IFC from a 2D floor plan: walls, doors, windows and rooms read from a DXF

What it reads

Two more figures, for the larger plan: Clinic, floor 1 and Clinic, floor 2 (each a few hundred KB).

How well it reads

Each plan was cut from a published IFC model at 1.2 m above the floor by tools/recognize/plan_dxf.js, and written as a DXF on the usual AIA/NCS layers (walls, doors, glazing, columns, room outlines and names), the kind of drawing a design office hands an owner. The recognizer reads it back and tools/recognize/score.js compares what it found with the model.

• Wall overlap is the intersection over union of the wall area the software found and the wall area in the model, on a fine grid: 1.00 means the two are the same. Wall area found is the share of the model's wall area the recognized walls cover. Measured 2026-10-24 with docs/launch/site/capture_drawings.js (method).
• Doors and windows found counts the model's doors and windows that have one recognized within 0.5 m, of the same kind; of those found, right is the share of recognized ones that match one in the model. On floor 1 of the Clinic the 2 it missed are 2.7 m chain-link double gates set in a curtain wall, which is drawn as single lines and not read as a wall. Measured 2026-10-24 with docs/launch/site/capture_drawings.js (method).
• Rooms from walls alone is the mean overlap of each room in the model with the room traced from the walls, with the room-outline layer removed from the drawing. With that layer present the mean overlap is 1.00, 1.00, 1.00, 1.00 on the four plans, in the order of the table. Level 1 of the Duplex scores 0.40 because its living, dining and kitchen are one open space with no walls between them: the model divides it into rooms that a plan without room outlines does not show. Measured 2026-10-24 with docs/launch/site/capture_drawings.js (method).
• The Clinic model has 5 doors on floor 1 modelled twice in the same place; each pair is counted once. Measured 2026-10-24 with docs/launch/site/capture_drawings.js (method).

The model it builds

tools/recognize/dxf_to_ifc.js builds an IFC4 model from the drawing alone: one wall type per thickness found, walls on their centre lines, doors and windows hosted in them, a space for each room and a floor slab on the outline. It reads the file back and checks it against the EXPRESS rules of the schema.

A floor plan has no heights. These are assumptions, written into the model's project description: stories 3 m, doors 2.1 m, windows 1.5 m from a 0.9 m sill, slab 0.2 m. Gaps in a wall with no door or window drawn in them stay gaps in the wall. Materials are recorded as unspecified. The Clinic's floor 1 has no windows because its glazing is curtain wall, which the recognizer does not read yet. Any element the builder refuses is listed in the script's report with the reason; none was refused on these plans.

The rebuilt model in 3D

Both Duplex plans, and both Clinic plans, rebuilt as one IFC4 model per building from the drawings alone and drawn by NativeBIM's geometry engine. The "Duplex apartment" tab is the model the plans were cut from, so you can compare the two. Drag to orbit, use "Story by story" to step through the levels, and click an element to read what the drawing gave it. The heights are the assumptions above.

The 3D view loads when it scrolls into view. It is the 3D viewer with these models; the rebuilt models are built by docs/launch/viewer/build-viewer.js with tools/recognize/dxf_to_ifc.js. Models: BSI (2020) "Duplex Apartment Test Files," buildingSMART International, CC BY 4.0 and BSI (2020) "Medical-Dental Test Files," buildingSMART International, CC BY 4.0; cut to DXF floor plans by NativeBIM, rebuilt as IFC4 from the drawings and converted to glTF. NOT FOR CONSTRUCTION.

What it does not do yet

• Curved walls are reported and skipped; a curtain wall drawn as single lines is not a wall pair and is not read as one.
• Layer names are read by the AIA/NCS convention and common variants (A-WALL, WALLS, A-GLAZ, WINDOWS). A drawing with every line on one layer is not read.
• Scanned drawings and PDFs are not read: the input is a DXF with real lines. Plans exported from another program have not been scored here, because there is no published set of such drawings with a model to compare against.
• One story per drawing. Stairs, furniture and dimensions are ignored.

Models

• BSI (2020) "Duplex Apartment Test Files," buildingSMART International, CC BY 4.0. Changes made: cut to a 2D floor plan by NativeBIM, read back and rebuilt. Source repository
• BSI (2020) "Medical-Dental Test Files," buildingSMART International, CC BY 4.0. Changes made: cut to a 2D floor plan by NativeBIM, read back, re-planned as office space. Source repository
• The warehouse is generated by NativeBIM (tests/authoring/builder/warehouse_sample.js).

Reproduce it

node tools/corpus/fetch.js --id community-duplex-arch
node tools/corpus/fetch.js --id community-clinic-arch
node docs/launch/site/capture_drawings.js
node tools/recognize/plan_dxf.js corpus/community-duplex-arch/<file>.ifc --storey "Level 2" --out level2.dxf
node tools/recognize/dxf_to_ifc.js level2.dxf --report level2.json

docs/launch/site/capture_drawings.js writes docs/launch/site/data/drawings.json and the figures; --check confirms they are current. Recognition is deterministic: the same drawing gives the same walls, and the same model GlobalIds.

Notices