OpenBuildings Designer IFC Export #2: Part Mapping to IFC TYPE

by | Apr 15, 2024 | Evolve Consultancy

It is common when first exporting data from OpenBuildings Designer to IFC that the results are “less than ideal”. In our experience, when this happens, the first response is “IFC isn’t suitable” or “the client requirements are not possible to deliver” when, quite often, they are.

One example is the mapping of Families and Parts to IFC. A common misunderstanding is that it is only possible to convert to an IfcEntity, not an IfcType. But why is this important?

Take a simple example of a pipe. You would hope that this has been set up correctly using a DataGroup, but so often in the infrastructure world (where Bentley tools are more prevalent) OpenBuildings Designer is used for drawing production – old school “mini BIM”, rather than considering effective information modelling. Pipes are usually simple cylinders with a family & part applied.

However, when setting part mapping in the IFC Export options, it is only possible to select an IfcEntity, not IfcPipeSegmentType. The only option offered is IfcFlowSegment (the related IfcEntity).

If this is used, the resultant IFC is not correct. It becomes a generic IfcDistributionElementType and is indistinguishable from any other flow segment incorrectly mapped, such as a duct:

This leads most people to assume it is not possible to convert the element correctly, but this is not true. You need to know a little bit about the files in the background that are used to define these settings.

The mapping selections are written to an IFC_PartMapping.set file, a simple tab-delimited text file which can be edited directly. (Look for it in your Workspace’s standards\setting\ folder, or if your workspace isn’t set up effectively, the original delivered Dataset’s setting folder.) It is usually much quicker to edit this file directly, and can of course, be opened in Excel to make coping and pasting values easier. When editing the mapping file directly, it is possible to enter the full IFC entity, type and even pre-defined type in the format:

Family (tab) Part (tab) IfcEntity.IfcType.PREDEFINED

An example might be:

When this is used, the element converts perfectly to a pipe rather than a generic flow element:

The IFC export from OpenBuildings Designer is full of these little “additional possibilities”. Sometimes, you’ve just got to know what you should be aiming for and do a little digging!

The expectation of IFC export from OpenBuildings Designer is that it can be completely configured in the interface but, like any Bentley product, the real configuration can be done using the configuration and settings files.