IfcCsgSolid

BACnet MVD

#### IfcCsgSolid

Natural language names

| CSG - Festkörper
| Csg Solid
| Solid Csg

##### Semantic definitions at the entity

Entity 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 tesselated representation modles, 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.

> NOTE Definition according to ISO/CD 10303-42:1992
> A solid represented as a CSG model is defined by a collection of so-called primitive solids, combined using regularized Boolean operations. The allowed operations are intersection, union, and difference. As a special case a CSG solid can also consists of a single CSG primitive.
> 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.

> NOTE Entity adapted from csg_solid is defined in ISO 10303-42.

> HISTORY New entity in IFC1.5.1

Attribute definitions

# | Attribute | Type | Cardinality | Description | B
--- | --- | --- | --- | --- | ---
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 entitiy or as a primitive (subtypes of IfcCsgPrimitive3D). | X | X

##### Inherited definitions from supertypes

Entity inheritance
Attribute inheritance

# | Attribute | Type | Cardinality | Description | B
--- | --- | --- | --- | --- | ---
IfcRepresentationItem

LayerAssignment

IfcPresentationLayerAssignment
@AssignedItems

S[0:1]

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.

X

StyledByItem

IfcStyledItem
@Item

S[0:1]

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.

X

X

IfcGeometricRepresentationItem
IfcSolidModel
| Dim :=3 | IfcDimensionCount |  | The space dimensionality of this class, it is always 3. | X | X
IfcCsgSolid
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 entitiy or as a primitive (subtypes of IfcCsgPrimitive3D). | X | X

##### Examples

- CSG primitive
- Bath CSG Solid

##### Formal representations

XML Specification
`<xs:element name="IfcCsgSolid" type="ifc:IfcCsgSolid" substitutionGroup="ifc:IfcSolidModel" nillable="true"/>
<xs:complexType name="IfcCsgSolid">
<xs:complexContent>
<xs:extension base="ifc:IfcSolidModel">
<xs:sequence>
<xs:element name="TreeRootExpression">
<xs:complexType>
<xs:group ref="ifc:IfcCsgSelect"/>
</xs:complexType>
</xs:element>
</xs:sequence>
</xs:extension>
</xs:complexContent>
</xs:complexType>
`
EXPRESS Specification
`ENTITY IfcCsgSolid
SUBTYPE OF (IfcSolidModel);
TreeRootExpression : IfcCsgSelect;
END_ENTITY;

EXPRESS-G diagram

`

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