Opening elements are used to 'punch' openings into other building elements. Currently opening elements may be used with walls and slabs (both floor slab and roof slab).
According to the IFC model opening elements can have zero to many filler elements (e.g. doors and windows), but at the moment we use only one filler element per opening. If an opening element has no filler element it represents an empty opening.
As a result of a R1.5.1 implementers agreement the bounding box geometry of doors and windows is derived from the opening element that contains them. This agreement was made because the bounding box geometry of doors and windows is identical with the bounding box geometry of the opening element (if there is only one filler element per opening element as has been agreed)
One opening element can make an opening only to one building element. For example in the case of a corner window two opening elements have to be created, one for each wall.
Geometry
BoundingBox Extruded solid Linear Rectangular 1 No No Extruded solid Linear Circular 1 No No Extruded solid Linear Arbitrary 1 No No Extruded solid Linear Curved 1 No No Extruded solid Linear Rectangular n No No Extruded solid Linear Circular n No No Extruded solid Linear Arbitrary n No No Extruded solid Linear Curved n No No Brep
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Not slanted in the context of opening elements means, that the extrusion is perpendicular to the element that the opening element voids.
- As the basic representation opening elements should always have a bounding box. The bounding box can be used as a place holder for opening elements with complex geometry in programs that are not able to support the given geometry. This could be the case e.g. in programs that don't support round opening elements, opening elements with an arbitrary profile, multi segment opening elements or Brep representation.
- Most opening elements can be represented using a single extruded solid that
has one or more segments.
- The opening element extrusion segments may have any profile, but all segments for one opening should have the same profile type. If this is not the case Brep representation should be used. Programs that internally support only one segment for opening elements can revert to the largest segment and use that for approximating the opening. It might be challenging though to examine which segment to use if the profile is arbitrary and uses IfcCompositeCurve.
- The rectangular profile should be used only for 'vertical' openings. For e.g. diamond shaped openings the arbitrary profile with a polyline should be used instead.
- When solids are used for the opening element geometry the exchange files are more compact and it is easier to derive quantities from the opening element geometry. It is also easier to map to common opening element shapes used in programs.
- In all other cases the representation is made using Brep geometry
- Opening elements where the extrusion is not perpendicular to the element (slanted opening)
- Opening elements with a profile that can't be expressed by IfcCompositeCurve. The vocabulary of the composite curve contains the following elements: straight segment, circular arc and elliptical arc.
- Opening elements with a elliptical shape (could also be made using IfcCompositeCurve)
- The following scenarios may require different implementations in software
- Solid opening in solid element
- Solid opening in Brep element
- Brep opening in solid element
- Brep opening in Brep element
Documents
Used by views
- Arch. design >> Quantities take off
- Arch. design >> Thermal load calculations / HVAC system design
- CAD / visualization
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