Definition from IAI: The distribution flow element IfcFlowSegment defines the occurrence of a segment of a flow distribution system that is typically straight, contiguous and has two ports (e.g., a section of pipe or duct).
The IfcFlowSegment defines a particular occurrence of a segment inserted in the spatial context of a project. The parameters defining the type of the segment and/or its shape are defined by the IfcFlowSegmentType, which is related by the inverse relationship IsDefinedBy pointing to IfcRelDefinesByType.
The following parameters shall be given:
- Segment length, taken from the Length attribute in the property set, provides the depth of the extrusion.
- Segment profile dimensions are defined by the NominalDiameterOrWidth and NominalHeight attributes in the property set.
HISTORY: New entity in IFC R2.0.
Geometry Use Definitions
The geometric representation of IfcFlowSegment is given by the IfcProductDefinitionShape, allowing multiple geometric representations. If an IfcRepresentationMap is defined for the IfcFlowSegmentType, then the IfcFlowSegment utilizes it through the IfcMappedItem.
Local Placement
The local placement is defined in its supertype IfcProduct. It is defined by the IfcLocalPlacement, which defines the local coordinate system that is referenced by all geometric representations. If specified, the PlacementRelTo relationship of IfcLocalPlacement shall point to the local placement of the referenced IfcProduct. If the relative placement is not used, the absolute placement is defined within the world coordinate system.
Informal propositions for local placement:
- If the LocalPlacement is specified, then all aggregated components should use this placement as their relative placement.
Geometric Representation
The standard geometric representation of IfcFlowSegment is defined using the following multiple shape representations for its definition:
- Axis: A two-dimensional open curve (IfcBoundedCurve) defining the axis for the segment.
- Body: A Swept Solid Representation or a CSG representation defining the 3D shape of the segment.
First representation: Axis
The segment axis is represented by a two-dimensional open curve within a particular shape representation. The segment axis is used to apply the segment length parameter to the segment geometry. The following attribute values shall be used
IfcShapeRepresentation
- RepresentationIdentifier : 'Axis'
- RepresentationType : 'GeometricSet'
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In case of a straight segment, the set of items shall include a single geometric representation item of type IfcPolyline. |
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In the case of a curved segment, the set of items shall include a single geometric representation item of type IfcTrimmedCurve. The curve shall have a BasisCurve of type IfcCircle. |
Body Representation
The body of the IfcFlowSegment is defined using:
- SweptSolid representation for segments without clippings.
- CSG representation for segments with clippings.
IfcShapeRepresentation
- RepresentationIdentifier : 'Body'
- RepresentationType : 'SweptSolid', 'CSG' 'Brep', or 'BoundingBox'
SweptSolid representation
The standard geometric representation (for body) of IfcFlowSegment is defined using the swept solid representation. The following additional constraints apply to the swept solid representation:
- Solid: IfcExtrudedAreaSolid is required,
- Profile: IfcArbitraryProfileDef shall be supported.
- Extrusion: The profile shall be extruded along the segment axis, i.e., in the direction of the x-axis of the coordinate system of local placement. The extrusion axis shall be perpendicular to the swept profile, i.e. pointing into the direction of the x-axis of the Position of the IfcExtrudedAreaSolid.
| The profile of a segment is described in plane perpendicular to the extrusion axis. The profile is defined by the IfcArbitraryProfileDef (excluding its subtypes). The profile is given with all segment connections already resolved and is always perpendicular to the segment axis. The segment also has a single, unchanged profile. |
The advanced geometric representation (for body) of IfcFlowSegment is defined using the CSG representation. The following additional constraints apply to the swept solid representation:
- Solid: see standard geometric representation
- Profile: see standard geometric representation
- Extrusion: see standard geometric representation
- Boolean result: The IfcBooleanClippingResult shall be supported, allowing for Boolean differences between the swept solid (here IfcExtrudedAreaSolid) and one or several IfcHalfSpaceSolid.
Bounding-Box Representation
IfcShapeRepresentation
- RepresentationIdentifier : 'BoundingBox'
- RepresentationType : 'BoundingBox'
Any IfcFlowSegment may be represented as a bounding box, which shows the maximum extents of the body within the coordinated system established by the IfcLocalPlacement. The bounding box representation is the simpliest geometric representation available. It is ensured by assigning the value 'BoundingBox' to the RepresentationType attribute of IfcShapeRepresentation.
B-Rep Representation
IfcShapeRepresentation
- RepresentationIdentifier : 'Brep'
- RepresentationType : 'Brep'
The faceted B-Rep capabilities (with or without voids) shall be supported for B-Rep representation.