The IfcCurveBoundedSurface is a parametric surface with boundaries defined by p-curves, that is, a curve which lies on the basis of a surface and is defined in the parameter space of that surface. The p-curve is a special type of a composite curve segment and shall only be used to bound a surface.
The outer boundary shall be either defined by:
NOTE Some surfaces, like IfcCylindricalSurface does not have identifiable implicit boundaries.
NOTE Definition according to ISO/CD 10303-42:1992
The curve bounded surface is a parametric surface with curved boundaries defined by one or more boundary curves. One of the boundary curves may be the outer boundary; any number of inner boundaries is permissible. The region of the curve bounded surface in the basis surface is defined to be the portion of the basis surface in the direction of N x T from any point on the boundary, where N is the surface normal and T the boundary curve tangent vector at this point. The region so defined shall be arcwise connected.
NOTE Entity adapted from curve_bounded_surface defined in ISO 10303-42.
HISTORY New entity in IFC4.
|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.
|Dim||INVALID||The space dimensionality of IfcSurface. It is always a three-dimensional geometric representation item.|
> IFC4 CHANGE Derived attribute promoted from subtypes.
|1||BasisSurface||IfcSurface||The surface to be bounded.|
|2||Boundaries||SET [1:?] OF IfcBoundaryCurve||The outer boundary of the surface.|
ENTITY IfcCurveBoundedSurface SUBTYPE OF (IfcBoundedSurface); BasisSurface : IfcSurface; Boundaries : SET [1:?] OF IfcBoundaryCurve; ImplicitOuter : IfcBoolean; END_ENTITY;