Fix weird loop in 3dm file

openNURBS
#1

Hi all, I have a 3dm file (representing a cutted spring) obtained by a couple of conversion (solid works>step, step>3dm). In this file , the outer trim loop of one of the face (the spiral) is somehow “weird”, in this sense: 2d parametric trim curve form a close loop but this have a form like a “C” (maybe it’s not easy to understand, I can upload my file if needed).
As I’m working on a custom nurbs tessellator, this “weird” shape is very hard to detect and also to manage, but if I open this file with an editor (Moi3d) it opens correctly. So my question is: is that a case of malformed trim loop (in this case there should be a way to managed it) or am I missing some informations of trim curves?

#2

Here’s the file
error.3dm (145.5 KB)

#3

Hi @miquik,

If you use Rhino’s Check command on the Brep, you’ll see this:

ON_Brep.m_T[4] 2d curve is not inside surface domain.

Was this file created by reading a STEP file into Rhino?

Thanks,

– Dale

#4

Thanks for the answer Dale,
I created this file importing a STEP into MoI 3D editor.
Maybe some trim is not inside surface domain but this is not the main problem. If I call Opennurbs IsValid method I obtain: Seam trim ON_Brep.m_T[6].m_iso = E_iso but matching seam ON_Brep.m_T[9].m_iso != W_iso; indeed I have 2 trim (on a face) both E_iso (to be correct they are coincident).
If you plot outer trimming loop of the face with index = 2, you will see a self-touching polygon.

So now I know I can check and intercept these “weird” cases, but how to handle this? I think Rhino can easily open and visualize that file, but how? Does it rebuild a new corrected trimming loop?

Thanks

#5

Hi @miquik,

I’m confused. Does the STEP file import onto Rhino correctly? Can you upload the STEP file?

Thanks,

– Dale

#6

I don’t have Rhino I don’t know if the file will be imported correctly. I have MoI 3D and this can open correctly (well there are same small artifacts) the file.
I have the STEP file in my computer at work, I will upload it in next days.

Thanks

#7

Hi @dale,
I didn’t found original STEP file in my archive. I re-create STEP (and then 3dm) from original SolidWorks model and now trimming loops are all correct.
Maybe there was some error in conversion.

#8

Thanks for the update.

– Dale