Geometry problem - wall with window holes


Hi everyone,

I imported a simple building geometry from Archicad (here is only one wall as an example) and I don’t know how to solve this issue in a simple way. In the first picture the wall is shown, in the second, if I move a vertex, there is a weird polygon in the back meaning that there’s something wrong and the vertex doesn’t belong to the edge I’ve moved it from. The wall has 0 thickness, so there’s no back polygons - IF I edit poly and click on the wall to select polygon, there is only one, after deleting it, the wall disappears.

If I select all vertices and let the Max weld them, it doesn’t help.
I can’t leave this geometry this way as when I import the file to Perpakura software as is, it cannot handle unfolding geometry in the right way - there’s no windows in the final effect.

I know I could cut the polygon to support each vertex, but it’s too much work.
I need to have it done in all walls (quite many of them). Is there any quick way to solve this problem?

Thanks in advance.



Yeah that can happen from programs that don’t care about model topology
A more ideal topology would be to have a line connecting all corners of each window to the closest corner of another window and then to the sides–like in a grid. Or having a line go down in the space between windows and the corners connecting to the intersections. You can use tools like Quick Slice to add some edges.


darthviper, yes, slice works ok, but as I said - I have multiple walls like the one here, and adding edges to polygons manually will take forever.
I’m looking for a solution that could work on the whole object. Plugin, or some specific way of importing geometry…


There’s nothing that’s going to do it automatically, that’s the result you get when you try to cut a bunch of holes in a single polygon.
If you aren’t going to move the vertices around then the issue shouldn’t be too apparent though you might get problems with UV’s. If you export to some other software or game engines then it might triangulate things wrong and you’ll get edges crossing through the windows.


Ehh, I really don’t like this answer :wink:
It’s not possible neither by saving in a specific way nor by a specific file type?


Can you export as obj, on import select ‘triangulate geometry’

edit: that wont work on import Im sure…, maybe better to export to a format that lets you triangulate


Turn to Poly modifier, keep polygons convex

You can triangulate it with same mod. if you want.


Domos thanks, but it’s not clear to me. You mean 'turning it to ‘editable poly’ ? How do I keep polygon convex, should something be turned on?




Ok, found it thanks, but it doesn’t seem to help.


That’s the only way it can try to connect things without adding more vertices, but it wouldn’t know where to add vertices


I am pretty sure "The wall has 0 thickness" is the problem…


I am pretty sure you are wrong.


i know for sure, what domos suggested, did not work, so…
Give it a try!


I think ‘0 thickness’ is not the problem as there’s no backfaces, and polygons don’t overlap.
I’m really suprised, this is not easily solvable. It’s a very basic thing…this type of a problem rather looks like a continous bug. few holes in a surface and Max doesn’t know how to handle geometry properly, really?


I installed ArchiCad and checked it. You were right, the 0 thickness is not the problem.

But this is not a bug of Max, or Max not knowing how to handle geometry but, the lousy geometry export of ArchiCad. I tried 3ds, dxf,dwg, it´s all not usable

I`ve been working with architects for 20 years and every time i get geometry from Archicad it sucks!
Archicad does not build geometry as we would like it in Max.

I can´t really handle Archicad; but i tried following: i drew the wall´s outline and the windows in 2d in ArchiCad and applied an Edit Poly to the Editable Spline in Max.
This produces clean flat geometry, but i don´t know if this also works for you on a large scale…


cgjack, thanks for spending time on it.
I’d rather say that these program are not compatible with each other, not that either creates geometry in a correct or bad way. Archicad makes it properly in its on way, many people use it with success. It’s just very strange that the same, VERY simple geometry, causes problems in different programs.


There’s issues trying to convert NURBS geometry from CAD software to programs like 3ds Max that use polygons, they’re not too concerned with topology.


No problem in / with different programs.
The problem here would be to expect one program to just do things the way someone wants it to.
Even if that is not the correct, expected way.
(Expected when you know how things works)


Wow! (-;