How to smooth FBX-imported CAD data of a car?

[MANUEL_MOUSIOL]

Hi everybody,

I had this a few times now, but I never really resolved the problem and it is driving me mad.
Often when I get CAD-data that is exported (probably from Maya) to FBX the surface seems broken at random points. Polygons are not connected anymore, which makes it obviously impossible for 3dsMax to get a smooth surface.

Please see this closeup of the (most important) metal body surface of the car:

This is the unsmoothed state.
Here it is auto-smoothed:

and here I tried welding the vertices by selecting all of them and welding to 0,01mm


As you can see nothing really helps. Welding does a little bit but detailed modeling is lost and results in small shadows/highlights in the surface. It is also a lot of work to go to every single part of the car and weld, since I dont have just one object but hundreds that compose the car.

As I have no way to get other data than the FBX I am wondering what I can do to get this model back into a good shape.
Any suggestions?

Thank you for any help in advance!

[Moriah]

The normals come locked from maya, only solution i've found so far is to put an edit poly on top of the mesh, it unlocks them and makes them smooth again. I've had this issue both from Maya and C4D.

[MANUEL_MOUSIOL]

The normals come locked from maya, only solution i've found so far is to put an edit poly on top of the mesh, it unlocks them and makes them smooth again. I've had this issue both from Maya and C4D.

thats what I did when I welded the vertices (see last image), so not perfect yet.

[DaveKW]

We get data like this all the time but the normals are explicit so there's never any problems as the normals are taken from the CAD surface and not just averaged like welding and smoothing would do. Can you request another FBX that keeps the normal information?

[MANUEL_MOUSIOL]

We get data like this all the time but the normals are explicit so there's never any problems as the normals are taken from the CAD surface and not just averaged like welding and smoothing would do. Can you request another FBX that keeps the normal information?

unfortunately not, that is why I am asking here. Client got the data from his client and nobody has a clue and it seems no possibility to request anything.

[MANUEL_MOUSIOL]

I solved the problem!
At the FBX import I turned off "smoothing groups" and the surface looks beautiful.
sounds strange but thats the world of 3D files: it doesnt always make sense

thanks for the help though!

[DaveKW]

That makes sense as it wouldn't really have smoothing groups. Glad it's sorted

[kosso_olli]

I suggest not to use the standard weld tool from Edit Mesh or Edit Poly on CAD data. It breaks more things than it fixes. The ProOptimizer has a function to weld vertices, that works like a charm. Unrelated to the problem, but just an advice.
Also, never put an Edit Poly onto the imported data. It instantly breaks normals. (Pics 1 and 2) Right click>Convert to Edit Poly instead. Subtle difference, but it preserves normals correctly.
If the geometry comes from software like Catia and it hasn't been broken by the Maya POS, you can select large groups of polies using the element sub object. If the data was processed correctly, it should select the original surface patch from Catia or wherever it came from (Pic 3)
Based in that, you can hide the unnecessary edges like this: Edit mesh>select open edges>invert selection>set to invisible in surface properties of edit mesh. Result shown on Pic 4. Looks good, eh?

[Pixelcon]

I suggest not to use the standard weld tool from Edit Mesh or Edit Poly on CAD data. It breaks more things than it fixes. The ProOptimizer has a function to weld vertices, that works like a charm. Unrelated to the problem, but just an advice.
Also, never put an Edit Poly onto the imported data. It instantly breaks normals. Right click>Convert to Edit Poly instead. Subtle difference, but it preserves normals correctly.

Pro-tips there for any field of work... cheers!

[kosso_olli]

I just added some more together with some pics.

[MANUEL_MOUSIOL]

I just added some more together with some pics.

Thanks for the advice. I sorted it out via the import options but your tips sound great, although selecting the polygon groups and working on those like you said sounds like a looooot of work

[kosso_olli]

It isn't if it is done right after import with a script. But it makes your life a lot easier afterwards, because there is no edge overload in viewport

[MANUEL_MOUSIOL]

It isn't if it is done right after import with a script. But it makes your life a lot easier afterwards, because there is no edge overload in viewport

is there a script available for public? I dont know scripting at all...

[Moriah]

Usually when i import CAD data via abc/obj/fbx it comes as the 2nd picture you showed, and the only solution i've found is to exactly add an edit poly on top and it becomes like the 2nd picture. The ProOptimizer welding is a great tip!

[kosso_olli]

Usually when i import CAD data via abc/obj/fbx it comes as the 2nd picture you showed, and the only solution i've found is to exactly add an edit poly on top and it becomes like the 2nd picture. The ProOptimizer welding is a great tip!

That seems very odd. I would say something went wrong during the export. My experience is that Max is one of the best tools when it comes to data import, believe it or not. It eats everything out there. Try importing IGES/STEP in Maya, it's a nightmare.