That isn’t a very good conclusion. Look again at the data.
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yeah Andy and Jussi are right. The problem is not the Mesher2, it does a fine job meshing a MOI-created polysurface. The problem (for both meshers) is when the input is a Rhino-created polysurface.
So…
This intention of this post is not to pin the problem on Rhino’s fillet command - the generated surface is just as valid as the Moi one. The problem is that it doesn’t lend itself to being meshed as neatly in this case - in the very simple case of a filleted box.
I’ve been hearing for many years about users who take their Rhino model and use Moi to create the mesh because apparently, the Moi mesher is better. This means that Rhino NURBS are meshing better in Moi than Rhino even with this difference in the direction field. I suspect that we have to actually compare real-world cases.
We also believe Mesh2 should get very close to the meshing quality offered in Moi - if not better.
So please - let’s see from user models run through the Mesh2 command - and let’s see if we’re getting anywhere!
- Andy
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But Jussi’s images would suggest that isn’t the case, even in this very simple example. What could be different about the MoI and Rhino NURBS cubes that would give rise to such different mesh outputs? The meshing results of the two look reasonably similar. There’s no point in progressing to diagnose more complex cases until this one is addressed?
Or have I missed something? 
And be careful not to get splinters off that non-AA’d cube in Rhino 
Can you share some details on the meshing algorithm and how it differs from the original Mesh command in Rhino? Thx!
No - I think you’ve missed something.
If you look at the results, the mesh produced by Mesh2 is basically identical to the Moi mesh in both cases.
The difference is that in the cube that was made in Rhino, the direction field of the filleted corner is not parallel to any of the cube sides - it’s basically at 45* to the cube, and the pole is not at one of the corners. This means it’s much more difficult for the mesher to produce a well behaved mesh.
Menno
It’s not all that much different from the Rhino one - it’s basically divides along the surface UV and then does adaptive subdivision followed by stitching.
However, it is optimised for the visualisation case, and it does a much better job of removing extreme aspect triangles and large differences in triangle area than the Rhino mesher.
- Andy
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Yes, Andy is right about the directions. Both Moi and Mesh2 seem to follow the surface uv directions when tessellating.
Hi @andy, i do not see this here yet. If i set my aspect ratio to 3 it still creates very long skinny triangles even when “Quadrangulate” is enabled.
@Jussi_Aaltonen, i’ve made a test with default settings and a 20x20x20 Box with filleted edges. It seems to create overlaping triangles in 32 locations. I can remove them by enabling smoothing but would like to find out if this is a bug which can be prevented. Below is the file and settings used.
Example.zip (164.1 KB)
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Clement
It will still create skinny triangles during the stitching phase. You might try the delauney option to get rid of them.
- Andy
Hi @andy, OK i’ll try. Please note the example above. Imho, it should never create overlapping polygons and if so it should report them as problem.
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Clement
Sure - Jussi will look into it tomorrow.
- Andy
Thanks @clement, looks like surface tessellation goes wrong and adds mesh faces that go over the polysurface face edge. We will look into that.
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hi @Jussi_Aaltonen, are you the person working on Mesh2? I just tried to make as STL of a detailed model here and god, oh god. You guys need to see this. Not good.
Yes, @gustojunk, please use http://www.rhino3d.com/upload and set recipient to jussi@mcneel.com.
done.
Thanks, I’ll take a look!
@gustojunk There’s already one bug track item with problems much like these. I’ve added your model there. Unfortunately I don’t know when I will have time to look into that.
I noticed a while back that OBJ export was terrible, it generated really messy meshes. Is this fixed now?
@pascal, do you now about the OBJ export?