Can't edit quad mesh generated from blender

[rbuckDF7GX]

I have a triangular mesh obj generated from a 3d scan. Wanting to eventually go to t-splines and prep in fusion, I have used Blender 2.8 to re-mesh into quads. This seems to import well into F360 as a mesh (insert mesh method), but the resulting mesh is not editable, i.e., with the mesh pallet turned on, only the entire mesh body can be selected, not individual faces (or selections of faces). The Quad Mesh does convert to t-splines where individual vertices/edges/faces can be edited in Form mode, but the model is large and requires cleanup before it can be successfully converted into a b-rep. These edits are painfully slow in Form and best performed if possible as a Mesh.

Any suggestions on how I might attempt this?

[jeff_strater · Accepted solution]

@rbuckDF7GX - you have correctly described the situation.  Fusion mesh cannot edit quad meshes.  The only thing you can do is to convert to TSplines, or to triangles.  If the TSpline operations are slow, it is probably because you have a very large mesh.  Can you reduce it in Blender, before bringing it into Fusion?  The only other option is to edit as a triangle mesh (don't convert to quads).  What made you want to convert it to quads in the first place?

[TrippyLighting]

How familiar are you with Blender and Fusion 360 ?

Where did you hear/read about that workflow ?

Do you understand the differences and similarities between meshes, T-Splines and NURBS ?

I have a pretty distinct feeling that I know the answers to these question, but don't let that deter you from being as detailed and as specific as you can when answering my questions.

[rbuckDF7GX]

Thanks for the reply, Jeff. It is a large mesh, and I know next to nothing about Blender. So while I'm sure I can reduce the mesh in some areas in Blender, I need to come up to speed on a new tool. The better question is the workflow. I am looking to take my mesh surface to a solid for integration with other models and ultimately CNC machining. The WF of quad to t-spline to b-rep looked like what I needed. The mesh I have complains about self-intersecting surfaces when trying to complete the t-spline conversion, but identifying problems to correct is slow and sporadic (errors don't always seem to be highlighted by the tools).

I'd like to get to a full solid since I'm sure further sculpting will be required to accommodate CAM.

It _is_ a large mesh (north of 20K faces I believe) - some areas of detail I don't want to lose. Back to triangles to remesh and then try to go to b-rep from there?

[rbuckDF7GX]

F360 - Not bad

Blender - not at all

WF - Auto desk and various youtubers, though with re-cap instead of blender for re-meshing to quads.

Meshes, t-splines and nurbs - don't ask me for the math on the differences between t-splines and nurbs.

Obviously I don't know any of these things as well as you do 🙂

The issue is the quad re-mesh from Blender?

[rbuckDF7GX]

Sorry... think I should have accepted that as a solution as well.

Thanks.

[TrippyLighting · Accepted solution]

The issue might indeed the remesh from Blender. What remeshing method did you use in Blender ?

Could you share the original triangulated mesh ?

I have not use the newer remasters available for Blender but have used InstantMeshes many times. Here's one of my own tutorials:

if you need to make edits to large, densely meshed T-Spline objects in Fusion 360 then you should definitely turn from smooth view mode to box-view mode. When editing the T-Spline there is a display modes button in the top menu bar that has three choices:

Depending on what edits you want to make you might want to enable soft deformation:

Otherwise you'll have a lot of work ahead of you. People experienced in Sub-D modeling try to avoid dense meshes at all cost for that reason. The golden rule is to start modeling with the least number of polygons to reflect the shape you want to model and only when you are satisfied with that basic shape should you add detail by locally refining areas and adding by adding additional polygons and edge loops.

The models generated my modeling result in meshes that have higher polygon coins in areas with higher level of detail and sSub-D models are in fact a very efficient means of representing very detailed models.

Scanned/Re-meshed models on the other hand have a fairly even polygon distribution because the re-meshing algorithms do not take local detail levels into account. So when there are areas with a lot of detail adjacent to areas with very little detail, if that level of detail needs to be captured result in the large areas being way too desalt mesh for any meaningful way of later modification. It depends, however, to a degree on what modifications you want to perform.

When re-meshing scanned object for further use in Fusion 360 the re-meshed mesh and T-Spline serve mostly as intermediary data carriers to get to  NURBS surfaces or in case of a solid model  NURSB surfaces contained in a BRep.

What modifications would you want to do to the objects ?

[rbuckDF7GX]

Peter, thanks for the excellent reply. I REALLY enjoyed your tutorial and FWIW am now a sub.

I have been using all of the methods you propose (Meshmixer, Blender, box mode, soft-mod, etc. - though far less proficiently I'm sure), excepting instant-mesh. When exporting fm Blender I re-meshed to quads. I'm going to give instant-mesh a spin.

Can't tell you how valuable it is to see someone else have success with a chosen workflow and know you're not trying to accomplish something a given tool can't support.

Thanks again!

[rbuckDF7GX]

Not to beat a dead horse, but for posterity, Instant-mesh worked great. The Blender conversion to quads was generating a fair amount of weird geometry and artifacts (at least the way I was using it). F360 repair body wasn't catching all of the geometry errors. 

[TrippyLighting · Accepted solution]

It’s not a dead horse at all.

The “standard” remesh modifier Blender isn’t that great. However, there are 2 plugins available at Blendermarket.com

Those promise to work better.