MoI > 3DS Max workflow (normals problem)

mantaskava

Hello everyone,
Can anybody please explain me what is going on here? It seems like Max is destroying MoI's normals immediately after I modify the geo or even place a simple edit poly modifier on top. Does this mean it's not possible to modify/continue the work I started in MoI, later in Max or I am doing something wrong here? It would be very disappointing to know that this workflow has a major flaw like this.

Object was exported from MoI with Ngons checked as an FBX and imported to Max with Smoothing Groups unchecked.
I have attached original FBX file, too.
Wireframe:


Object straight after import (not modified):


Object after applying an edit poly modifier:


Object with modified geo (added cut):


Any ideas how to avoid this or fix this?
Any tips & tricks appreciated! Thanks.

musashidan

5 seconds after opening your file I spotted all the broken/mismatched topology. Look closely at the mesh. The edgeloops around the curves of the internal cutout haven't converted properly to polygon geometry. How did you miss this?

As for the mesh going black. This is a surface shading error caused by the MASSIVE N-gon. A few strategic cuts will sort that out.

You will have to revisit your MOI export settings(I don't use it so can't help there)

Noors

Well yeah you're destroying your custom normals when you edit the geometry.

This is an issue i had with CAD models needing some fixes aswell.

The easiest way to fix this would be to use, after your edits, any face weight normal script like this :

http://www.bytehazard.com/articles/wnormals.html

(You need to have 1 smoothing group for all object for this one to work)

And you could reset all your custom normals at import (with smoothing group option on), or with an edit normals modifier, so that you don't get black faces while editing (but you wet get the correct shading either)

Just tested and it doesnt like the "misaligned" verts in the center hole. Yeah that's not a very clean geo.

Depending of how much you edit the object, you could use a script to transfer vertex normals from a fresh imported mesh to the edited mesh:

http://www.scriptspot.com/3ds-max/scripts/noors-normal-thief

That's what i made to resolve the issue on heavy CAD models. But basically the shape was the same, just adding/removing cuts.

There's an other option which is storing the normals to a uv channel, and restore once edited. But it won't work if you destroy the uv while editing. And i don't have the script here.

mantaskava

Thanks for your answer Musashadin!
What do you mean by "not properly converted to polygon geo"? You mean that they are ngons?
Okay I've exported another version with only quads + triangles (file attached), and after applying edit poly normals break anyways.
And even if it didn't break, ngon geo would be alot easier to alter/modify than this triangulated mess.
The thing is, I hear people modeling stuff in MoI and then exporting to another software all the time, to either render it or work on it further. If it's only for rendering then there's no problem, but as as soon as you try to modify geo, it all falls apart.
So basically my question is - do all these people export with quads + tris ONLY (which means it becomes a headache to further work on it), or no one is actually modifying their geo in Max, and they export only for rendering.
Or am I missing something here?

musashidan

Your object from MOI is a NURBS solid object that gets converted to polygons at export. You may have to fiddle with the settings to get a cleaner conversion. No, the n-gons are fine. It's the misaligned/unwelded verts/edges that are the export error.

If you're just exporting for rendering then polysoup geo or any geo is fine. As long as the smoothing/surface shading is good. Personally I think it's a waste of time if it's just for rendering. You can get the same/faster/easier results using a rounded edges shader at render time. You can just mash/kitbash/boolean geo together to your heart's content and pick up those nice bevels in the shader. Max's native Arnold renderer has a rounded edges shader.

Anything you can do in MOI you can do in Max just as fast, without the import/export step and with 100% control over your geo.

mantaskava

Noors said:

Well yeah you're destroying your custom normals when you edit the geometry.

This is an issue i had with CAD models needing some fixes aswell.

The easiest way to fix this would be to use, after your edits, any face weight normal script like this :

http://www.bytehazard.com/articles/wnormals.html

(You need to have 1 smoothing group for all object for this one to work)

And you could reset all your custom normals at import (with smoothing group option on), or with an edit normals modifier, so that you don't get black faces while editing (but you wet get the correct shading either)

Just tested and it doesnt like the "misaligned" verts in the center hole. Yeah that's not a very clean geo.

Depending of how much you edit the object, you could use a script to transfer vertex normals from a fresh imported mesh to the edited mesh:

http://www.scriptspot.com/3ds-max/scripts/noors-normal-thief

That's what i made to resolve the issue on heavy CAD models. But basically the shape was the same, just adding/removing cuts.

There's an other option which is storing the normals to a uv channel, and restore once edited. But it won't work if you destroy the uv while editing. And i don't have the script here.

I guess this face weight normal script you mentioned is pretty much the same as this http://www.scriptspot.com/3ds-max/scripts/improved-face-weighted-normals ? Because that's the one I'm using. It fixes some areas but not all of it (like shown in the screenshot):


And two other methods sounds complicated and with their own limitations as well.
To me it sounds like there's still no way of modifying CAD models in Max hassle free.

mantaskava

musashidan said:

Your object from MOI is a NURBS solid object that gets converted to polygons at export. You may have to fiddle with the settings to get a cleaner conversion. No, the n-gons are fine. It's the misaligned/unwelded verts/edges that are the export error.

If you're just exporting for rendering then polysoup geo or any geo is fine. As long as the smoothing/surface shading is good. Personally I think it's a waste of time if it's just for rendering. You can get the same/faster/easier results using a rounded edges shader at render time. You can just mash/kitbash/boolean geo together to your heart's content and pick up those nice bevels in the shader. Max's native Arnold renderer has a rounded edges shader.

Anything you can do in MOI you can do in Max just as fast, without the import/export step and with 100% control over your geo.

IMO there's lots of situations where CAD modeling is superior to Poly/Subd modeling and vice versa. And since I have a lot more experience modeling in CAD from my engineering past, I just wish I could put that experience into use in arch-viz field as well.

Noors

Yeah for your case, transfering normals is the best way.

No there's no hassle free way. It's 2 different worlds. You'll always have custom normals derivated from nurbs curve. Either you just use the object with no editing (or you edit in the cad software) for rendering for instance, or you mess with custom normals and its limitations.

There are now polygon non destructive workflows that mimic CAD workflow : booleans, quad chamfer, round edges shaders, zbrush pass...which gives the best of 2 worlds. If you don't have to deal with micron accurate CAD files for industry, i wouldn't bother. You can make this object in 5 minutes in max with easier editing options.