Convert imported polyface meshes from Archicad to 3d-solids

[3d-labor]

Hello everyone,

as one of my biggest clients moved from AutoCAD to Archicad I get dwg-files from Archicad, containing polyface meshes. These meshes represent, for example, a multi layer wall with plaster/insulation/concrete wall. I tried some of the hints of the forum to make 3d-solids out of it with no success. The elements look like the one in the screeshot. I have a dwg attached if someone want to see the structure. The IFC import from Archicad works only with AutoCAD Archtecture and lasts a very long time. The data I got then were useless. It would be enough for me when the 3d-solid contains only the outer limits of this polyface mesh.

[R_Tweed]

I'm wondering why you would like to convert these to solids?  Could you describe your intent for the objects?  Are you looking to extract bill of materials or use as a background? Solids may not be the best way to go.

[3d-labor]

Hello, I usually work with 3d-solids to build my models. I model it with AutoCAD and link the dwg to 3dsMAX. I get often 2d-dwgs from my clients and as I "grown up" with AutoCAD it is the easiest way for me to do the most of the modeling work there (I know, I could do it all with 3dsMAX). The problem with the data of ArchiCAD is, that it is too much information in these elements. There are 4 "physical" layers of material, but all on one "AutoCAD" layer. Sure, I can edit  polyface meshs with STRETCH and similar, but it is not convemient for me. I rather work with 3d-solids, which I can edit far easier (for example with 3d-strech from JMHsoftware). What I want is a way, to convert the polyface mesh shown in the picture to 3d-solids and then unite it to one 3d-solid. Or a lisp routine that searches the outer limits of an element like this and make a 3d-solid then. If you want similar to the "generate boundaries" command for hatches.  

[R_Tweed]

The lisp routine sounds interesting. You might want to try and post something to that forum and see what happens.  Do you use ACA for any modeling or are you trying to use it solely as a conversion utility?   The mesh supplied has overlapping faces and is not water tight which is not easy to convert. I think the conversion process would be longer than just modeling it. I tried a couple of different methods which you may have tried yourself and are listed below.

1. I opened the dwg in 3ds max and exported as a dwg. Then opened that mesh in autocad and tried to convert it which gave me errors.

2. I also exploded the mesh in autocad, converted to surface and then used sculpt to convert to solid which gave me errors.

3. You could use the elevation command in aca to get you the boundary your looking for but in my mind it seems counterproductive.

[3d-labor]

I use AutoCAD 2019 as modeling tool. As I mentioned I work with AutoCAD for a very long time (first used it 1989, and as apprentice since 1992 every day) So I´m somekind of old fellow who is not willing to change the way doing things if not neccessary. I think I´m quicker with modeling in AutoCAD than with 3dsMAX. In 3dsMAX I of course put all the assets in etc. The Archicad Model has this structure every time. I hope, that my client can manage another way to export it. I know that after exploding some of the 3d-faces are in the same plane. This is the difficulty for the lisp routines. I will visit my client to search for a better way to export it.

[R_Tweed]

might want to ask for an stl file.

I know that I can send my aca models to 3d print which outputs an stl file.  3sdmax will open stl and export to dwg if you do not have another converter.  When you open the dwg file in autocad the resulting mesh should be watertight, and can be converted to a solid or solids depending on how they did there export. 

archicad to stl 

[3d-labor]

Thank you for the tip. The problem with  stl would be, that you have to do it layer by layer to distinguish between the building elements. But I gave it a try. At first I tried to export from AutoCAD to stl. This doesnt work with polyface meshes. Then I exported the element from dwg to max and made a stl out of it. When I reload it to AutoCAD nothing happens. No error messages but also no imported element. The stl was ok because I was able to reimport it to max. So I once more imported the polyface mesh from AutoCAD into max and saved this one back to dwg. After I opened it in AutoCAD I saw it was a net now. So I used the SURFSCULPT command. It generated a 3d-Solid but not all parts of the net were converted. But with this 3d-solid can operate as normal with all the editing commands.

[R_Tweed]

You are quite right. I ran a couple of tests from revit to stl to 3dsmax to dwg with simple walls (no inlays) and was able to make solids. However, once I made a wall that had some complexity (inlays) Autocad would not convert the meshes as they had overlapping faces which is unfortunate.  I will have to see how these stl files print. Either way, it seems like quite an effort to convert all these elements rather than to use the imported model as a starting point to add solids or just re-model the building using familiar steps.  It's interesting that this problem is not new.(see post from 2004) I would think there might be a way using some other software that may or may not be out of your confort zone to, again make the conversion.  It just seems to me that the conversion would never be quite what your looking for in terms of elements and time spent.  Good luck though.