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IfcPolygonalBoundedHalfSpace

Definition from IAI: The polygonal bounded half space is a special subtype of a half space solid, where the material of the half space used in Boolean expressions is bounded by a polygonal boundary. Both, the base surface of the half space and its polygonal boundary are defined in the same position coordinate system.

The boundary is defined by a 2 dimensional polyline within the XY plane of the position coordinate system. The side of the surface which is in the half space is determined by the surface normal and the agreement flag. If the agreement flag is TRUE, then the subset is the one the normal points away from. If the agreement flag is FALSE, then the subset is the one the normal points into.

NOTE A polygonal bounded half space is not a subtype of solid model (IfcSolidModel), half space solids are only useful as operands in Boolean expressions.

HISTORY New class in IFC Release 2x

Illustration:

half space solid

Purpose
The polygonal bounded half space is used to limit the volume of the half space in Boolean difference expressions. Only the part that is defined by a theoretical intersection between the half space solid and an extruded area solid, defined by extruding the polygonal boundary, is used for Boolean expressions.

Parameter
The PolygonalBoundary defines the 2D polyline which bounds the effectiveness of the half space in Boolean expressions. The BaseSurface is defined by a plane, and the normal of the plane together with the AgreementFlag defines the side of the material of the half space.

EXPRESS specification:

ENTITY IfcPolygonalBoundedHalfSpace
SUBTYPE OF ( IfcHalfSpaceSolid);
Position  :  IfcAxis2Placement3D;
PolygonalBoundary  :  IfcPolyline;
WHERE
WR31  :  PolygonalBoundary.Dim = 2;
END_ENTITY;

Attribute definitions:

Position  :  Definition of the position coordinate system for the bounding polyline and the base surface.
PolygonalBoundary  :  Two-dimensional polyline defined in the xy plane of the position coordinate system.

Formal Propositions:

WR31  :  The bounding polyline should have the dimensionality of 2.

References (1):

Name Type Referred through Express-G
IfcHalfSpaceSolid Entity
Subtype
Diagram 2

Inheritance graph

ENTITY IfcPolygonalBoundedHalfSpace;
ENTITY IfcHalfSpaceSolid;
BaseSurface  :  IfcSurface;
AgreementFlag  :  BOOLEAN;
DERIVE
Dim  :  IfcDimensionCount :=  3;
ENTITY IfcPolygonalBoundedHalfSpace;
Position  :  IfcAxis2Placement3D;
PolygonalBoundary  :  IfcPolyline;
END_ENTITY;