8.8.3.12 IfcCsgSolid

8.8.3.12.1 Semantic definition

An IfcCsgSolid is the representation of a 3D shape using constructive solid geometry model. It is represented by a single 3D CSG primitive, or as a result of a Boolean operation. The operants of a Boolean operation can be Boolean operations themselves forming a CSG tree. The following volumes can be parts of the CSG tree:

Boundary representation models, such as IfcFacetedBrep, IfcFacetedBrepWithVoids,
Closed tessellated representation models, such as IfcPolygonalFaceSet, IfcTriangulatedFaceSet,
Swept area solids, such as IfcExtrudedAreaSolid, IfcRevolvedAreaSolid, and their subtypes for tapering,
Advanced swept area solids, such as IfcSurfaceCurveSweptAreaSolid), IfcFixedReferenceSweptAreaSolid, IfcSweptDiskSolid
Half space solids, such as IfcHalfSpaceSolid and its subtypes), and
CSG primitives, the subtypes of IfcCsgPrimitive3D.

A CSG solid requires two kinds of information for its complete definition: geometric and structural. > * The geometric information is conveyed by solid models. These typically primitive volumes such as cylinders, wedges and extrusions, but can include general B-Rep models. Solid models can also be half space solids. * The structural information is in a tree (strictly an acyclic directed graph) of Boolean result and CSG solids, which represent a ‘recipe’ for building the solid. The terminal nodes are the geometric primitives and other solids. Every CSG solid has precisely one Boolean result associated with it which is the root of the tree that defines the solid. (There may be further Boolean results within the tree as operands). The significance of a CSG solid entity is that the solid defined by the associated tree is thus identified as a significant object itself, and in this way it is distinguished from other Boolean result entities representing intermediate results during the construction process.

8.8.3.12.2 Entity inheritance

8.8.3.12.3 Attributes

#	Attribute	Type	Description
IfcRepresentationItem (2)
	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.
IfcSolidModel (1)
*	Dim	IfcDimensionCount	This attribute is formally derived. `3` The space dimensionality of this class, it is always 3.
Click to show 3 hidden inherited attributes
IfcCsgSolid (1)
1	TreeRootExpression	IfcCsgSelect	Boolean expression of primitives and regularized operators describing the solid. The root of the tree of Boolean expressions is given explicitly as an IfcBooleanResult entity or as a primitive (subtypes of IfcCsgPrimitive3D).

Table 8.8.3.12.C

8.8.3.12.4 Examples

Figure 8.8.3.12.A

Csg Primitive
Figure 8.8.3.12.B

Bath Csg Solid

8.8.3.12.5 Formal representation

 ENTITY IfcCsgSolid
 SUBTYPE OF (IfcSolidModel);
	TreeRootExpression : IfcCsgSelect;
END_ENTITY;

8.8.3.12.6 References

IfcSolidModel

	ENTITY IfcCsgSolid
	SUBTYPE OF (IfcSolidModel);
	TreeRootExpression : IfcCsgSelect;
	END_ENTITY;