topic Re: ArchiTurn (beta) — swept path analysis directly in Archicad: does the vehicle fit or not? in General discussions

ArchiTurn (beta) — swept path analysis directly in Archicad: does the vehicle fit or not?

catalinpopa — Sun, 16 Aug 2026 15:30:26 GMT

Hi everyone,

I'm an architect from Romania and I've been building a small add-on for a problem I kept running into: checking vehicle swept paths — fire-engine access, roundabouts, parking manoeuvres, garage ramps — without leaving Archicad.

WHAT IT DOES

- Swept Path (from Selected Polyline) — draw the intended path as a polyline, select it, pick a vehicle. You get the swept envelope, the driven path and the vehicle at start/end, plus a report: FEASIBLE / NOT FEASIBLE, minimum radius vs required, area, margins. If a corner physically doesn't fit, it refuses and tells you which vertex and how many metres are missing — it never draws a lie.

- Drive with Mouse — drive the vehicle through the plan with the mouse; what you see while driving is exactly the final drawing.

- Vehicles: car, van, rigid truck, city bus, and a semi-trailer truck with a live articulated trailer (jackknife detection included).

- Everything lands as ordinary Archicad elements, grouped — one Undo removes it.

HONEST CAVEATS — it's a closed beta: Archicad 29 28 27 26 / Windows only; vehicle dimensions are indicative presets (custom dimensions are the obvious next step); forward driving only; a KNOWN_LIMITATIONS document ships in the package with measured figures.

WHAT I'M ASKING: try it on a real case of yours and tell me — bluntly — whether it's worth investing more time in. Short questionnaire (10 questions, 5 min): https://forms.gle/yeEtTy4Roe7Y9TJp8 (the form is in Romanian — your browser's translate handles it, and answers in English are perfectly welcome) — or just reply here. Screenshots of anything wrong (the drawn line + the chosen vehicle) are the most useful thing you can send.

DOWNLOAD (zip: .apx + install guide + docs): https://drive.google.com/drive/folders/1bYL0_C88jD6-DZrYK0E9DG2pMv3DyuqZ?usp=sharing

INSTALL: copy ArchiTurn.apx into C:\Program Files\GRAPHISOFT\Archicad 29\Add-Ons\ and restart Archicad — the ArchiTurn menu appears.

Thanks — happy to answer any technical questions about the engine here.

Operating system used: Windows win11

Re: ArchiTurn (beta) — swept path analysis directly in Archicad: does the vehicle fit or not?

Miha Nahtigal — Sun, 16 Aug 2026 17:21:34 GMT

Turning curves have been addressed multiple times. Even cadimage had a free gdl object.

Why the addon - why not use plain gdl?

Re: ArchiTurn (beta) — swept path analysis directly in Archicad: does the vehicle fit or not?

Botonis — Sun, 16 Aug 2026 17:38:04 GMT

Autoturn from Transoft is only released for Revit and Autocad.

This addon has a lot of potentials to fill up the gap of real vehicle turn simulation.

We constantly design parking areas and we are not sure completely how they perform.

Those GDL objects available have limited options.

I am really interested in this addon and I can support any beta testing.

Great News @catalinpopa

Re: ArchiTurn (beta) — swept path analysis directly in Archicad: does the vehicle fit or not?

Lingwisyer — Mon, 17 Aug 2026 02:23:30 GMT

Single manauver turns are covered decently with the old CI objects and the new default GS objects. The main issue I find with these is that you cannot represent flowing turns cleanly, or do multipoint, so you end up drawing over them to get the end representation...

Re: ArchiTurn (beta) — swept path analysis directly in Archicad: does the vehicle fit or not?

catalinpopa — Mon, 17 Aug 2026 07:31:58 GMT

@Miha Nahtigal — fair point, and you're right that turning curves themselves aren't new. The reason for an addon rather than a GDL object comes down to what GDL can't reach:

A GDL object can only see its own parameters. It can't read a polyline you drew in the plan, follow it, and solve the trailer/rear-axle path against it. Swept-path analysis is an iterative geometric solve along an arbitrary input path — that's a computation, not a parametric shape.
Chained maneuvers (forward → stop → reverse → forward) need state carried between segments. GDL has no way to hand the end condition of one maneuver to the start of the next.
Interactive editing — drag the path, see the envelope update — needs the API. In GDL you re-enter numbers and regenerate.
Vehicle libraries (AASHTO / Austroads / EU design vehicles) and reporting on clearances are data + logic, not geometry.

So the GDL objects aren't wrong, they just stop where the interesting part starts.

Re: ArchiTurn (beta) — swept path analysis directly in Archicad: does the vehicle fit or not?

catalinpopa — Mon, 17 Aug 2026 07:33:26 GMT

Thanks, and yes please. Parking areas are the best possible test case, since that's where the multipoint and clearance issues actually bite. If you can share a couple of real parking layouts you've had trouble validating, that would help me make sure the solver handles the awkward cases and not just textbook geometry.

Re: ArchiTurn (beta) — swept path analysis directly in Archicad: does the vehicle fit or not?

catalinpopa — Mon, 17 Aug 2026 07:33:45 GMT

@Lingwisyer — that's exactly the gap I'm targeting. The CI and GS objects handle a single clean maneuver well enough, but flowing turns and multipoint are where everyone ends up drawing over the output by hand. Continuous path following and multipoint sequences are the core of what the addon does, not an add-on feature.