topic Re: CAD Data - Detaching Polys & Smoothing Groups in 3ds Max Modeling Forum

CAD Data - Detaching Polys & Smoothing Groups

Anonymous — Mon, 15 Jul 2019 22:20:31 GMT

When working with CAD data I have to break up the model by detaching polygons.

However when I do this...

The new object created from the polys is totally messed up:

Smoothing groups have corrupted
Sometimes random holes

I've tried to go back in and sort smoothing groups out but can never achieve the same result.

Is there a way around this?

I'm having to use other 3D packages to break up and come back to max after - massive inconvenience.

Re: CAD Data - Detaching Polys & Smoothing Groups

dominique.bouthillette — Fri, 19 Jul 2019 21:30:10 GMT

Hi @Anonymous, thanks for the post!

From the image you shared it looks like there may be some intersecting edges, overlapping verts, or edges that do not create tris/quads (in the middle of an Edge), and things of that nature in the imported file. -- While the model may appear smooth as a whole object, topology can play a big part in how smoothing groups and object detachment is addressed. (The black areas that may appear in the model seem to be vertices without a connection point.)

In the past I have received STL files from companies (for projects) that have had similar issues due model topology. -- In these instances I usually use XView and STL Check to review any topo issues for revision.

I'm happy to take a look at a sample CAD file this seems to occur with if you can provide one, but I believe the above is why we are seeing this behavior: You can upload your file(s) here

For some additional background:

What version of 3ds Max are you using?
Where is the CAD data being exported from?

Thanks so much, and I look forward to your reply!

Re: CAD Data - Detaching Polys & Smoothing Groups

dominique.bouthillette — Mon, 22 Jul 2019 20:11:26 GMT

Just wanted to follow-up here to see if you were still experiencing this issue. Thanks!

Re: CAD Data - Detaching Polys & Smoothing Groups

kgokhangurbuz — Thu, 25 Jul 2019 07:22:41 GMT

Hello @Anonymous ;

It's because the topology of the object that's imported is not good.

There are multiple open edges, vertices and polygons that do not follow the ones next to them.

If you are importing this model just to render, try to use IGES format.

If you want to edit this, the object should be carefully modeled before importing, applying topology rules.