AutoCAD to IFC Conversion Using the New IFC Writer

Introduction

This example uses FME Workbench to convert 2D rooms from a CAD floor plan to 3D Spaces in IFC. We will be using the new IFC writer, introduced in FME 2025, to perform this.

Requirements

• FME Form 2025.2+

Source Data

The source data is an AutoCAD DWG dataset representing a building floor plan.

The floor plan polygons will be elevated to the proper floor height. They possess attributes for the room number (Name), purpose (LongName), and ceiling height (Height).

Step-by-Step Instructions

1. Add a RealDWG/DXF Reader

In a blank workspace, add a new reader to the canvas. 

• Format: Autodesk AutoCAD RealDWG/DXF 
• Dataset: \FloorPlan.dwg
• Workflow Options: Single Merged Feature Type

Then click OK.

Part 1: Create Floors

2. Sample floors

Add a Sampler transformer and connect it to the reader feature type. This will sample one feature per floor, allowing us to assign features to their corresponding floors. 

In the Sampler Parameters: 

• Group Processing: Enabled
  • Group By: fme_feature_type
• Sampling Type: First N Feature

3. Add an AttributeCreator

Add an AttributeCreator to the canvas. Connect the Sampled output port to the AttributeCreator. In the Parameters, create new attributes as follows:

Of particular interest, we are adding ifc_global_id, which will be used to assign the floor as a parent feature of each space.

4. Add an AttributeRenamer

Add an AttributeRenamer:

• Input Attribute: ifc_global_id
• Output Attribute: ifc_parent_id

Part 2: Create Spaces

6. Add an Extruder

Add an Extruder transformer to the canvas and connect the reader feature type to it. In the parameters:

• Distance: Height

7. Add an AttributeCreator

Add another AttributeCreator to the canvas, connect it to the Extruder, and set the values as shown in the table below:

8. Add a FeatureMerger

Add a FeatureMerger transformer to the canvas, connect the AttributeRenamer to the Supplier input port and connect the AttributeCreator_2 to the Requestor input port. In the Parameters:

• Join On:
  • Requestor: fme_feature_type
  • Supplier: fme_feature_type
• Merge Parameters:
  • Feature Merge Type: Attributes Only
  • Reject Null and Missing Keys: No
• Attribute Accumulation: 
  • Accumulation Mode: Merge Supplier
  • Conflict Resolution: Use Requestor
  • Ignore Nulls: Yes

9. Writing to IFC 

Add a writer to the canvas:

• Format: Industry Foundation Classes (IFC)
• Dataset: <browse to a folder location>\CAD_to_IFC_output.ifc 

The deprecated IFC (STEP/XML) format is still present in the formats list and will not work for this tutorial. Ensure the (IFC) format is selected.

In the Feature Type dialog, set:

• IFC Element Type Name: BuildingStorey

Next, duplicate the BuildingStorey feature type by right-clicking on it and selecting Duplicate.

Rename the duplicated write feature type to:

• IFC Element Type Name: Space

Finally, connect the AttributeCreator to the BuildingStorey feature type and the Merged port from the FeatureMerger to the Space feature type.

Results in IFC

Here is the result when viewed in FME Data Inspector.

Data Attribution

Data was obtained from an Autodesk Revit sample and converted using FME.