Understanding placements in IFC using IfcOpenShell and FreeCAD

A geometry generally has its own Local Coordinate System (LCS). Why ? Take for example an air terminal. You often use a few types of air terminal in a project. The same air terminal geometry is replicated multiple time in each space. If your geometry is defined with World Coordinate System (WCS) you need to define a new geometry for each one. If your geometry is defined in its own LCS you can use same geometry everywhere and give its placement relative to another reference.

In ifc schema, an air terminal is a IfcAirTerminal (IFC4) or an IfcFlowTerminal (IFC2x3). Both are inherited from IfcProduct (as walls, windows, ducts, pipes etc…) which has an ObjectPlacement attribute of type IfcObjectPlacement.

IfcOpenShell – Placement

About thomas

Thomas Krijnen is the main author and contributor to IfcOpenShell, a software library for working with IFC files. Thomas works hard on obtaining his PhD degree at the University of Technology in Eindhoven, the Netherlands.

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