This tool is in beta. Check the resulting model carefully before you use it in production work.
The Downgrade IFC tool downgrades the current model to an older IFC version. It can downgrade an IFC4.3 or IFC4 model to IFC2x3, and an IFC4.3 model to IFC4.
Use the tool when the application that will use the model does not support the IFC version of the model. When you export the downgraded model with the Export IFC tool, the file is written in the older IFC version.
An older IFC version cannot express everything that a newer one can. The tool replaces such content with the closest match in the older version, and keeps the name of the original class in the object, so that the Upgrade IFC tool can bring the original class back later. Some information is lost, see What is not carried over below.
If you only need the IFC versions to match when merging models, you can use the Match IFC version setting of the Merge Model tool. It does the same conversion for the merged models, and converts them to the IFC version of the current model.
The tool changes the current model directly. The operation cannot be undone.
An IFC4.3 model that contains alignments cannot be downgraded. IFC4 and IFC2x3 cannot represent alignments. The tool reports an error with the number of alignment objects, and the model is not changed.
What the downgrade changes
The downgrade changes the data structures of the model to match the older IFC version. Objects in classes that the older version does not have move to a class that it does have. They keep their geometry, properties, quantities, group memberships and colors, and the relationships between the objects are updated, so that, for example, an Earthworks Cut that became a Voiding Feature is still connected to the object it cuts.
The properties and quantities stay in their own property sets, so a Building Element Proxy that was a Course can have the properties of Pset_CourseCommon. An excluded property stays excluded. The report lists the property columns that were added to the new object classes.
When downgrading from IFC4.3 to IFC4, the object classes change as follows. Type objects change in a similar way.
| Object class in IFC4.3 | Object class in IFC4 |
|---|---|
| Bearing, Built Element, Course, Deep Foundation, Earthworks Element, Earthworks Fill, Kerb, Mooring Device, Navigation Element, Pavement, Rail, Reinforced Soil, Track Element, Vehicle | Building Element Proxy |
| Bridge, Facility, Marine Facility, Railway, Road | Building |
| Bridge Part, Facility Part, Marine Part, Railway Part, Road Part | Building Storey |
| Borehole, Geomodel, Geoslice, Geotechnical Stratum | Geographic Element |
| Impact Protection Device, Sign, Tendon Conduit, Vibration Damper | Discrete Accessory |
| Caisson Foundation | Pile |
| Earthworks Cut | Voiding Feature |
| Conveyor Segment | Flow Segment |
| Liquid Terminal, Signal | Flow Terminal |
| Electric Flow Treatment Device | Flow Treatment Device |
| Mobile Telecommunications Appliance | Communications Appliance |
| Distribution Board | Electric Distribution Board |
| Built System | Building System |
When downgrading from IFC4 to IFC2x3, the object classes change as follows.
| Object class in IFC4 | Object class in IFC2x3 |
|---|---|
| Air Terminal, Audio Visual Appliance, Communications Appliance, Electric Appliance, Fire Suppression Terminal, Lamp, Light Fixture, Medical Device, Outlet, Sanitary Terminal, Space Heater, Stack Terminal, Waste Terminal | Flow Terminal |
| Air Terminal Box, Damper, Electric Time Control, Flow Meter, Protective Device, Switching Device, Valve | Flow Controller |
| Cable Carrier Fitting, Cable Fitting, Duct Fitting, Junction Box, Pipe Fitting | Flow Fitting |
| Cable Carrier Segment, Cable Segment, Duct Segment, Pipe Segment | Flow Segment |
| Duct Silencer, Filter, Interceptor | Flow Treatment Device |
| Compressor, Fan, Pump | Flow Moving Device |
| Electric Flow Storage Device, Tank | Flow Storage Device |
| Air To Air Heat Recovery, Boiler, Burner, Chiller, Coil, Condenser, Cooled Beam, Cooling Tower, Electric Generator, Electric Motor, Engine, Evaporative Cooler, Evaporator, Heat Exchanger, Humidifier, Motor Connection, Solar Device, Transformer, Tube Bundle, Unitary Equipment | Energy Conversion Device |
| Actuator, Alarm, Controller, Flow Instrument, Protective Device Tripping Unit, Sensor, Unitary Control Element | Distribution Control Element |
| Furniture, System Furniture Element | Furnishing Element |
| Chimney, Civil Element, Geographic Element, Shading Device, Surface Feature | Building Element Proxy |
| Vibration Isolator | Discrete Accessory |
| Voiding Feature | Opening Element |
| Building System, Distribution System | System |
| Door Type, Window Type | Door Style, Window Style |
| Distribution Circuit | Electrical Circuit |
| Electric Distribution Board | Electric Distribution Point |
| Burner Type | Gas Terminal Type |
| Structural Curve Action | Structural Linear Action |
| Structural Surface Action | Structural Planar Action |
| Standard case and elemented case classes, for example Beam Standard Case | The parent class, for example Beam |
An IFC4.3 model that is downgraded to IFC2x3 goes through both of these steps.
What is not carried over
Check what the tool reports after the downgrade. Values that the older version cannot hold are listed as values not supported by the target IFC version.
- The Predefined Type of a replaced object usually does not stay. It becomes USERDEFINED or is left out, depending on the new object class.
- A Predefined Type value that the older version does not have becomes USERDEFINED, and the value is written to the Object Type if that is empty (for type objects, to the Element Type). In IFC2x3 many classes, such as Wall and Beam, have no Predefined Type at all, and the value is written to the Object Type in the same way.
- In IFC2x3, material profile sets and material constituent sets become material lists. The list stays associated with the objects, but the names of the profiles and constituents, the fractions, the categories and the profile definitions are lost.
- Geometry that the older version cannot express, such as triangulated face sets in IFC2x3, is exported as BREP geometry made from the triangles that Simplebim shows in 3D. The tool gives a warning if some of this geometry cannot be exported.
- Some geometry is simplified in IFC2x3. Tapered solids lose the taper, and the curved segments of indexed poly curves become short straight segments.
- Content that has no replacement in the older version stays in the model but it is not exported. The report tells how many of these objects are left in each class. For example, map conversions, which hold georeferencing information, are not written to an IFC2x3 file.
How the original class is kept
The name of the original class is written to the Object Type of the replaced object (for type objects, to the Element Type). For example, a Course becomes a Building Element Proxy with the Object Type Course and the Predefined Type USERDEFINED, and an Earthworks Fill gets the Object Type EarthworksFill.
If the object already had its own Object Type, the text is kept in the 01_Original object type property in the Simplebim property set. In the exported IFC file the name of the property is 01_OriginalObjectType.
This information is also written to the exported IFC file. When you later use the Upgrade IFC tool on the downgraded model, or on a model imported from that file, the original classes and Object Types are restored, and the properties and quantities move back with the objects.
When there is nothing to downgrade
If the model already has the selected IFC version or an older one, the tool does not change the model. The tool never raises the IFC version of a model; use the Upgrade IFC tool for that.
This situation is reported as information and not as an error, so you can keep the tool in a dataflow that processes models of different IFC versions.
If the model has no IFC version or no IFC data, the tool reports an error and does not change the model.
Settings
Downgrade To
Defines the IFC version to which the model is downgraded.
IFC2x3
Downgrade an IFC4.3 or IFC4 model to IFC2x3. This is the default.
IFC4
Downgrade an IFC4.3 model to IFC4.
Release Notes
This tool was added in Simplebim 12.0 SR1
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