ArchiCAD PLN — Graphisoft's BIM format: one of the oldest BIM platforms for architects

2026-06-1710 min read

BIMarchicadgraphisoftplnplamodbimxarchitecture

Export formats: ARCHICAD-PLN

ArchiCAD is one of the oldest fully-fledged BIM platforms in the world, born in Budapest back in 1984 — a decade earlier than Revit. Its native format .pln stores a complete building information model: wall geometry, slabs, roofs, windows and doors, multilayer composites, room schedules, library elements, and rendering parameters. Alongside PLN live extended siblings — .pla (archive with embedded library), .mod (reusable module), .bimx (hyper-model for presentations), and .tpl (project template). For an architect designing a building on a specific site, OSM map context with neighboring blocks and streets becomes as important as the model itself — and that's where osm2cdr.ru closes the gap through DWG, DXF, and IFC export.

Map generation of Prague city center — Prague Castle, 200×200 m. Prague — a Central European city culturally kin to Budapest — features the kind of historic fabric that local architectural offices have modeled in ArchiCAD for decades.

History: a Hungarian DOS startup that beat Autodesk by a decade

In 1982 in Budapest a small team led by Gábor Bojár and István Tari — both trained physicists — set out to build software that would work not with flat drawings but with a three-dimensional building model. In socialist Hungary getting Western computers was hard, and the first version of ArchiCAD (then called Radar CH) was written for the Apple Lisa in 1984. By 1987 the team had bought the prototype back from the state, founded Graphisoft, ported the product to Macintosh, and shipped ArchiCAD 1.0 — the first commercial 3D building CAD in existence.

Through the nineties ArchiCAD set the tone in many ways: GDL (Geometric Description Language) for parametric library elements appeared in 1986 — 13 years before Revit Families. Full-featured IFC export — in 2001, in the very first IFC 2x specification. Multi-user collaboration support (Teamwork) — 1996, initially via file shares, then a dedicated BIM Server, and finally BIMcloud in 2014.

In 2007 the Nemetschek Group (the German conglomerate that also owns Allplan, Vectorworks, and Solibri) acquired Graphisoft and kept it as an independent product hub in Budapest. As of today — May 2026 — the current version is ArchiCAD 28, with annual releases. Per Graphisoft's own data, ArchiCAD holds approximately 25% of the global BIM-for-architects market, dominating in Hungary, Germany, Austria, Japan, Italy, and post-Soviet countries. In Russia ArchiCAD has historically been used by Mosproject, Studio Meganom, the Tsimailo, Lyashenko & Partners bureau, SPEECH, and dozens of regional offices.

What's inside the file: PLN, PLA, MOD, BIMx

The .pln format is a binary container with a proprietary Graphisoft structure, versioned per ArchiCAD release. Reading it without ArchiCAD itself is practically impossible — there is no backward compatibility even between major versions (ArchiCAD 27 won't open an ArchiCAD 28 file directly, you need Save As Backwards). Inside PLN sits a tree of model objects: walls with wallType, referenceLine, composite (multilayer build-up), slabs, roofs, beam grids, stairs. Each object carries geometry and attributes: material, layer, ID, classification per UniFormat or OmniClass.

Library elements (windows, doors, furniture) are either built-in GDL objects or references to external libraries. This is the key difference between PLN and PLA: the former references libraries on the user's disk (if the recipient lacks them — doors won't render), the latter stores a copy of all used libraries inside the file. So when handing off a project to a contractor, architects usually save as PLA — it's the equivalent of a project "ZIP archive".

The .mod format is a module, a separate mini-model of several objects that can be inserted into any PLN project. The nearest Revit analogue is Family, but a MOD can contain not only parametric families but entire typical apartment layouts, joinery details, or façade fragments. Large architecture firms maintain internal libraries of MOD files for typical solutions.

.bimx is the "hyper-model" — a special presentation format opened by the free BIMx Desktop Viewer or mobile apps for iOS/Android. BIMx compresses geometry into a GPU-optimized format and binds the 3D view to navigation by 2D drawings — the client clicks on a room in the plan, BIMx shows the interior view.

Who needs the format: five roles

Architect in a private practice. Residential houses, small-scale commercial buildings, historic-building reconstruction — ArchiCAD's bread and butter. The intuitive interface and the absence of schizophrenia between "architectural" and "engineering" workspaces (which Revit has) makes ArchiCAD the choice of small studios where one architect leads a project from concept to construction documents. A PLN file is the single source of truth for the whole project.

Architect in a large bureau with Teamwork. When 10–30 people work on a single building, a PLN file becomes a Teamwork project hosted on BIMcloud. Each architect reserves a layer, a room, or a specific object, edits locally, then commits back. The result is a distributed version-control system on top of the BIM model. This is a separate discipline with its own quirks, and Graphisoft offers dedicated training for it.

Architecture school professor. Graphisoft has historically provided free student and educational licenses, and in Russia ArchiCAD has been taught at MArchI, GUZ, and SPbGASU for decades. Young architects enter the profession with PLN skills. Professors typically work with student projects in PLN and then export portfolios to BIMx for online demonstration.

Investor client without CAD skills. BIMx Mobile Viewer is a free iPad app where an investor rotates an apartment model with a finger, walks through it in "Walk Mode", inspects layouts. Many premium-segment developers in Moscow and St. Petersburg include BIMx demonstrations in marketing — the client sees a future apartment before the building is delivered. Technically a non-working but commercially critical scenario for the PLN universe.

BIM coordinator on a mixed project. On a large building, part of the models are made in Revit (e.g. MEP), part in ArchiCAD (architecture). The BIM coordinator merges everything in Solibri Office or Navisworks via IFC. PLN exports to IFC2x3 or IFC4 — that's the point where ArchiCAD interfaces with the rest of the BIM world. Graphisoft's IFC export quality is historically considered one of the best in the industry, outperforming Revit in geometric accuracy.

Software for ArchiCAD: seven programs

Graphisoft ArchiCAD. The only program that opens and edits PLN fully. Paid subscription through certified resellers. graphisoft.com/archicad

BIMx Desktop. Free viewer for BIMx hyper-models. Doesn't open PLN directly, but an architect can export any PLN to BIMx and share a link. Cross-platform — Windows, macOS, iOS, Android. graphisoft.com/bimx

BIMcloud. Graphisoft's server product for Teamwork scenarios. Separate subscription from ArchiCAD. Cloud or on-premise. graphisoft.com/bimcloud

Twinmotion. Real-time architectural visualization on Unreal Engine, owned by Epic Games. Imports ArchiCAD projects via a direct plugin — select "Send to Twinmotion" in ArchiCAD's menu, a synchronized model opens. Basic version free. twinmotion.com

Lumion. An alternative architectural-rendering engine popular among Russian architects. Import via FBX from ArchiCAD or a direct LumionLiveSync plugin. Paid subscription. lumion.com

Solibri Office. A Dutch (now Nemetschek) tool for BIM model quality checks — clash detection, code compliance, BCF issue export. Works with IFC rather than PLN, exported from ArchiCAD. solibri.com

PARAM-O. Visual programming for ArchiCAD on nodes (node-based), an analogue of Dynamo for Revit or Grasshopper for Rhino. A free Graphisoft application extending GDL for parametric modeling. graphisoft.com/products/param-o

Pitfalls and tips

No backward compatibility. ArchiCAD 27 won't open a file from ArchiCAD 28. If working with a contractor on an older version, you must use Save As and explicitly select the target version. Graphisoft supports back-saving up to 3 versions, beyond that — IFC export and model rebuild.

A PLN without libraries breaks. If a recipient opens a PLN referencing libraries they lack (e.g. your custom doors, or Graphisoft Library 28 while they have 27 installed), the model renders with "Missing Library Parts" — big red dots instead of elements. Solution: always hand off as PLA (with embedded libraries), or separately ship an LCF library archive.

BIMcloud Teamwork requires discipline. In distributed work the classic mistake is forgetting to release reserved objects. They stay locked for colleagues. Office workflow typically requires release at end of day. The project manager can forcibly take over a lock via BIMcloud Admin.

ArchiCAD's IFC export is the gold standard, but it's configurable. When exporting via File > Save As > IFC, pick the right MVD (Model View Definition): IFC4 Reference View for coordination, IFC2x3 Coordination View for a contractor on older software, IFC4 Design Transfer View for round-trip exchange. The wrong MVD breaks geometry on the receiving side.

Coordinates in ArchiCAD are a separate matter. Unlike Revit, ArchiCAD has two concepts: Project Origin (internal model reference point) and Survey Point (geodetic site anchor). When importing DWG from osm2cdr.ru, alignment with the Survey Point is critical — otherwise the model ends up several kilometers off-site after IFC re-export.

Site Modeler for terrain. ArchiCAD has a built-in Mesh tool for terrain modeling. If you fetch SVG or DXF contour lines from osm2cdr.ru, you can use them as reference lines for Mesh. For flat urban sites terrain isn't needed — a 2D DWG underlay as Trace Reference suffices.

How to do it via osm2cdr.ru: workflow and snippet

There's no direct PLN import from osm2cdr.ru — it's an ArchiCAD-specific format requiring the program itself to generate. But osm2cdr.ru closes a critical step in an architect's work: getting site context in formats ArchiCAD understands.

Step 1. On osm2cdr.ru outline the site and its surroundings — usually 200×400 m for urban infill, 800×800 m for a suburban estate. Step 2. As format pick DWG (for 2D plan underlay) or IFC (for 3D context of neighboring buildings). Step 3. Download. Step 4. In ArchiCAD open your PLN and run the import.

For DWG underlay as Trace Reference:

File > Interoperability > DWG/DXF > Place External Drawing
  > pick map.dwg from osm2cdr
  > Translator: "Geometric"
  > Layer: place into a dedicated "Site Context (OSM)" layer
  > Origin: Project Origin or an explicit reference point

For 3D context via IFC:

File > Interoperability > IFC > IFC Hotlink
  > pick map.ifc from osm2cdr
  > position by Survey Point
  > Visibility: Reference Only (non-editable)

Programmatically via Python and the ArchiCAD External Reference API:

# ArchiCAD has a JSON API (Tapir / Archicad Python API)
# Example: auto-publish the model after context import
import requests

archicad_api = "http://localhost:19723"
payload = {
    "command": "API.Publish",
    "parameters": {
        "publisherSetName": "Final Submission",
        "outputPath": "//server/projects/PRJ001/output/"
    }
}
response = requests.post(archicad_api, json=payload)
print(response.json())

Once the OSM context is underlaid, the architect models the building in PLN and finalizes via Publisher Set — a batch export to PDF (drawings), DWG (for the contractor), IFC (for BIM coordination), BIMx (for the client), and Twinmotion (for renders).

Sources

Graphisoft ArchiCAD Reference Guide, current version — graphisoft.com/resources-and-support/reference-guide
ArchiCAD File Format History (Graphisoft Help Center) — helpcenter.graphisoft.com
buildingSMART IFC Specifications — technical.buildingsmart.org/standards/ifc
Tapir — Archicad JSON API community library — github.com/ENZYME-APD/tapir-archicad-automation
BIMx Format Description — graphisoft.com/bimx
Nemetschek Group corporate profile — nemetschek.com