CV-2x3-122 (aka CV-06-122)
Extrusion thickness of opening elements should be within reasonable boundaries
Based on IFC2x3
Initiator ISG Meeting-Munich
Effects Extended Coordination View
Date 2006 05 05
The size of an opening element should be related to the opening created in the voided element, and not an arbitrary size of a subtraction body (as in an CSG difference operation). However in many cases, these sizes (of the opening element and the created void) cannot be identical. One example is the opening in a round wall, where the opening body (when extruded horizontally) need to be bigger than the body of the round wall.
The following agreement has been made:
*the size of the opening element should not exceed the bounding box of the voided element
*the receiving system may increase the opening extrusion depth by an acceptable epsilon value to avoid numerical problems with the faces
NOTE [added 04-11-2011]
See also CV-2x3-112 about CSG being allowed for export in IFC2x3 Coordination View V2.0. In all cases, where the opening does not represent an opening / recess as a semantic object (providing a passageway for people, good, light, air, fluids, etc.) use CSG shape representation instead.