Class TIfcDirection

Unit

Declaration

type TIfcDirection = class(TIfcPersistent)

Description

Direction in 2D or 3D.

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

Source: scene/load/ifc/castleifc_ifc_standard_types.inc (line 417).

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;
Public constructor CreateVector(const AOwner: TComponent; const AVector: TVector3);

Properties

Published property GlobalId: String read FGlobalId write FGlobalId;
Published property DirectionRatios: TCastleVector3PersistentSimple read FDirectionRatios;

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;

FDim: TIfcDimensionCount;

Source: scene/load/ifc/castleifc_ifc_standard_types.inc (line 426).

Public destructor Destroy; override;

This item has no description.

Source: scene/load/ifc/castleifc_ifc_standard_types.inc (line 427).

Public constructor CreateVector(const AOwner: TComponent; const AVector: TVector3);

Create instance with given direction ratios.

Source: scene/load/ifc/castleifc_ifc_standard_types.inc (line 430).

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 DirectionRatios: TCastleVector3PersistentSimple read FDirectionRatios;

Defined as 2 or 3 values of TIfcReal type. In practice, this is just a 3D vector for our engine.

Source: scene/load/ifc/castleifc_ifc_standard_types.inc (line 440).


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