ArchiCAD & IFC – Achieving 3D-based Interoperability

Open BIM and IFC

The goal of Building Information Modelling (BIM) is to create a comprehensive building model that can be effectively applied throughout the entire lifecycle of the building (including design, construction, maintenance) by all the participants – architects, engineers, builders and owners – in the Architecture, Engineering and Construction industry (AEC). BIM contains significantly more data than traditional, two-dimensional drawings. This additional information can facilitate and speed up the design, construction and facility management processes, but only if this additional information is available freely and without restriction to all participants.

Although open BIM is not the same as IFC (Industry Foundation Classes), IFC is the only open and standard 3D object-oriented exchange format used by BIM. 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. Appli-cations used by the different disciplines can quickly filter and identify the relevant, discipline-specific information from the IFC database.

From the start, Graphisoft has recognized the significance of the IFC standard: ArchiCAD was designed to support the very earliest versions of IFC.

Currently, the most widely implemented IFC standard worldwide is the IFC 2×3 Coordination View, also supported by ArchiCAD. The Coordination View targets the coordination of architectural, mechanical and structural engineering tasks during the design phase, and contains definitions of spatial structure, building, and building service elements needed to coordinate design information among these disciplines.

Reference Model Concept

Each discipline is responsible for creating and developing 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 modelling 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 while the structural engineer 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 is 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 on maximizing 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.

ArchiCAD’s IFC Technology

ArchiCAD comes with numerous tools and an easy-to-use interface to support IFC-based collaboration among disciplines. The most important features are the following.

  • Detailed element filtering for export and import (using the Element Type Classification and Partial Structure Display controls in ArchiCAD)
  • Easy handling of IFC data (e.g. column profiles, structural materials, fire rating data) both on the element level (in Element Settings) and on the project level (in the IFC Manager), in Teamwork as well as solo projects
  • Easy transfer of IFC data to the model and among elements (with Copy/Paste and Pick Up/Inject Parameters)
  • 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.
  • Simplified BREP (boundary representation) geometry export to IFC viewers, for example, resulting in an accurate geometric display of element intersections and solid operations, without including all element properties
Accurate geometry export via IFC (checked in IFC viewers).

Accurate geometry export via IFC (checked in IFC viewers).

  • Predefined and customizable translators for user-friendly, ‘one-click’ IFC import/export and optimized data transfer with major (Tekla Structures, Revit applications etc.) and local engineering softwares
Filtered model for different IFC exports.

Filtered model for different IFC exports. Model in question is a Microsoft Office Complex in Graphisoft Park, Budapest Architect: Lukacs and Vikar Architects, Hungary,

  • Mapping between ArchiCAD Library Part properties and standard/custom IFC properties
  • Up-to-date IFC engine that supports 64-bit and data exchange (Unicode) between Windows and Mac.

Graphisoft also provides solutions to improve interdisciplinary workflow with other applications: for example, the Add-Ins developed for use with Revit applications, which ensure direct and improved IFC connections with ArchiCAD. MEP Modeler for ArchiCAD provides intelligent integration of the imported MEP systems into the architectural design and detects any collisions among elements.

Merged intelligent MEP model (in ArchiCAD’s MEP Modeler environment).

Merged intelligent MEP model (in ArchiCAD’s MEP Modeler environment).

The ArchiCAD Reference Guide devotes a separate chapter to the topic of Interoperability and the use of IFC. Other resources (videos and tutorials) are also available to show the way to effective IFC-based collaboration with other disciplines and programs.

Related websites

IFC Downloads:

This article was published in the 3/2011 issue of ArchiMAG in October 2011.

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