Class TIfcMaterialDefinition

Unit

Declaration

type TIfcMaterialDefinition = class abstract(TIfcMaterialSelect)

Description

General supertype for all material related information items in IFC that have common material related properties that may include association of material with some shape parameters or assignments to identified parts of a component.

Spec: https://standards.buildingsmart.org/IFC/RELEASE/IFC4_3/HTML/lexical/IfcMaterialDefinition.htm

Source: scene/load/ifc/castleifc_ifc_standard_types.inc (line 5445).

Hierarchy

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Overview

Methods

Protected function WantsGlobalId: Boolean; virtual;
Protected class function IfcClassName: String; virtual;
Public constructor Create(AOwner: TComponent); override;
Public destructor Destroy; override;

Properties

Published property GlobalId: String read FGlobalId write FGlobalId;
Published property AssociatedTo: TIfcRelAssociatesMaterialList read FAssociatedTo;
Published property HasExternalReferences: TIfcExternalReferenceRelationshipList read FHasExternalReferences;
Published property HasProperties: TIfcMaterialPropertiesList read FHasProperties;

Description

Methods

Protected function WantsGlobalId: Boolean; virtual;

If True, instances of this class will have GlobalId auto-assigned at saving, and they will be saved as part of the "data" list in IFC JSON files.

Strictly following the spec, this should be only defined for TIfcRoot, because only IfcRoot has GlobalId. In reality, we need GlobalId at TIfcPersistent to load some files, and we sometimes need WantsGlobalId = True to save some files.

Source: scene/load/ifc/castleifc_ifc_types.inc (line 52).

Protected class function IfcClassName: String; virtual;

Name for the IFC standard, used in IFC files. By default, this is just ClassName with prefix 'T' removed.

Source: scene/load/ifc/castleifc_ifc_types.inc (line 56).

Public constructor Create(AOwner: TComponent); override;

This item has no description.

Source: scene/load/ifc/castleifc_ifc_standard_types.inc (line 5451).

Public destructor Destroy; override;

This item has no description.

Source: scene/load/ifc/castleifc_ifc_standard_types.inc (line 5452).

Properties

Published property GlobalId: String read FGlobalId write FGlobalId;

Globally unique identifier for the object instance.

Note: Not declared as TGUID, because TGUID cannot be published, but also we don't really need it: for our purposes, this identifier is just an arbitrary string.

Note: IFC 4.3 specification puts this only at IfcRoot, not at every IFC class. But testcase https://github.com/buildingsmart-community/Community-Sample-Test-Files/blob/main/IFC%204.0.2.1%20(IFC%204)/ISO%20Spec%20archive/wall-with-opening-and-window.json (from IFC 4.0) shows this can be present at any IFC class, in particular TIfcGeometricRepresentationContext.

In fact, TIfcGeometricRepresentationContext needs to have GlobalId to be successfully saved (avoid recursively trying to serialize it) in some cases. We indicate such classes with WantsGlobalId.

IFC JSON documentation says this, which seems to (unfortunately it is not unambiguous enough...) allow this at any IFC class: "Whereas the globalId attribute is only available to those elements that are descendent of the IfcRoot entity in the EXPRESS schema, we encourage a broader use of this globalId, to enable referencing between objects in a JSON file when useful.".

Source: scene/load/ifc/castleifc_ifc_types.inc (line 79).

Published property AssociatedTo: TIfcRelAssociatesMaterialList read FAssociatedTo;

Use of the IfcMaterialDefinition subtypes within the material association of an element occurrence or element type.

Source: scene/load/ifc/castleifc_ifc_standard_types.inc (line 5456).

Published property HasExternalReferences: TIfcExternalReferenceRelationshipList read FHasExternalReferences;

Reference to external references, e.g. library, classification, or document information, that are associated to the material.

Source: scene/load/ifc/castleifc_ifc_standard_types.inc (line 5460).

Published property HasProperties: TIfcMaterialPropertiesList read FHasProperties;

Material properties assigned to instances of subtypes of IfcMaterialDefinition.

Source: scene/load/ifc/castleifc_ifc_standard_types.inc (line 5463).


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