An IfcShellBasedSurfaceModel represents the shape by a set of open or closed shells. The connected faces within the shell have a dimensionality 2 and are placed in a coordinate space of dimensionality 3.
NOTE Definition according to ISO/CD 10303-42:1992
A shell based surface model is described by a set of open or closed shells of dimensionality 2. The shells shall not intersect except at edges and vertices. In particular, distinct faces may not intersect. A complete face of one shell may be shared with another shell. Coincident portions of shells shall both reference the same faces, edges and vertices defining the coincident region. There shall be at least one shell. A shell may exist independently of a surface model.
NOTE Entity adapted from shell_based_surface_model defined in ISO 10303-42.
HISTORY New entity in IFC2x.
|LayerAssignment||SET [0:1] OF IfcPresentationLayerAssignment FOR AssignedItems||Assignment of the representation item to a single or multiple layer(s). The LayerAssignments can override a LayerAssignments of the IfcRepresentation it is used within the list of Items.|
> IFC2x3 CHANGE The inverse attribute LayerAssignments has been added.
> IFC4 CHANGE The inverse attribute LayerAssignment has been restricted to max 1. Upward compatibility for file based exchange is guaranteed.
|StyledByItem||SET [0:1] OF IfcStyledItem FOR Item||Reference to the IfcStyledItem that provides presentation information to the representation, e.g. a curve style, including colour and thickness to a geometric curve.|
> IFC2x3 CHANGE The inverse attribute StyledByItem has been added.
|1||SbsmBoundary||SET [1:?] OF IfcShell|
|Dim||INVALID||The space dimensionality of this class, it is always 3.|
ENTITY IfcShellBasedSurfaceModel SUBTYPE OF (IfcGeometricRepresentationItem); SbsmBoundary : SET [1:?] OF IfcShell; DERIVE Dim : IfcDimensionCount := 3; END_ENTITY;