- What is IFC and MVD?
- Who supports IFC?
- What information does an IFC model carry?
- What does “Reference Concept” mean?
- What functions does ArchiCAD support with IFC?
- Which methods can I use to import an IFC file into ArchiCAD?
- What does “detect IFC model version changes” function mean?
- What IFC versions does ArchiCAD support?
- What are the differences between the different IFC 2×3 formats?
- Does Hotlink work with IFC files?
- How can I check the result of my IFC model export?
- Where can I read more about IFC and the suggested data exchange workflow with other disciplines?
What is IFC and MVD?
The IFC file format is ISO-certified and developed by the IAI (BuildingSMART). IFC is the only open and standard 3D object-oriented exchange format used by BIM (Building Information Modeling). IFC is available free to all software vendors.
IFC provides 3D geometry representation for all project elements and stores standard and custom data about each element, such as materials, profiles, and functions. Applications used by the different disciplines can easily and quickly filter and identify the relevant, discipline-specific information from the IFC database.
The Coordination View was the first Model View Definition (MVD) developed by buildingSMART International and is currently the most widely implemented view of the IFC scheme. The main purpose of the Coordination View is to allow sharing of building information models among the disciplines of architecture, structural engineering, and building services (mechanical). It contains definitions of spatial structure, building, and building service elements that are needed for coordinating design information among these disciplines. The IFC2x3 Coordination View is the built-in and default standard supported by ArchiCAD.
The Coordination View (Surface Geometry) is a simplified publishing format (i.e. a subset) of the Coordination View. This format is suitable for viewing (since all IFC viewers support this format), design coordination, clash prevention during design, and clash checking. “Coordination View (Surface Geometry)” means that every element will be exported with its BREP (boundary representation) geometry. This method comes closest to reproducing the real shape of the element, together with its specialized sections, connections and solid operations. (However, the element’s parameters are lost, and BREP elements from an imported IFC file are transformed into non-editable elements.)
There are several other Model View Definitions (generally the extended versions of the Coordination view) specified by organizations or development teams outside of buildingSMART International. An example is the “Concept Design BIM 2010” MVD that is supported/required by the General Services Administration (US GSA), Statsbygg (Norway) and Senate Properties (Finland). Another example is the “FM Handover” MVD, which was developed by buildingSMART to exchange facility management information among building models, and which provides input data for COBie2-required documentation. The additional MVDs require programs to provide IFC data above and beyond those of the Coordination View standard – such extra data include Classification Reference, Space Occupant, Actor and specific property sets and properties. ArchiCAD’s IFC interface provides the possibility to define, export and import these data types. As a result, users will be able to fulfill for example the GSA-specific classifications according to UniFormat and the various OmniClass classes, etc.
All Model View Definitions can be extended by add-on model view definitions which support additional exchange requirements:
- the Quantity Take-off add-on view adds the ability to transmit base quantities for all spatial and building elements
- the Space Boundary add-on view adds building elements to space relationships to support models in thermal and energy analysis
- the 2D Annotation add-on view supports the exchange of additional 2D element representations and annotations of building models
ArchiCAD supports all of these additional data types.
For more information, visit:
Who supports IFC?
With the open IFC platform, ArchiCAD can communicate with a wide range of major and local structural, mechanical and energy analysis applications.
Check the following sites or ask your consultant about the IFC compatibility of any current application:
What information does an IFC model carry?
- Building hierarchy (Project, Site, Building, Story, Element)
- Element type (wall, slab, column, beam, roof, stair, zone etc.)
- Standard and custom (application-dependent) IFC properties (material, color, cross-sections, fire rating etc.)
What does “Reference Concept” mean?
Each discipline is responsible for the creation and development its own model. “Reference model” means that a discipline – for example the structural engineer – uses the architectural model as the initial basis for the structural model. While the structural model will be created as a standalone model, some initial design information will be taken over from the architectural model.
The modeling concepts of the two disciplines differ: for example, the architect designs a two-story column as a single, continuous column element in the architectural design. The structural engineer, on the other hand, cuts two separate structural column members and defines their final structural material and cross-section.
If such differences between the models (and the varying responsibilities of the two disciplines) are to be managed effectively, it is necessary that one discipline’s model be locked for editing when viewed in another discipline’s environment, yet its elements and data should still be accessible if needed. IFC fulfills this requirement too.
As of ArchiCAD 14, ArchiCAD’s IFC user interface has been based on this Reference Model Concept, as well as ease of use. IFC model elements inserted into the architectural model serve as protected reference elements, assigned to layers with different intersection priorities, but all of the associated data can be queried and are accessible. The elements themselves can be added to the architectural model: when you import a model into ArchiCAD using IFC, the imported elements are automatically interpreted as native ArchiCAD elements (ArchiCAD Column, Beam, Slab, Wall, Stair etc.). Thus, if needed, the imported elements can be edited immediately.
What functions does ArchiCAD support with IFC?
ArchiCAD comes with numerous tools and an easy to use interface to support IFC-based collaboration among disciplines. Read the following articles to get more information about ArchiCAD’s IFC-related skills:
- ArchiCAD & IFC – Achieving 3D-based interoperability
published in the 3/2011 issue of ArchiMAG, October 2011
- Open BIM: The next chapter – new IFC developments in ArchiCAD 16
published in the 3/2012 issue of ArchiMAG, October 2012
The most important features are the followings.
- Element Classification
For more accurate model mapping, you can classify ArchiCAD elements by their “IFC type”. While each ArchiCAD element type has a default counterpart in IFC (which is used if you use the “Automatic” option), you can assign any other IFC type to a particular element – for example, if you have used certain tools to model elements of a different type, such as using the Slab tool to model a ceiling etc.
In collaborating with structural partners, the “Structural Function” classification can be added to the load-bearing building elements. It also lets you limit the exported IFC model to load-bearing elements only, thereby streamlining the collaboration process.
The “Position” classification lets you sending a model to a partner (e.g. energy analyzer) who is able to differentiate elements by their location (interior or exterior) in the building.
Classification Reference ( IfcClassificationReference ) can be used for arrangement of IFC elements into categories. You can assign an Item Reference identifier, a classification Name attribute and some other optional parameters to all project elements (such as the building, the stories, the building elements, or the zones). For example, classify building elements by the U.S. GSA standard categories such as OmniClass , UniFormat etc.
Use IFC Assignments (Groups, Zones, Actors and Space Occupants) to define the relationship between the different project elements. Each assignment type can have its own attributes and standard/custom IFC Properties.
- Handling of IFC data
Easy handling of IFC data can be done both on the element level (in Element Settings) and on the project level (in the IFC Manager), in Teamwork as well as solo projects. Since the IFC properties are native to ArchiCAD, the following functions are available:
- Find & Select command searches for the IFC properties of any element.
- Interactive Element Schedule lists the IFC properties of any element.
- Pick up/Inject Parameters shortcuts and Copy-Paste transfers IFC properties from one element to another.
- The IFC content of Hotlinked Modules can be queried and listed.
- Mapping between ArchiCAD Library Part properties and standard/custom IFC properties is available.
- Solutions for different workflows
ArchiCAD offers solutions for different workflows: reference model concept (Merge and Hotlink); open IFC as separate new project (Open); “compare and merge” of imported model versions (Detect IFC Model Changes); and filtered or entire model export (Save as).
Each solution supports all the IFC file versions: IFC, IFCXML and IFCZIP.
Predefined and customizable translators give user-friendly “one-click” IFC import/export and optimized data transfer with major (Tekla Structures, Revit applications etc.) and local engineering softwares.
- Model export
The entire current ArchiCAD project, or just its filtered content, can be exported in IFC format. Filtration can be done by selection in the current project view, by visible layers, by building stories, by domain types (structural, HVAC or custom), by element types (e.g. columns, beams etc.), etc. Use “simplified BREP” (boundary representation) geometry export to e.g. IFC viewers, resulting in accurate geometric display of element intersections and solid operations, without including all element properties.
- Model import
The IFC model obtained from another application is always transformed into native ArchiCAD elements. At the same time, it is possible to use the imported elements as a reference, since they can be automatically placed onto their own, protected layers (which are locked to prevent editing). Since the incoming elements or modifications are converted into native format, they become an active part of the architectural model, while retaining their properties (e.g. material, profile) assigned in e.g. the received structural model.
- Detect IFC model version changes
As part of an IFC model-based data exchange workflow, ArchiCAD enables you to compare two subsequent versions of an IFC model, to insert and to list the detected changes into the current ArchiCAD model (using Mark-Up tool).
Which methods can I use to import an IFC file into ArchiCAD?
- Use Merge to add the IFC model content (or part of it) to the currently running ArchiCAD project. Merged model data are converted into native ArchiCAD elements, which can then be used as a protected or editable reference. The imported content, used as a reference, is separated from the host project elements, and can be displayed together or independently from the original project data by choosing a visualization technique.
- The Open command launches an IFC model as a separate ArchiCAD file, independent of any other project currently open in ArchiCAD. This imported file (or a part of it) can be added later as a reference to the appropriate part of another ArchiCAD project as a Hotlinked Module.
What does “detect IFC model version changes” function mean?
With the so-called “Detect IFC Model Changes” function, ArchiCAD detects the geometric differences between two versions of an IFC model (it compares two IFC files that are two versions of the same project according to the elements’ IFC global unique identifiers), and finds the new, deleted and modified elements. The elements affected by the modifications are generated and merged into the currently running project (that project can also be an empty one). Modifications can be viewed and managed using ArchiCAD’s Mark-Up tool in both 2D and 3D views.
What IFC versions does ArchiCAD support?
Industry Foundation Classes (IFC) are the open and neutral data format for openBIM. ArchiCAD supports the import, export and data structure of the latest IFC release: IFC2x Edition 3 (third release of the IFC 2x Platform, IFC2x3 for short).
What are the differences between the different IFC 2×3 formats?
- .ifc: the original normal, uncompressed format.
- .ifcxml: recommended for architects whose partners’ applications cannot read the original .ifc format, but can manage .xml databases (such as budget, energy calculations, etc.). This is also an uncompressed format, with larger file sizes than the normal .ifc format.
- .ifczip: the compressed version of both the normal and the xml-type formats, resulting in file size that is, on average, one-quarter of the original (file size varies depending on model size).
You cannot directly hotlink an IFC file to ArchiCAD. However, if you hotlink a project file that contains data opened or merged from an IFC file, elements’ IFC properties will be included in the hotlink, because they are defined as part of the ArchiCAD elements.
How can I check the result of my IFC model export?
After exporting an IFC model, it is good practice to check the IFC model by reopening it in ArchiCAD or opening it in an IFC viewer. There are many free IFC viewers on the market that can be readily downloaded, for example:
- Tekla BIMsight: http://www.teklabimsight.com/
- Solibri Model Viewer: http://www.solibri.com
- DDS-CAD Viewer: http://www.dds-cad.net
- Nemetschek IFC Viewer: http://www.nemetschek.co.uk/ifc
Additional information can be found at the following Wiki address: http://www.ifcwiki.org
Where can I read more about IFC and the suggested data exchange workflow with other disciplines?
A dedicated chapter (called Interoperability) of the ArchiCAD Help gives a detailed description of the collaboration-related topics including the suggested and effective workflow between the architects and the structural/MEP/energy analysis engineers, the ArchiCAD features that can be used to prepare a model for later data exchange, as well as the IFC-related concepts, skills and all functions.