IFC-based clash detection for the open-source BIMserver

When designing construction objects, different disciplines have to collaborate intensively. Each discipline is responsible for its own contribution to the overall design. However, when the partial designs are combined, objects from different disciplines might occupy the same position in space or 'clash'. Such a clash will often be noticed during the construction process requiring a lot of extra time and cost. Using 3D visualization, it is possible to combine the partial designs of all partners and find the clashing objects visually in an early stage. However, when the complexity of a construction project increases, a clash easily stays unnoticed. Besides, much more time is needed for inspecting a complex design. Therefore, an algorithm to discover clashes will be more reliable and efficient. Clash detection techniques are already available in 3D graphics (referred to as 'collision detection'). There are a great number of methods described on the internet on how to perform this collision detection. All these methods are based on describing objects in terms of 3D shapes, but do not take into account the structure/hierarchy of objects that is common in construction projects. In the AEC industry, the Industry Foundation Classes (IFC) open standard holds this structure next to the 3D shape of building objects. By using the IFC standard to perform clash detection on construction models, the structure of objects can be utilized, resulting in a much higher performance. This paper will demonstrate how to combine the best collision detection methods with the structure provided by IFC, making clash detection fast enough to be used inside a real time environment like a server. This clash detection is currently implemented in the IFC Engine viewer developed by TNO, and works on models opened from their open-source BIMserver (Building Information Model) where the collaboration starts. The next step would be integrating the clash detection inside the server.