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I've been looking at many different engineering apps for a personal project I started some time ago which needs a large amount of precise modeling, fillets, ...

I've looked at the websites of :

- SolidThinking (demo tested)
- SolidWorks
- Moi 3D
- Groboto (demo tested)
- SpaceClaim
- Ashlar Cobalt
- Rhino

It's amazing how many other tools coexist to those.. and they all are called 'best / easiest'.
*cough*

But again, It seems I'm not only limited by the budget and time, but especially by the fact that there seems to be no solution in those tools what so ever which covers the proper translation from nurbs to polys, that generates truly closed meshes without those damn visible seams between surfaces and fillets.

How do you guys handle this issue professionally to port the geo to maxwell ?

well almost all meshers detect surface edges and therefore tessellate along the filet lines.
EDIT: good ones will make sure the polygons meet perfectly along the edge. maya (v7 was the last i used) was always horrible in that regard. the filets were tesselleted differently than the meeting surfaces, so you had gaps unless you tessellate the shit out of the model.
i have yet to see a mesher that looks at a nurbs or solid model as a volume and meshes it independently of the surface patch edges.
sort of like the automatic retopology in 3dcoat and others.

also: most filets are just tangent filets, so when rendered in a glossy material you will always see the continuity break. so unless the filets are G2 you will always see the break in the converted polygon mesh as well.

well, then I could merge the polys at least and smooth the normals locally.


what's an example of the 'good ones' ?

what apps are you guys using to address this issue ?

I've used maya too in my nurbs modeling course at the gnomon school of VFX back and have been fighting especially with the advanced tesselation for mental ray. resulting : headache !

[ I wish Maxwell supported true NURBS rendering .. ]

While many Meshers for Nurbs certainly can be improved greatly you are probably looking at the wrong end.

While SubD-Bevels sufficient Subdivision and All Quad-ness given always blend perceptively Smooth this is not so with Nurbs.
By Design!
If you have only fillets with Tangency Continuity you can increase the Render-Mesh-Density ad infinidum and
you'll still see a seam. What you need for smooth transitions is a Model which has Surface-Blends of at least G2 Continuity.

I am not sure if I get your point.

G2 continuity makes sense, of course, but what if you have :

1 edge between 2 surfaces (slight curvature) with G2 continuity, BUT
the edge is tesselated (to renderable polys of course) on one surface with e.g. 16 quads and the other surface has 15 quads on the same edge.

--> nevertheless you have G2 continuity on the NURBS geo, you still have the very small gaps there when converted to polys. yes, infinitesimal tesselation would solve the issue, but that's exactly the point ..

back in the day when i still used maya i exported the nurbs to rhino joined them to a closed surface (ctrl J) and meshed them there. rhino then makes sure the polygons along two neighboring surfaces match perfectly and are joined.

the solidworks mesher also works that way - no gaps. you control the desnity of polys for maxwell with the display quality slider.

moi 3d has a nice option to convert to quads only - but depending on the geometry you might end up with quads that don't line up at meeting surfaces

deadalvs wrote:I am not sure if I get your point.

G2 continuity makes sense, of course, but what if you have :

1 edge between 2 surfaces (slight curvature) with G2 continuity, BUT
the edge is tesselated (to renderable polys of course) on one surface with e.g. 16 quads and the other surface has 15 quads on the same edge.

--> nevertheless you have G2 continuity on the NURBS geo, you still have the very small gaps there when converted to polys. yes, infinitesimal tesselation would solve the issue, but that's exactly the point ..

Yeah, seems to be a Maya issue. Rhino stitches these patches together using Triangles.
MoI actually should give you better results.

yolk wrote: moi 3d has a nice option to convert to quads only - but depending on the geometry you might end up with quads that don't line up at meeting surfaces

Actually that's Ngons which look like Quads. That's why I call MoI a PseudoQuad-Mesher.

you're right - now i remember having difficulties importing these meshes from moi into programs that did not like ngons. my bad

okay .. thanks for the inputs so far.

can I ask one of you guys to post an example with a sphere which is intersected by a round cone and a blend shape / fillet between ? both as igs (or similar nurbs format) and obj with that rhino mesher function (very good quality would be nice ..) ?

that'd be amazing for me to test the thing ...

I've been wondering this for a while but didn't realize a solution existed! Make sure to let us know which solution you end up finding to work for you.

i sent you this

the filet is curvature continuous.

thanks for the files .. !

here some rendered results, still not yet happy though. you can see those seams still quite clearly.

I think the issue is that even though there's a lot of polys added in the blend shape, there are just about 8 rows of polys and the rest of the tesselation is planar on those 10 rows, not again following the curvature. Additional smoothing of the vertex normals fails like this obviously.

Are there any settings for this in Rhino ? I guess you can go higher with the polycount .. ?
Can spheres be converted to polygons 'tetrahedrically' or always following the param lines ?

I bought Moi3d for converting IGES files from SW. It works ok, it's not perfect, but it's capable of creating very dense meshes, which is critical to getting good smoothing. There are occasional flipped faces, but overall, it works well.

in Rhino, you can adjust mesh in tools>options>document properties>mesh.
by default it is set to jagged, you can switch custom settings on.
you will have to experiment a bit with different parameters, depending on size and complexity of your model.
i tend to use only the maximum angle setting (set to low value like 5) and the rest set to 0 (which means inactive).
or a reasonable edge length setting... can also be a way to get more meshy.