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Modelling and drafting in ARCHICAD. (Example: How can I model a Roof soffit/fascia?)

Moderators: ejrolon, Barry Kelly, Karl Ottenstein, LaszloNagy, gkmethy

This question has come up a few times from clients: how to create an arched opening in a curved wall? (Or a curved wall with an arched top, or an adobe-style ornamental top...)

I tried using the Arched Top Door Opening (door) but it cuts in a straight extrusion, rather than splaying around the radius. While this may be OK for very gentle curves, it doesn't work well for tighter curves.

In the past, on a consulting basis, I have laid out a shape as a slab, then saved as a library part and changed the script to use BSLAB ("bent slab") instead of CSLAB. It's not that hard if you know GDL, but it's cumbersome and requires very careful editing.

Does anyone have any other ideas for how to approach this geometric challenge? Any library parts out there that could be used with Solid Element Operations to cut the hole?

FYI - I searched the standard library shapes and nothing will do the job. The conoid object is closest, but the compound curve for an arch in a curved wall does not actually follow a conical path.
Hi, Bobrow,
For the arched opening on a curved wall, I use the Arch Top Door Opening, just change the option "Opening Side in Curved Walls" to Radial. This works fine for me. At least for the arched openings in curved walls.
And for the top arched curved walls, I use shells. I make the shell straight first, then define contour, then curve the segment I need.

This method has some limitations but it has helped me a few times.
This is a shell in the Pic.

PD: I have learn a lot from your tutorials!
Thank you so much arqrivas!

I hadn't noticed the Radial option on the Arch Top Door Opening - that does the trick! It also has a resolution parameter, which can really help make the curve quite clean.

For top arched curved walls, I can see that your approach gives a reasonable approximation, although the top is slanted rather than perpendicular to the wall face.

I found I was able to create a very clean arch top curved wall using solid element operations. The operator is a wall with the arch top opening you suggested, but in this case it is used in a different context; the wall with arched openings is able to cut off the top of the target wall very nicely!

You'll see two examples of this in my screenshot - one smaller and one more extended arch, alongside the shell that I created using your approach.

(I'm showing Trimming Bodies in the On-screen View Options to be able to visualize the shell contour more easily.)
Arch Top Curved Walls.jpg