IfcShellBasedSurfaceModel

Definition from 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 Corresponding STEP entity: shell_based_surface_model. Please refer to ISO/IS 10303-42:1994, p. 187 for the final definition of the formal standard.

> HISTORY: New entity in IFC Release 2x.

Informal propositions

1. The dimensionality of the shell based surface model is 2.
2. The shells shall not overlap or intersect except at common faces, edges or vertices.

EXPRESS specification:

ENTITY IfcShellBasedSurfaceModel
SUBTYPE OF ( | IfcGeometricRepresentationItem);
SbsmBoundary | : | SET [1:?] OF IfcShell;
DERIVE
Dim | : | IfcDimensionCount := 3;
END_ENTITY;

Attribute definitions:

Dim | : | The space dimensionality of this class, it is always 3.

Inheritance graph

ENTITY IfcShellBasedSurfaceModel;
ENTITY IfcRepresentationItem;
INVERSE
LayerAssignments | : | SET OF IfcPresentationLayerAssignment FOR AssignedItems;
StyledByItem | : | SET [0:1] OF IfcStyledItem FOR Item;
ENTITY IfcGeometricRepresentationItem;
ENTITY IfcShellBasedSurfaceModel;
SbsmBoundary | : | SET [1:?] OF IfcShell;
DERIVE
Dim | : | IfcDimensionCount := 3;
END_ENTITY;