Use BIM files

ℹ️ Thank you prof. Rino for your contribution!

This wiki page shows a fast workflow to bring Building Information Modeling (BIM) data into BFDS, and export a valid FDS model.

It follows the steps from Prof. Rino’s video tutorial.

The goal is to start from an IFC model and finish with an FDS file you can run. If you do not have an IFC file, you can download an example from here.

BIM (Building Information Modeling) is a digital methodology for managing building information throughout its lifecycle, while IFC (Industry Foundation Classes) is an open, neutral file format and a standard that enables interoperability between different software in a BIM environment. IFCs describe the geometric and non-geometric characteristics of a building, allowing information to be exchanged between various software and multidisciplinary teams, supporting collaboration across the entire project lifecycle.

Overview of BIM data

BIM data gives you not only 3D geometry but also rich metadata for building elements. BFDS can ingest that geometry inside Blender and help you map it to FDS constructs.

The big advantage of this workflow is time. Instead of recreating geometry by hand, you convert and clean what you already have.

Note that FDS is voxel-based. You will export watertight, axis-aligned volumes that snap cleanly to your mesh resolution.

Prerequisites

The proposed workflow uses the following tools:

• Blender 5.2.0 or newer (the video was recorded with Blender 4.5.3, so some menus may differ)
• Bonsai (formerly BlenderBIM) — Blender extension for IFC import
• BFDS 7.2.x add-on
• FDS 6.11.x installed and runnable from your machine

All tools are open source and free to use.

Procedure

• Install the Bonsai extension in Blender. When in Blender, open the menu: Edit > Preferences > Get Extensions. Then search for Bonsai. Install the extension and enable it. Bonsai adds IFC import and BIM panels to Blender.
• Install BFDS. Please refer to the install page.
• Prepare an empty Blender Scene. Open a new Blender file, press A to select all default objects, and delete them by pressing the X key.
• Import IFC: File > Import > Industry Foundation Classes (.ifc). Pick your building IFC file.
• Navigate in the 3DView your imported geometry, and check the import looks correct.
• Organize and clean your file. Split the viewport. Set one side to the Outliner Editor to see the IFC hierarchy. Remove non‑essential IFC containers you do not need in FDS, for example: IfcSite, IfcSpace, furnishings. Keep structural and architectural elements that define volumes: IfcWall, IfcSlab, relevant IfcBeam/IfcColumn, roof, ...
• Confirm units are metres (Scene → Units).
• Create the FDS domain. In the BFDS panel, create or edit the MESH bounding box for the computational domain. Set IJK or DX/DY/DZ according to your chosen FDS mesh resolution. Ensure critical dimensions align reasonably with this grid to avoid stair-stepping surprises at export.
• Map BIM elements to FDS.

The following are the typical mappings between IFC and FDS items.

IfcWall, IfcSlab, IfcBeam, IfcColumn become OBSTs with appropriate XB selection (eg. Bounding Box or Voxel depending on the geometry of the element).

You can assign the XB property to one IFC item and use the BFDS Copy to operator to apply the same setting to the remaining IFC items.

IfcWindow, IfcDoor become openings. If you need the window or door to be closed, you can follow the previous step, assigning the OBST property to these items. If you want a specific door or window to be open, select the item and uncheck FDS OBST (Obstruction) in the Object Property Tab. These items will not be represented in FDS.

After mapping the relevant IFC items to the FDS namelists, you can export and run your case.

You can check the final geometry by running the FDS scenario and opening the output file in Smokeview from BFDS.

FAQ

Can I import Revit files directly?

Export from Revit to IFC first, then follow this guide.

Can I keep BIM metadata in FDS?

FDS uses geometric and surface definitions. Use the metadata to define a suitable SURF for your FDS simulation. The original metadata will not be used by FDS. You can remove it, or you can leave it as commented FDS code.

Does this workflow support multi‑storey models?

Yes. Consider separate domains per level if the full model is heavy. You can export level by level or create multiple MESH blocks.