OBJ export questions

Support Modeling
1

RhinoObjImportSharp
RhinoObjImportSharp1419×1426 138 KB
A
A1593×1494 189 KB
B
B1697×1515 125 KB
C
C1700×1479 769 KB
II’ve been intensely learning and using Blender for about 4 months. My focus is on helmet design. In some areas I have gotten super advanced, while my knowledge is certainly lacking in other, more basic ways. I’m embarrassed to ask some of these questions.

I want to model as low poly as possible and export an .obj that can be used to generate final tooling databases using Pro-E. Having a low poly model is important because the client is always changing their minds and it’s good to be able to adapt easily. Rendering is moderately important, but it’s not as important as having a quality .obj in the end.

Regarding the subdivision surface modifier:
There’s Render, Viewport and Quality. The online manual says to not have Render any lower than Viewport. And Quality “How precisely the vertices are positioned (relatively to their theoretical position of an infinitely subdivided mesh”. Huh?

What I’ve found is if I set Viewport on a mesh to 3 and export an obj to Rhino3D, edge creases set to 1 come through soft. Whereas if I set to 5, the same edges come through razor sharp. I don’t notice any difference on export of Render or Quality. Am I missing something important on export if I don’t have Render at 5, Viewport 5 and Quality 5? Are there some standard settings I should be using like all set to Level 3, or 4?

And maybe even more fundamental, I don’t know if I should be using edge crease, mark sharp, edge loops or bevel modifiers for my vent edges. I like edge crease because it’s quick and keeps poly count down. But when I use edge crease, I’ll select an edge, Shift+E and add a crease at 1.0, then reselect the edge Shift+E again and it says 0.00, or -.245? Why does the edge crease value change all the time? Also when changing to a number like 0, it doesn’t seem to affect the radius at all? I frankly don’t see any difference if I have it set to .5 or 1. Maybe that’s the reason to use a bevel modifier? I’m lost.

Does it make any difference on .obj export if I use Shade Smooth, or Normals> auto smooth?

I’m attaching images showing .objs as they import into Rhino and screenshots of a typical vent that I’ve been using edge creasing on. Is there a better way for me to be doing this?

Sorry for the long winded question. I really don’t know who to ask for help.

RhinoObjImportDull
RhinoObjImportDull1536×1532 134 KB

2

Are you trying to produce a mesh that will use a subd interpolation method in Rhino or ProE?

As far as I know, there is no standard for edge weighting/creasing that will transfer to your CAD application so its likely you will need to redo the weighting/creasing in your CAD application.
Weighted edges in Rhino are not currently implemented so you could not generate them within Rhino, although I believe a hard edge without any weight is possible.

I think the best approach would be to ask this question on a Rhino or Pro-E forum to get better info.
You probably won’t get a lot of people here with specific CAD app experience.

3

I’m not trying to produce a mesh that uses subd interpolation. Simply an export .obj that reflects what I’m looking at on the screen when I’m using Blender. I’ve actually done this on 5 separate helmet projects successfully but trying to understand Blender’s subdivision surface modifier better. Render at 3 or 4 works well. Viewport at 4 or 5 seems fine. Quality? I don’t know. The online manual says “Using higher values does not necessarily mean real improvement in quality, ideal results might be reached well before the maximum Quality value.” That’s really confusing. I can’t see any difference in the surface quality when I output at 1, 2, 3, 4 or 5. What setting will result in the smoothest surface? 1? 5?

And what about my vent geometry? How could it be improved? Would I be best using edge loops, edge creases, bevel modifier…?