Class TIfcGeometricRepresentationSubContext

Unit

Declaration

type TIfcGeometricRepresentationSubContext = class(TIfcRepresentationContext)

Description

Context that applies to several shape representations of a product being a sub context, sharing the WorldCoordinateSystem, CoordinateSpaceDimension, Precision and TrueNorth attributes with the parent IfcGeometricRepresentationContext.

Source: scene/load/ifc/castleifc_ifc_standard_types.inc (line 4861).

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 ContextIdentifier: TIfcLabel read FContextIdentifier write FContextIdentifier;
Published property ContextType: TIfcLabel read FContextType write FContextType;
Published property RepresentationsInContext: TIfcRepresentationList read FRepresentationsInContext;
Published property ParentContext: TIfcGeometricRepresentationContext read FParentContext write FParentContext;
Published property TargetScale: TIfcPositiveRatioMeasure read FTargetScale write FTargetScale;
Published property TargetView: TIfcGeometricProjectionEnum read FTargetView write FTargetView;
Published property UserDefinedTargetView: TIfcLabel read FUserDefinedTargetView write FUserDefinedTargetView;

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 4785).

Public destructor Destroy; override;

This item has no description.

Source: scene/load/ifc/castleifc_ifc_standard_types.inc (line 4786).

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 ContextIdentifier: TIfcLabel read FContextIdentifier write FContextIdentifier;

The optional identifier of the representation context as used within a project.

Source: scene/load/ifc/castleifc_ifc_standard_types.inc (line 4789).

Published property ContextType: TIfcLabel read FContextType write FContextType;

The description of the type of a representation context. The supported values for context type are to be specified by implementers agreements.

Source: scene/load/ifc/castleifc_ifc_standard_types.inc (line 4793).

Published property RepresentationsInContext: TIfcRepresentationList read FRepresentationsInContext;

All shape representations that are defined in the same representation context.

Source: scene/load/ifc/castleifc_ifc_standard_types.inc (line 4796).

Published property ParentContext: TIfcGeometricRepresentationContext read FParentContext write FParentContext;

Parent context from which the sub context derives its world coordinate system, precision, space coordinate dimension and true north.

Source: scene/load/ifc/castleifc_ifc_standard_types.inc (line 4870).

Published property TargetScale: TIfcPositiveRatioMeasure read FTargetScale write FTargetScale;

The target plot scale of the representation to which this representation context applies.

NOTE Scale indicates the target plot scale for the representation sub context, all annotation styles are given in plot dimensions according to this target plot scale. If multiple instances of IfcGeometricRepresentationSubContext are given having the same TargetView value, the target plot scale applies up to the next smaller scale, or up to unlimited small scale.

Source: scene/load/ifc/castleifc_ifc_standard_types.inc (line 4881).

Published property TargetView: TIfcGeometricProjectionEnum read FTargetView write FTargetView;

Target view of the representation to which this representation context applies.

Source: scene/load/ifc/castleifc_ifc_standard_types.inc (line 4884).

Published property UserDefinedTargetView: TIfcLabel read FUserDefinedTargetView write FUserDefinedTargetView;

User defined target view, this attribute value shall be given, if the TargetView attribute is set to TIfcGeometricProjectionEnum.UserDefined.

Source: scene/load/ifc/castleifc_ifc_standard_types.inc (line 4888).


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