How do I make the T-spline surfaces uniform in Fusion?

[Anonymous]

Hello,

I have successfully converted some medical models to T-splines using Autodesk remake and inventor. But please, how can I make these T-splines uniform? The T-splines generated are of various sizes and they have remained on the body even after converting to a water tight model for analysis in ABAQUS.

I will like to make the T-splines of uniform size and have more control over each region they occupy. Please how can I do this?

Thanks,

Gaby

[PhilProcarioJr]

@Anonymous

It's hard to help without seeing your files and what exactly you are trying to do. A screencast goes a long ways to help us understand your problem.

[Anonymous]

Here is a screenshot

[PhilProcarioJr]

@Anonymous

Is this what your after?

[cekuhnen]

@Anonymous

That is also normal. TS decides on its own how the surface will be broken up into BREPS.

Phill showed you how you can manually refine that however with such a complex model you

have you will remain having a crazy BREP patch layout. Why is that an issue for you?

[Anonymous]

@Anonymous

Like Both @PhilProcarioJr and @cekuhnen mentioned, T-splines decides how to patch such geometry.

The only other way i can think of is doing the patching manually in T-splines. See here as an example: https://www.youtube.com/watch?v=SdMxlNhKBmg

Or by using another reverse engineering package and also do it manually.

@cekuhnen I'm assuming he needs lesser or uniform faces to help with his FEA. 

[Anonymous]

Thank you very much for the comments.

I will explore the different suggestions

[PhilProcarioJr]

@Anonymous

I am truly hoping no one ever uses the method in that video....

[Anonymous]

@PhilProcarioJr hahah

I hear ya, I just hoped it would clarify the point of manually patching.

@Anonymous

There's an old video about T-splines in Fusion where it basically shows creating faces/patches onto a geometry directly, however I can't find it.

I'll do a screencast when i'm at my desk.

[PhilProcarioJr]

@Anonymous

"There's an old video about T-splines in Fusion where it basically shows creating faces/patches onto a geometry directly,"

I would avoid this method also as currently in Fusion there is no way to deal with surface tension and the results are not accurate at all.

If you don't care about accuracy then this method is ok, but I would still avoid it....

The best way to deal with this problem is using a retopology app like Topogun on the scan mesh... then using the relax brush... then bringing that quad mesh into Fusion as a T-Spline and doing a conversion with keep selected edges. You can maintain accuracy and control over the uniformity of the model face flow and edges...

[Anonymous]

@PhilProcarioJr I was under the impression that "make uniform" command resolves surface tension, no?

And just for clarity, by surface tension you mean the "invisible" edge weights? as in opposite sides equaling 1 as in attached pic?

[PhilProcarioJr]

@Anonymous

"I was under the impression that "make uniform" command resolves surface tension, no?"

No, at best it will smooth out some kinks in the surface, but honestly it's junk...

Surface tension is the amount of edgeloops and their placement required to maintain the shape accurately, if you don't have enough the surface approximation will not match the scan model to many and you get kinks in the surface. I will try to put together more info when I have time. Surface Tension is next to impossible to handle manually thus the reason I mentioned the relax brush in Topogun as it calculates this for you and adjusts the edgeloops in the mesh for you.

I have yet to see a good video tutorial on T-Splines for use accurately as a CAD model. It can definitely be done but not the way the videos are showing.

[Anonymous]

Thanks @PhilProcarioJr learned something new today.

However, I think @Anonymous is more concerned with his/her FEA analysis more than perfect topology so reduction in faces is I think the real issue here.

[Anonymous]

Exactly...im concerned about the FEA analysis

[PhilProcarioJr]

@Anonymous @Anonymous

"Exactly...im concerned about the FEA analysis"

This is exactly my point...the less accurate the model is to the real thing the less accurate your FEA analysis data will be.....

In the end you want a model that represents as accurate of a model as possible while still allowing the simulation software to be able to mesh it.

[Anonymous]

Not to beat a dead horse 

@PhilProcarioJr depends on the analysis really. And on top of that, surface tension or imperfect (not so matching) topography wouldn't matter.

Normal practice in FEA is to "simplify" the model by removing fillets, holes etc etc. So a fem 1/10th of millimeters in non-perfect topology shouldn't matter much.

[PhilProcarioJr]

@Anonymous

When I run sims on models I don't simplify them and the simulation software doesn't (at least for me) so you guys must do things differently then I do which is fine. Carry on. 

[TrippyLighting]

What uniform does is it basically re-aligns the T-Spline handles. It does not always work, so a standard way to handle such situations is to actually export the control mesh from Fusion 360 and then re-import it as in that case Fusion 360 has to re-calculate the T-Spline handles from scratch.

[Anonymous]

Thank you very much. But what format do I use to export it to retain this new surfaces? I think fusion can only import stl and obj files. Or am I wrong?

[TrippyLighting]

.obj export is in form of quad meshes.

You need to make sure that you have disabled "Triangulate meshes" in the MESH preferences, otherwise Fusion 360 triangulates meshes on import.