3dsmax STEP import question

[samuel_bubat]

Is there any way to prevent max from welding surfaces when importing STEP files directly as mesh ?

[kosso_olli]

Well, Max never welds anything on import of Step files. If surfaces are welded, they were joined in the native Nurbs software before exporting as Step. Nothing that can be done about this.

[samuel_bubat]

What I mean is. When you import with max native importer directly as mesh, select one object and go to subobject level "element" it will select the whole object as if all the surfaces are welded. I think it' s called sewed with nurbs. When you do the same with power translator or import as body objects with max native importer you can select individual surfaces on subobject level element. Our plan was to use the max STEP importer and no longer use Power Translator after we upgraded to 2019. Well I could just import as Body objects and convert the objects to mesh. But this is where my problem starts. When I select all objects, add an editable mesh on top I have two options to collapse. With "collapse all" it works but instances are lost. when I collapse with "collapse to" instances are preserved but some weird things happen. Random objects disappear and become instances of other objects. I tested with several STEP files and it happens with all of them. I thought there might be some option not to sew surfaces on import when importing directly as mesh. I had in mind there was some config file for the importer. Meanwhile I kind of found this config file. It' s still in max but belongs to the old aruba importer wich was replaced. So for the moment it looks like we need to stick with power translator.

[kosso_olli]

As I said, Max does not weld any surfaces on import. If the imported parts show that behaviour when selecing elements, the surfaces were already joined in the software the data is coming from.

[samuel_bubat]

I can't say if it was welded in the CAD software in advance. But presuming it was welded or joined in the CAD software I would expect a surface to be welded when importing as body objects as well. This is not the case. Attached are two screenshots. Both show a simple imported part. The right one directly as mesh. The left one as body object and converted to mesh. On the first screenshot you can see the whole object beeing selected when selecting something on element level. On the second an individual surface can be selected on element level. When importing with PowerTranslator or the old aruba importer in max2014 I get the same behaviour as in the second picture. I tried this now with a dozen different STEP files it' s the same behaviour for all of them. To me it looks like max automatically sews surfaces on import as mesh and there seems to be no option to prevent this behaviour.

[kosso_olli]

To me it looks like max automatically sews surfaces on import as mesh and there seems to be no option to prevent this behaviour.

It doesn't. I'm importing Step and Iges from Catia just fine. As I said, when the surfaces are already joined in the Nurbs software, you are screwed if you want to use the parts as mesh. No idea why it is different when using the body objects, but I won't touch that with a stick since I had a very bad experience some years ago. Max's importer is just fine. You can say what you want, but actually Max's capability to import nearly every file format out there is actually quite good.

[thablanch]

When you use 'import as mesh' 3dsMax will weld the faces together, nothing to do about this. However, the Elements will remain.
kosso_olli, can you explain your workflow for 3dsMax 'not to weld things' when importing, that would be appreciated
To avoid this, import with ' non mesh elements, it will import a body object, after, edit that body object and collapse it to mesh.
In the Editable Mesh object, the different elements will remain, you can select them, The previous faces now become elements
Our workflow is based on body objects, and it works better, is mode flexible and way lighter than using the collapsed method.

[samuel_bubat]

When you use 'import as mesh' 3dsMax will weld the faces together, nothing to do about this. However, the Elements will remain.
kosso_olli, can you explain your workflow for 3dsMax 'not to weld things' when importing, that would be appreciated
To avoid this, import with ' non mesh elements, it will import a body object, after, edit that body object and collapse it to mesh.
In the Editable Mesh object, the different elements will remain, you can select them, The previous faces now become elements
Our workflow is based on body objects, and it works better, is mode flexible and way lighter than using the collapsed method.

This is what I did. Import as body and afterwards collapse to mesh. But this brings up the problem that when I uses "collapse all" instances are lost and when I use "collapse to", as I wrote, it does weird things and random objects disappear. For the moment we will upgrade our Powertranslator Licenses, wich I tried to avoid as apart from the autowelding the max importer is pretty good. I brought this issue up at the Area forums and an Autodesk employee stated he is aware of this problem, customers he' s looking after have the same problem and that I should make a feature request. This is what I did. I wonder why there is no solution allready. I would think it should be not a big deal to make checkbox not to weld vertices on import.

https://forums.autodesk.com/t5/3ds-m.../idi-p/8329840

[thablanch]

Random objects disappear.. You have a step file you can share ?

[samuel_bubat]

I just wanted to make you some screenshots for you but right now I can' t seem to replicate it. I tried with a lot of different files the last days and it always happend. Basically what happend was. Import STEP as Body, select all, add an editable mesh, right click editable mesh "collapse to". Random objects disappeard. Well they were not deleted. They were still in the scene but they became instances of other objects in the same position as the other object. Pretty weird.

But, well, after all I have to import something like 100+ STEP files each year. So I don' t want to be forced to use to many workarounds. Basically why I started this thread was to ask if there is some sort of config file like there was in the old importer to turn the autoweld off. This does not exist. So until there is a fix for this I will stick to Power Translator wich does a good job. Thank You for trying to help me out !

[pokoy]

The ATF importer (the new one) is a black box, unfortunately, nothing is exposed.

The disappearing geometry with Body imports doesn't sound very good. If you come across this again, make sure to either report, it needs to find its way to Autodesk.

Missing faces/patches, trimming leftovers and similar geometry issues or accuracy problems with joined surfaces are relatively common with Body Objects, unfortunately. If you try to fix those issues on Body Object level, there's no undo and it tends to crash. On the other hand, it supports object referencing and doesn't weld so it's easier to select mesh elements. And of course, the ability to tessellate on the fly is its main advantage over ATF.
However, the problem is that the library is a few years old already. It's licensed from nPower but it's not kept up to date with their plugin version which does a much better job. If you find that Body Objects do a bad job, consider buying the PowerTranslator plugin from nPower, I'm pretty sure it'll perform better.

ATF on the other hand does a better job at importing and tessellating problematic files but since its tessellation options aren't exposed you may end up with a crazily high mesh resolutions, or way too much faces in one place and too few in other areas. And it welds stuff for no reason, making it really hard to select parts of the mesh.

It's a bit disappointing in that we have two solutions and each of them has a weak point with the potential to drive you crazy and cause troubles.

[kein_plan]

npower does a very good job. if you have to deal with 100+ files, it is really useful.