How do you use import subd option in MoI.

Firstly I`ve thought that technology is implemented to import some meshes, convert them to nurbs and do some booleans and fillets on it. Booleans works for me but fillets almost always doesn`t.
Michael told be on different thread that fillets are complicated with calculate and it works only on clean curves and surfaces.

1) Is there some trick to clean a messy curves and surfaces generated after obj>subd conversion to nurbs?

2) How do you use your subd meshes after import? Do you use it only as bakcground reference to build new cleaner curves and surfaces inside MoI? I have strange feeling that I use it in wrong way and I have to optimistic vision of that conversion :)

I hope that some day it will be so easy like: take some subd meshes, convert to subd and then to nurbs and after it you may use all commands without worry about topology becouse you chave clean solid :) I know it`s sci-fi wish :)

I`ve tried also fillets in Rhino 6 and surfaces also exploded in similar way (quite low subd mesh with additional loops on hard edges). I`ve heard that Rhino 7 will have more commands to support SubD modelng. I`m curious if subd meshes created in Rhino 7 will also explode after boolean substraction and adding fillets over it same way as imported ones. If yes then whole point of merge subd modeling and nurbs is not so seamless as I thought before.

I love subd creation of surfaces but I hate blending them and I hate to make fillets on complicated shapes. I love nurbs precision, blends, nurbs booleans and fillets and I don`t like creating organic shapes in them. I wish that both worlds will be mixed seamlessly someday.

Cheers!!!

Hi mdesign,

> 1) Is there some trick to clean a messy curves and surfaces generated
> after obj>subd conversion to nurbs?

Sorry no, there's no trick for this. It's better to have a fairly sparse and already clean sub-d surface for this workflow.

Can you post some examples where you're running into problems?

- Michael

This was created after 3 meshes import as subd (it`s sum of one boolean addition and one boolean substraction in MoI after import).

I`ve tried to do also ShrinkTrimmedSrf command on it becouse those surfaces are much bigger than real surfaces are. This file is too heavy for such a small thing.

Even after trim it`s too dense for fillet I think.

Is there some way to convert it with some less resolution? With lower subd level to have less points?

I create complicated shapes in subd but my cages are low poly.

Hi mdesign, can you please post your original .obj file too?

> Is there some way to convert it with some less resolution? With lower subd level to have less points?

You need to create a lower resolution control age to get a lower density conversion. There isn't any way built into the converter to reduce control cage complexity, it's assumed that you will have already done that in your poly modeling program.

> I create complicated shapes in subd but my cages are low poly.

Maybe you have an very very different definition of "low poly" than I do? If you have like a hundred polygons across your object that is not what I'd call low poly at all.

For filleting you would need to avoid these kinds of very tight bends in your object:



There isn't any way that a fillet is going to be able to cross over that tight of a bend without the fillet getting all bunched up on itself.

- Michael

Hi mdesign, so I just thought right now that maybe the problem is that you're exporting out an .obj file that's been subdivided by a few levels already?

If so then that's the problem - you need to export out just the level 0 control page, no actual subdivision applied to it yet.

- Michael

I`ve attached one of objects from Modo.

I can`t share whole set of objects without rebuilding it becouse of NDA.

That attached mesh is a good example. I model with subd many hard surface models during my regular daily work. To do hard edges in subd I have to give additional loops near hard edges which cause such a tight bendings (to force hard edges there). Doing whole subd model without additional loops for hardening edges is very rare. I can`t remember even one of my subd meshes which had only smooth surface without additional loops near hard edges so it`s a big limitation.

This is example: I`ve doubled same mesh which I`ve attached. One cube has got subd turned on and the second has got subd turned off.



Giving those additional loops is a way to create demanded shape in subd.


Other thing is subd levels. | may change subd levels in Modo but I can`t export it with obj :) So in my opinion those obj are exported as low poly cage without info about subd smoothing. I`ve looked that kind of info in notepad but those obj don`t have any info about subd levels so I can`t change it to lower level without doing it in MoI (becouse it`s imported on lowest level without any smooting info).

Thanks Michael for helping me out with deeper understanding of that workflow.

Hi mdesign, so you can put fillets on a model like ok just as long as they don't have to cross over the tight bend, like this for example:



If they have to cross over a tight bend the fillet radius has to be smaller than the radius of the bend. A larger radius fillet going trying to go across a tight bend will be bunched up like this:



That's not really something specific to sub-d conversion, if you constructed tightly bent things in MoI directly it would be the same thing. In CAD usually the smallest radius fillets go on at the end.


> Giving those additional loops is a way to create demanded shape in subd.

That type of shape will convert over ok but it's highly unlikely that you will be able to fillet anything that runs into those areas, unless the fillet radius is very small.

Really the main idea for a hybrid workflow is not that you would be making the hard surface model in sub-d, it's intended that you would do the hard surface model in MoI and use sub-d for doing more organic smooth blob stuff to use as a base shape. Think of stuff like a car body, base head shape, chest plate, boat hull, not really stuff with small scaled details.

- Michael

Your last sentence was crucial for me. Thanks a lot. Now it`s clear to me.