Traitement de surface

A surface feature is a modification at (onto, or into) of the surface of an element. Parts of the surface of the entire surface may be affected. The volume and mass of the element may be increased, remain unchanged, or be decreased by the surface feature, depending on manufacturing technology. However, any increase or decrease of volume is small compared to the total volume of the element.

The standard use of instances of IfcSurfaceFeature is as a part of element type objects (instances of subtypes of IfcElementType). The part–whole relationship is established by an aggregation relationship object, expressing the decomposition of an element type into one or more additive elements (element parts) and zero or more feature elements.

HISTORY  New entity in IFC4.

Containment Use Definition:

Surface features shall have no spatial containment relationship to the spatial structure since they are dependent on element types without spatial containment relationships or on an element occurrence with own spatial containment relationship.

Geometry use definition:

The geometric representation of IfcSurfaceFeatureElement is given by the IfcProductDefinitionShape, allowing multiple geometric representation.

Local Placement

The local placement for IfcSurfaceFeatureElement is defined in its supertype IfcProduct. It is defined by the IfcLocalPlacement, which defines the local coordinate system that is referenced by all geometric representations.

Shape representation

Different shape representations may be used, depending on the nature of the feature and information requirements:

Higher-level parameters (geometric and non-geometric) may be provided by property sets based on local agreements.

Common Use Definitions

The following concepts are inherited at supertypes:

 Instance diagram

Property Sets for Objects

The Property Sets for Objects concept applies to this entity as shown in Table 664.

Table 664 — IfcSurfaceFeature Property Sets for Objects

Product Placement

The Product Placement concept applies to this entity as shown in Table 665.
IfcLocalPlacementIfcLocalPlacementRelative placement according to position and rotation relative to container.
IfcLocalPlacement Absolute placement according to position and rotation of world coordinate system.
IfcGridPlacement Placement according to grid intersection.

Table 665 — IfcSurfaceFeature Product Placement

The local placement for IfcSurfaceFeatureElement is defined in its supertype IfcProduct. It is defined by the IfcLocalPlacement, which defines the local coordinate system that is referenced by all geometric representations.

Body Geometry

The Body Geometry concept applies to this entity as shown in Table 666.
   Surface representations of treated parts of the lement surface by means of IfcShellBasedSurfaceModel. The faces within the surface model may be included into a B-Rep model within a representation map of the parent element type.

Table 666 — IfcSurfaceFeature Body Geometry

XSD Specification:

 <xs:element name="IfcSurfaceFeature" type="ifc:IfcSurfaceFeature" substitutionGroup="ifc:IfcFeatureElement" nillable="true"/>
 <xs:complexType name="IfcSurfaceFeature">
   <xs:extension base="ifc:IfcFeatureElement">
    <xs:attribute name="PredefinedType" type="ifc:IfcSurfaceFeatureTypeEnum" use="optional"/>

EXPRESS Specification:

ENTITY IfcSurfaceFeature
SUBTYPE OF IfcFeatureElement;
PredefinedType : OPTIONAL IfcSurfaceFeatureTypeEnum;
HasObjectType : NOT EXISTS(PredefinedType) OR (PredefinedType <> IfcSurfaceFeatureTypeEnum.USERDEFINED) OR EXISTS(SELF\IfcObject.ObjectType);

Link to EXPRESS-G diagram EXPRESS-G diagram

Attribute Definitions:

PredefinedType : Indicates the kind of surface feature.

Formal Propositions:

HasObjectType : The attribute ObjectType shall be given if the predefined type is set to USERDEFINED.

Inheritance Graph:

ENTITY IfcSurfaceFeature
GlobalId : IfcGloballyUniqueId;
OwnerHistory : OPTIONAL IfcOwnerHistory;
Name : OPTIONAL IfcLabel;
Description : OPTIONAL IfcText;
ENTITY IfcObjectDefinition
HasAssignments : SET OF IfcRelAssigns FOR RelatedObjects;
Nests : SET [0:1] OF IfcRelNests FOR RelatedObjects;
IsNestedBy : SET OF IfcRelNests FOR RelatingObject;
HasContext : SET [0:1] OF IfcRelDeclares FOR RelatedDefinitions;
IsDecomposedBy : SET OF IfcRelAggregates FOR RelatingObject;
Decomposes : SET [0:1] OF IfcRelAggregates FOR RelatedObjects;
HasAssociations : SET OF IfcRelAssociates FOR RelatedObjects;
ENTITY IfcObject
ObjectType : OPTIONAL IfcLabel;
IsDeclaredBy : SET [0:1] OF IfcRelDefinesByObject FOR RelatedObjects;
Declares : SET OF IfcRelDefinesByObject FOR RelatingObject;
IsTypedBy : SET [0:1] OF IfcRelDefinesByType FOR RelatedObjects;
IsDefinedBy : SET OF IfcRelDefinesByProperties FOR RelatedObjects;
ENTITY IfcProduct
ObjectPlacement : OPTIONAL IfcObjectPlacement;
Representation : OPTIONAL IfcProductRepresentation;
ReferencedBy : SET OF IfcRelAssignsToProduct FOR RelatingProduct;
ENTITY IfcElement
Tag : OPTIONAL IfcIdentifier;
FillsVoids : SET [0:1] OF IfcRelFillsElement FOR RelatedBuildingElement;
ConnectedTo : SET OF IfcRelConnectsElements FOR RelatingElement;
IsInterferedByElements : SET OF IfcRelInterferesElements FOR RelatedElement;
InterferesElements : SET OF IfcRelInterferesElements FOR RelatingElement;
HasProjections : SET OF IfcRelProjectsElement FOR RelatingElement;
ReferencedInStructures : SET OF IfcRelReferencedInSpatialStructure FOR RelatedElements;
HasOpenings : SET OF IfcRelVoidsElement FOR RelatingBuildingElement;
IsConnectionRealization : SET OF IfcRelConnectsWithRealizingElements FOR RealizingElements;
ProvidesBoundaries : SET OF IfcRelSpaceBoundary FOR RelatedBuildingElement;
ConnectedFrom : SET OF IfcRelConnectsElements FOR RelatedElement;
ContainedInStructure : SET [0:1] OF IfcRelContainedInSpatialStructure FOR RelatedElements;
ENTITY IfcFeatureElement
ENTITY IfcSurfaceFeature
PredefinedType : OPTIONAL IfcSurfaceFeatureTypeEnum;

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