 273-281 (Fall 1992) [WOS]

Try searching scholar.google.com and ACM for papers about "sweeping".


I think the Hexagon modeler implements these kinds of features for polygon modeling, so you might look over there to see what they have done.

Are you expecting to do this sweep function on polygon line segments, or on curves? Doing it on polygon line segments will probably introduce a lot of different issues because one part of the sweeping function is usually a recursive adaptive fit to the rails, where you start with a coarser version of the sweep and continue to add in points to refine it until it hugs the shape of the rail curves to an acceptable degree. If you want to match polyline rails, it would probably be expected that you would use only those existing segments for your rail curves instead of refitting completely new ones. That introduces a kind of different complication to the whole thing.

In general one of the parts that you will have to solve at first is how to synchronize the point structures of the curves involved.

Sorry I won't able to really help you with this, I just don't have the time available for that type of a thing.

- Michael

I was really impressed by the Catia demo. I think it follows the standard sculpting workflow of most SubD apps, but includes better tools for manipulating hi-res hard surface objects. Most SubD sculpting apps coming out now focus primarily on brush tools. I would like to see if Catia can handle complex boolean operations like PowerNURBS's Detailer can. On their Phone modeling tutorial they literally boolean text into surfaces, which is something I would never try with SubDs.

But like I said, Catia seems to be based on a sculpting worklow and I think MoI is attempting to create a drawing based modeling workflow; much like SketchUp has done.

I don't see the word "Nurbs" in the Catia-Inshape Poduct overview?
just"subdivision surfaces"
Are they integrated?
http://www.3ds.com/products-solutions/plm-solutions/catia/all-products/domain/Shape_Design_Styling/product/IMA/

and that cost something like 20 000 $ (?) :)

I looked into it a little just now and it seems the SubD aspect is a seperate modeling toolset from the NURBS modeling tools. I didn't see anything showing how they integrate to form a hybrid SubD/NURBS Modeling toolset beyond what most DCC apps provide, which are seperate Poly/SubD/Spline/NURBS toolsets. I saw great tools for modeling hard surfaces using the SubD modeler, but not much on how it handles booleans and trimming, the stuff that makes NURBS stand out to me. The closest thing I have been able to find to a hybrid SubD/NURBS tool is Maya, only because it can convert back and forth between the different surfaces well.

> I don't see the word "Nurbs" in the Catia-Inshape Poduct overview?
> just"subdivision surfaces"
> Are they integrated?

Well, it is a bit subtle but one part mentions: "Moreover, this technology enables the creation of surfaces compliant with any CATIA V5 applications."

That means NURBS because the other Catia applications are NURBS based.

- Michael

> But like I said, Catia seems to be based on a sculpting worklow and
> I think MoI is attempting to create a drawing based modeling workflow;
> much like SketchUp has done.

Hi Joe, yes this is exactly correct.

And there is still a lot more stuff that I would like to accomplish within the "drawing-type" workflow first before really attempting to do more "sculpting-type" stuff.

I'm not sure how well it will work to try and merge both types into a single app. It is something that I am interested in experimenting with maybe a few years down the road.

- Michael

Well that will be a great day for modelers I'm sure! I know that the drawing-style workflow is only now starting to "click" for me, and now that I have seen the light I'm really excited about working with MoI. I was surprised at how quickly I was able to put together the sword concept I posted tonight. Sketchers and vector artists are going to love this app if they give it a chance.

That's ok, you gave me exactly what i needed :)

I will be using max's bezier curves. There are already a number of scripts for reconstructing a spline with a chosen number of points, so "syncing" the used splines shouldn't be the problem... more the interpolation of vertex positions inbetween... not exactly sure how this is done math-wise though. That's why I needed some references.
I think I'm gonna code some modules. one for syncing up the splines outputting a number of values for the position of each start/end-point, one for making a poly plane and making it editable on a sub-object level, and one for placing the outer vertices on the positions found in the first module, and then interpolating the rest into position. Two of those are a breeze (theoretically) the last one though... :S
Closed spline sweeping will come later :P

HAH! Who should have known! It's already there! :D

Seams like max's ever so shitty NURBS already has the convertion methods (b-spline > swept NURBS > Poly surface) all I have to do is script it all for automation :P The results are perfect, and it can do different kinds of optimizations too (not really a good choice I'd say, since it would ruin the edgeflows)...

So I guess I just saved myself alot of work :)

If there's one thing I'd like to see in MOI in the future is T-Splines if possible...

Michael, are T-Splines something that can be wired into MOI in a future upgrade? Or are the methods incompatible with your libraries, etc?

-Will

Hi Will, I haven't talked to the T-Splines guys about anything like this.

It would be a while before this would be possible - the T-Splines guys need a pretty comprehensive plug-in mechanism to make their stuff work. I don't expect to have proper documented support for doing plug-ins into MoI for a while yet.

The methods they use are compatible with MoI's NURBS surfaces, as far as translation between a t-spline object and a NURBS object goes. But there is a lot more involved than just translation - they essentially would need to add a new type of object to MoI to handle the editing of ther T-splines surfaces.

- Michael

Thanks Michael, I wasn't expecting anything immediate, just hoping perhaps that one day in the future, T-Splines might make it in as a nice feature addition to MOI.

-Will