Showing results for 
Search instead for 
Did you mean: 
Showing results for 
Search instead for 
Did you mean: 
2024 Technology Preview Program

2024 Technology Preview Program:
Master powerful new features and shape the latest BIM-enabled innovations

Post your wishes about Graphisoft products: Archicad, BIMx, BIMcloud, and DDScad.

Subtract finishes with Solid Element Operations

Kevin -The Homesmith

Would it be possible to add composite element skin type recognition to the solid element operations?

One example use case is this… I’d love to be able to subtract wall finishes above a dropped ceiling slab element, but still let the framing pass through.


So basically, what I’m asking for is a “subtract finishes with upward extrusion” option.

I’m sure your team could make that happen and users would love you for it!

Laszlo Nagy
Community Admin
Community Admin

If I understand what you are trying to achieve, you can do that with Complex Profiled Walls and Modifiers (Parametric Profiles). With Modifiers you will be able to make the finish skins different height from other skins. Check out the use of Modifiers in the Help files.

Loving Archicad since 1995 - Find Archicad Tips at
AMD Ryzen9 5900X CPU, 64 GB RAM 3600 MHz, Nvidia GTX 1060 6GB, 500 GB NVMe SSD
2x28" (2560x1440), Windows 10 PRO ENG, Ac20-Ac27

As @Laszlo Nagy  suggested by using complex profiled walls and also with composite wall you can achieve this by making the ceiling outline peneteate the wall skins and stop at the inner edge of the finish skin then apply SEO and let the ceiling to be operator & the wall to be target with subtract with upward extrusion operation you can get your wish.

In complex profiled walls you will have to adjust skins heights if you changed the ceiling level but in this way you preserve subtracting wherever you move the ceiling.


Edit: you have to change the layer intersection group number for the slab to be different from the wall layer intersection group number to be able to subtract for example slab to be 2 while wall is 1.

AC 27 INT 5030/WIN 11
AMD Ryzen 7 5800H with Radeon Graphics 3.20 GHz 16.0 GB

For these purposes, I personnaly created some "empty" materials with different intersection prioritys, and totally transparents. One of them is called "empty without finishes". If I interesct this material with any element, it will erase the finishes layers of them. (Because all my finishes materials have a lower priority than this "empty")

One problem is that this material is transparent in 3D but still appears in sections or elevations.

One solutions is to place it in a non visible layer.


But more generally, it could be usefull to think about this question, How to erase the finishes of a composite in a specified space ?

For an other example, I would love this option for roofs. Could it be possible to stop the inside finishes of roofs at the reference line and just continue the structure and outside around it ?

Étienne - AC 24 - France

Capture d’écran 2023-04-18 112543.jpg

Here are the "empty" materials.

They just miss this option : "not visible in sections and elevations"

Étienne - AC 24 - France

Thanks, I've been meaning to explore those modifiers. I'm a user since v18 and I haven't updated my template to these new features. I suppose that's what I need to look into.

This is what I'm currently doing,

I am typically using my 3D slabs to show ceiling lines and occasionally even do reflected ceiling plans. If I trace the slab around walls that extend past the ceiling, I end up with ceiling lines on the plan that I'd rather not show. Particularly at doors. 


This is an interesting workaround, but specializing materials for particular instances becomes really cumbersome. I have so many composites in my files, it's getting ridiculous. I maintain that making SEO recognize skin types would be a great way to simplify things for us and it also seems like it would be relatively easy to implement.