Full Version: Curves Modo<->MoI

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M: "...If so it's not making curves out of them right?"

yes, that second image shows obj after reimporting obj to Modo (it can`t see it as curve) but there is converter inside Modo to convert polygon edges or polylines to Modo Curves.

Thanks for your effort with trying to solve this export/import problem.

Polylines (2- vertex polygons) are exported as n-gons with vertices.

So it`s suppose that my way to import those curves is good but not accurate (different curve shape) as you said before.

Thanks for your time once again.

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Hi bartosh44,

why don't you use MoI to create the closed curves?

If you import you quad model into MoI v4 beta with subd2nurbs
you only need then to project some lines to your model ... ;-)



Regards
Stefan

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Hi Bartosh, so just to clarify, those example files you posted previously were those saved from a Modo Catmull-Rom spline curve or were they exports of 2-vertex polylines?

What happens if you try to export a single line with just 2 vertices in it to .obj ?

Maybe it's possible to make a script that parses these particular .obj files in a different way than the regular .obj converter but I'm not sure how it could identify an open curve like in your first screenshot versus a closed loop. An n-gon in an .obj file is implicitly a closed thing, there isn't any way for it to be labeled that it's supposed to be treated as an open curve instead of a closed polygon. And then the results of making a NURBS control point curve through those points is going to look different than the Modo Catmull-Rom spline curve.

- Michael

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1) Those files was export of Curves (not 2-vertex polylines) but with polylines OBJ looks same.
2) Single line without polygon is a polyline. Polyline with two vertices is exported as pure vertices without edges.
3) I`ve thought about vertex ID but if you will edit a curve then a vertex order will be broken so it`s not a solution

I wanted to do in that way becouse I do retopo on the surface of big 3d scan data. I`ve thought that I could do curve retopo in Modo and next build patches in MoI.

Thanks Michael for that Subd feature. It`s fantastic and it`s super feature. Only for that one feature it`s worth to buy your wonderfull software.

As I wrote before I solved my way to import curves from Modo to MoI as polygon strips. Maybe it`s not 100% accurate but I think it`s good enough.

I would like to ask about second way (MoI->Modo). Why obj export can`t export MoI curve without surface as f.e. polyline? Of course I can do same trick in other way. Build surface only to cheat exporter and remove it in Modo to have polylines which can be coverted to curves.

Edit: I`m not super specific becouse I have my Modo based workflow and with that thread I`m trying to do research of potential possible changes in my current workflow.

Cheers!!!!

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Thanks for youe example. It was only example with those lines. I need Modo for retopo over 3d scans (5-10million polys). I`ve thought to import main features lines as curves to MoI but I can do this as subd polygon strips.

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Hi Bartosh,

re:
> I would like to ask about second way (MoI->Modo). Why obj export can`t export MoI curve without surface
> as f.e. polyline?

Well, because it would be weird to do that, it's not supported by any programs to interpret an n-gon in an .obj file as if it was a curve.


> Of course I can do same trick in other way. Build surface only to cheat exporter and remove
> it in Modo to have polylines which can be coverted to curves

But this conversion doesn't work properly if I understand correctly. You're making a Catmull-Rom curve in Modo, the shape of the curve will be different than what it originally looked like in MoI.

Just taking the control points of a NURBS curve in MoI and then using those as the control points of a Catmull-Rom spline in Modo is not going to make the same curve shape.

Since Modo does not have a NURBS curve type in it, I don't really see how it's going to work to transfer a curve over to it without potentially weird mutations in shapes.

- Michael

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Thanks, Michael for your effort to explain this differences with curve shape. I think I understood it.

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