NGON import bug resulting into OBJ to TS to BREP problems

[cekuhnen]

There is a bug with the OBJ NGON import

Here are the source files:

https://drive.google.com/file/d/0Byzv_NlyKp_2elhJZ1ota24xX0U/edit?usp=sharing

[jinhai.zhu]

Hi Cekuhnen,

Thank you for reporting this issue to us. Fusion 360 has some problems when dealing with this type of NGON surfaces. We logged it in our track system, and dev team will look at it later.

The third image, which shows empty after finishing form in timeline. The root reason is that Fusion 360 failed to convert tspline bodies to brep model. So there is no shape showed in the scene. The icon of this item also has a yellow background at that time.

Thanks,

Gavin

[deyop]

Claas,

What were your intending to do with the import?  Were you going to convert to T-Spline or BRep?  I am looking at the file now and see there might be a problem in how three colinear points on the top NGON are matching to the sides.  We will certainly get to the bottom of the problem.  However when I workaround the issue by creating faces between the top and bottom I get a T-Spline result that at first doesn't seem intented which made me ask the question.

Currently we consider the NGONs as a method for creating a T-Spline from a poly modeler.  Is there another workflow you are trying to support?  It will make a difference for how we set up conversions in the future.

Thanks

[cekuhnen]

Hi Paul,

NGONs area fantastic tool for simplifying meshes and specifically also with true SDS modelers to create great and fluid mesh quad surfaces.

For texturing NGONS where always a great tool in architexture work but with the recent addition in Blender with the sub-d engine it produces fantastic

mesh results which pretty much are similar to TS results. As you can see NGONS are also a great tool caping a surface like with the cylinder.

And while I use Blender basically it is the same with all other poly sub-d modelers such as Modo etc.

In this area TS needs to mature more. It also has dramatic issues with edge creasing even on very simple meshes which well again use NGONS.

The top mesh has all planar edges (no verticals) creased and TS bugs out again creasing everything.

This makes the use of NGONS and creasing a no go because I as a designer do not want to ask myself while modeling if TS can do it.

I just want to know that it can do it. Otherwise I can see designers simply ignoring it or those tools.

And NGONS and edge creasing are so powerful surfacing tools it would be a shame if they are not fully working as expected.

[deyop]

We discovered the OBJ file that was attempting to convert to T-Spline did not have connectivity between some of the faces.  This led to the conversion issue.  

Regarding your other points.  There are differences between the T-Spline capabilities and poly/SubD modeling that I don't expect we will be able to resolve easily.  The main difference being the underlying math representation of the T-Spline that ensures precise conversion to NURBS models also imposes limitations on the modeling methods.  It can certainly be improved and your comments are appreciated and taken seriously.  Thanks for continuing to provide us with feedback.

When you create the mesh results from the poly model  in Blender how are those tessellated meshes converted to NURBS surfaces?  Are there tolerance issues? 

Thanks

[cekuhnen]

Hi Paul,

The obj mesh in deed has the planar faces separated to prevent the edge crease problem TS has.

I would have assumes that the NGON would not be an issue for TS to turn into
a smooth surface matching the curvature of the vertical surface.

The main reason why I added the caps is because I was testing a solid modeling workflow in Fusion to cut those dogbones out of wood planks all at once because in this regards the split command cannot deal with many inputs at once and Fusion also has no cap tool capability like Rhino does for doing this at all curves selected not just one object.

All RAW Files in Rhino:

I select everything once run the make solid tool:

And this will be the result:

As you can see this was a select all select command and done task.

I know that at one point Fusion should have a similar boundary fill and ability to also perform split command with many objects to split

at once.

But currently Rhino is faster.