Here's a other try using maya, still thinking it might be a cool way of working ... however there as some areas that are quite
complex (red lines) and need probably to be rebuild/simplify too.

Maybe a little polymodeler in Moi ? :D

Hi all,

Testing some neat stuff there guys.

- Pilou -> Nah Moi is a nurbs and for myself i would love that he stay like that (Michael decide anyway). I have enough modeller with Carrara, Hexagon, Cinema 4D that i added Moi because of the NURBS.

Hi Kevin,

You wrote:
> I know this functionality does not exist in MoI and last time
> I used Rhino it doesn't exist either.
> Once a surface is created, say a swept surface and then trimmed.

MoI does not currently have anything to insert new points into an already existing surface directly, but Rhino has had that function (InsertKnotSrf command) since the Rhino v1.0 release. So that is probably something that you just did not know was in Rhino. That is understandable since there are so many functions in Rhino it can be difficult to learn them all.

I do expect to put this into MoI as well, just the surface control point manipulation toolset has not been a major focus for the earlier versions of MoI since I generally expect that someone who is very interested in pulling surface points around would want to use a subd modeler for that type of thing instead since those programs are totally dedicated to that kind of workflow and are handling that type of thing very well already.


> Or could something like 3DS Max's FFD modifiers be
> programmed into the software.

Yeah, I think that this will be able to happen eventually. But it is not an easy task to make this happen on solids that have joined edges at trimmed surface edges, instead of the natural surface edge of the underlying surface. The latest Rhino version 4.0 has added some various functions to do this kind of thing, so if you want to deform NURBS models with cage editing, you could look into using Rhino for doing that.


Please understand that I only have so many hours in the day to work on MoI. It is just not possible for every single conceivable feature across every single conceivable style of modeling to be added into MoI all at the same time. Many things will take some time to add.


> My agenda with this thread is as follows
> <....>
> 3. To show Michael some of the problems users face when
> modelling up difficult subjects which may help him (it may not)
> further develop the software.

Definitely not a bad plan, and I appreciate the effort!

However, just to be clear, I am already completely aware that MoI's current toolset is not as good for making "point squishing" type editing directly on surface/solid models as you would do in a subd modeler.

It has actually been an intentional design decision to focus priorities in MoI on areas that are not exactly the same as other programs. That can help people get a more well rounded toolset so that they can get more of an expanded toolset when using MoI along side of another program, rather than trying to do a kind of half-effort on duplicating things that are already handled well in your other software.

Over time I do expect to fill in more of the kind of toolset that you are asking about with point squishing, but since it is working well for you in your other modeler, that is all pretty much going as intended currently for the early versions of MoI.

It is the general intention that you would use your other software to do the tasks that suit it better, instead of trying to do those in MoI.

- Michael

Hi PaQ,

Yeah that ability of Maya to transform subd to NURBS does not seem to be very frequently mentioned or used for some reason. But it could definitely be a useful transfer method.


> Here's a other try using maya, still thinking it might be a cool way of
> working ... however there as some areas that are quite
> complex (red lines) and need probably to be rebuild/simplify too.

That kind of smaller patch refinement will generally happen in areas where you have a vertex with a valence of other than 4, meaning more than 4 edges radiating out from it.

Like in this case you seem to have a kind of edge loop that terminates here:



So that created a vertex there that has a valence of 3, and the one right above it has a valence of 5 with 5 edges coming out of it - if you can avoid those where possible then it will probably eliminate that kind of patch refinement.

Like in your case here if you continue that edge loop to the end instead of terminating it, that will probably get fixed up.


There is a common relationship between some of the mechanics of how NURBS surfaces work and how subd surfaces work.

The way that Catmull-Clark subd works, it is actually completely equivalent to a NURBS surface in areas of the subd that have quad polygons with all vertices of valence 4.

Those areas of the subd surface have an exact and natural translation to a NURBS surface.

Areas where that is not the case like at your valence 5 spot, do not have a natural equivalence to NURBS so those areas get processed with a kind of fitting or refinement type scheme to get some NURBS surfaces in there that are close enough to the subd surface. But the refinement will generate additional surfaces, that is what you are seeing there.

- Michael

Hi PaQ,

I see you had another vertex of valence 5 up near the front bottom of the canopy there too, I'm kind of surprised that there was not some additional refinement in that area.

I would be a bit suspect of the surface smoothness in that area, although it seems to look pretty good.

But maybe it just happened to be close enough not to need refinement.

- Michael

Hi Michael,

Maya can only convert what they called 'subdiv surface' into nurbs, so in the image posted, it's the middle model. This model is a conversion from
the polygonal one. The subdiv shape allready shows some complex area in the front of the model, and this seems to be translated into the nurbs model at the end.

I have just no experience about how subdiv actually work, it seems to be way more heavier than catmull scheme. Maybe I should first learn this part to have a better control of the nurbs conversion.

I didn't remember having this kind of result with the t-spline. With the t-spline plugin, the nurbs flow was more looking like the maya subdiv one. (I'm not sure if this sentence is clear enough :P).

Hi PaQ, I see - I'm not really familiar with some of these details on how Maya works, but it appears to me that the middle "subdiv surface" has already been divided down in those valence 5 areas.

So my guess is that a "subdiv surface" in Maya is some kind of hybrid object, which has already been prepared in its structure for converting to NURBS? Something like that anyway.

But if you continue that edge loop that I showed above to the end of the shape in the original polygon model before conversion to "subdiv surface", it will probably simplify that area that you were pointing at with the red arrow above.

You can't always avoid such areas, but in areas that you can it will probably make the result more simplified.

- Michael

Yes I'll give a try with a pure quad model, ... at the moment I'm still learning all the selection and objets organisations tools ... (in other words, I'm nowhere :o)).