Defined in File Ifc4x3_rc1.h
IfcGrid: public Ifc4x3_rc1::IfcPositioningElement¶
IfcGrid ia a planar design grid defined in 3D space used as an aid in locating structural and design elements. The position of the grid (ObjectPlacement) is defined by a 3D coordinate system (and thereby the design grid can be used in plan, section or in any position relative to the world coordinate system). The position can be relative to the object placement of other products or grids. The XY plane of the 3D coordinate system is used to place the grid axes, which are 2D curves (for example, line, circle, trimmed curve, polyline, or composite curve). The inherited attributes Name and Description can be used to define a descriptive name of the grid and to indicate the grid’s purpose.A grid is defined by (normally) two, or (in case of a triangular grid) three lists of grid axes. The following table shows some examples. A grid may support a rectangular layout (Figure 28), a radial layout (Figure 29), or a triangular layout (Figure 30).
Figure 28 — Grid rectangular layout Figure 29 — Grid radial layout Figure 30 — Grid triangular layout
The grid axes, defined within the design grid, are those elements to which project objects will be placed relatively using the IfcGridPlacement.
HISTORY New entity in IFC Release 1.0. Informal Proposition
Grid axes, which are referenced in different lists of axes (UAxes, VAxes, WAxes) shall not be parallel. Grid axes should be defined such as there are no two grid axes which intersect twice (see Figure 31).
left side: ambiguous intersections A1 and A2, a grid containing such grid axes is not a valid design grid. right side: the conflict can be resolved by splitting one grid axis in a way, such as no ambiguous intersections exist.
Figure 31 — Grid intersections
Geometry Use Definitions The geometric representation of IfcGrid is given by the IfcProductDefinitionShape, allowing geometric representations. Included are: Local Placement The local placement for IfcGrid 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.
The PlacementRelTo relationship of IfcLocalPlacement shall point (if given) to the local placement of the same IfcSpatialStructureElement, which is used in the ContainedInStructure inverse attribute, or to a spatial structure element at a higher level, referenced by that. If the relative placement is not used, the absolute placement is defined within the world coordinate system.
Geometric Representations Currently, the use of a 2D ‘FootPrint’ representation of type ‘GeometricCurveSet’ is supported. GeometricCurveSet representation The 2D geometric representation of IfcGrid is defined using the ‘GeometricCurveSet’ geometry. The following attribute values should be inserted
The following constraints apply to the 2D representation:
The IfcGeometricCurveSet shall be an (and the only) Item of the IfcShapeRepresentation. It should contain an IfcGeometricCurveSet containing subtypes of IfcCurve, each representing a grid axis. Applicable subtypes of IfcCurve are: IfcPolyline, IfcCircle, IfcTrimmedCurve (based on BaseCurve referencing IfcLine or IfcCircle). Each subtype of IfcCurve may have a curve style assigned, using IfcAnnotationCurveOccurrence referencing IfcCurveStyle. Optionally the grid axis labels may be added as IfcTextLiteral, and they may have text styles assigned, using IfcAnnotationTextOccurrence referencing IfcTextStyle.
As shown in Figure 32, the IfcGrid defines a placement coordinate system using the ObjectPlacement. The XY plane of the coordinate system is used to place the 2D grid axes. The Representation of IfcGrid is defined using IfcProductRepresentation, referencing an IfcShapeRepresentation, that includesIfcGeometricCurveSet as Items. All grid axes are added as IfcPolyline to the IfcGeometricCurveSet.
Figure 32 — Grid layout
As shown in Figure 33, the attributes UAxes and VAxes define lists of IfcGridAxis within the context of thegrid. Each instance of IfcGridAxis refers to the same instance of IfcCurve (here the subtype IfcPolyline) that is contained within the IfcGeometricCurveSet that represents the IfcGrid.
Figure 33 — Grid representation
List of grid axes defining the first row of grid lines.
List of grid axes defining the second row of grid lines.
List of grid axes defining the third row of grid lines. It may be given in the case of a triangular grid.
Whether the optional attribute PredefinedType is defined for this IfcGrid.
IfcGrid(std::string v1_GlobalId, ::Ifc4x3_rc1::IfcOwnerHistory *v2_OwnerHistory, boost::optional<std::string> v3_Name, boost::optional<std::string> v4_Description, boost::optional<std::string> v5_ObjectType, ::Ifc4x3_rc1::IfcObjectPlacement *v6_ObjectPlacement, ::Ifc4x3_rc1::IfcProductRepresentation *v7_Representation, IfcTemplatedEntityList<::Ifc4x3_rc1::IfcGridAxis>::ptr v8_UAxes, IfcTemplatedEntityList<::Ifc4x3_rc1::IfcGridAxis>::ptr v9_VAxes, boost::optional<IfcTemplatedEntityList<::Ifc4x3_rc1::IfcGridAxis>::ptr> v10_WAxes, boost::optional<::Ifc4x3_rc1::IfcGridTypeEnum::Value> v11_PredefinedType)¶