IFC 4.3.2.20250327 (IFC4X3_ADD2) under development

5.4.3.35 IfcGrid

5.4.3.35.1 Semantic definition

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, arc, polyline).

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 figures show some examples.

A grid may support a rectangular layout as shown in Figure 5.4.3.35.A, a radial layout as shown in Figure 5.4.3.35.B, or a triangular layout as shown in Figure 5.4.3.35.C.

Grid rectangular layout
Figure 5.4.3.35.A — Grid rectangular layout
Grid radial layout
Figure 5.4.3.35.B — Grid radial layout
Grid triangular layout
Figure 5.4.3.35.C — Grid triangular layout

Informal Propositions

  1. Grid axes, which are referenced in different lists of axes (UAxes, VAxes, WAxes) shall not be parallel.
  2. Grid axes should be defined such that there are no two grid axes which intersect twice (see Figure 5.4.3.35.D).
Grid intersections
Figure 5.4.3.35.D — Grid intersections

5.4.3.35.2 Entity inheritance

5.4.3.35.3 Attributes

# Attribute Type Description
IfcRoot (4)
IfcObjectDefinition (7)
IfcObject (5)
IfcProduct (5)
IfcPositioningElement (2)
Click to show 23 hidden inherited attributes
IfcGrid (4)
8 UAxes LIST [1:?] OF UNIQUE IfcGridAxis

List of grid axes defining the first row of grid lines.

9 VAxes LIST [1:?] OF UNIQUE IfcGridAxis

List of grid axes defining the second row of grid lines.

10 WAxes OPTIONAL LIST [1:?] OF UNIQUE IfcGridAxis

List of grid axes defining the third row of grid lines. It may be given in the case of a triangular grid.

11 PredefinedType OPTIONAL IfcGridTypeEnum

Predefined types to define the particular type of the grid.

Table 5.4.3.35.H

5.4.3.35.4 Property sets

  • Pset_Risk
    • RiskName
    • RiskType
    • NatureOfRisk
    • RiskAssessmentMethodology
    • UnmitigatedRiskLikelihood
    • UnmitigatedRiskConsequence
    • UnmitigatedRiskSignificance
    • MitigationPlanned
    • MitigatedRiskLikelihood
    • MitigatedRiskConsequence
    • MitigatedRiskSignificance
    • MitigationProposed
    • AssociatedProduct
    • AssociatedActivity
    • AssociatedLocation
  • Pset_Tolerance
    • ToleranceDescription
    • ToleranceBasis
    • OverallTolerance
    • HorizontalTolerance
    • OrthogonalTolerance
    • VerticalTolerance
    • PlanarFlatness
    • HorizontalFlatness
    • ElevationalFlatness
    • SideFlatness
    • OverallOrthogonality
    • HorizontalOrthogonality
    • OrthogonalOrthogonality
    • VerticalOrthogonality
    • OverallStraightness
    • HorizontalStraightness
    • OrthogonalStraightness
    • VerticalStraightness
  • Pset_Uncertainty
    • UncertaintyBasis
    • UncertaintyDescription
    • HorizontalUncertainty
    • LinearUncertainty
    • OrthogonalUncertainty
    • VerticalUncertainty
  • Qto_BodyGeometryValidation
    • GrossSurfaceArea
    • NetSurfaceArea
    • GrossVolume
    • NetVolume
    • SurfaceGenusBeforeFeatures
    • SurfaceGenusAfterFeatures

5.4.3.35.5 Concept usage

Concept Usage Description
IfcRoot (2)
IfcObjectDefinition (9)
IfcObject (5)
IfcProduct (18)
IfcPositioningElement (1)
Click to show 35 hidden inherited concepts
IfcGrid (3)
Grid Attributes General

No description available.

FootPrint Geometry General

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:

design grid
Figure 5.4.3.35.E — Grid Layout

As shown in Figure 5.4.3.35.E, 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 includes IfcGeometricCurveSet as Items. All grid axes are added as IfcPolyline to the IfcGeometricCurveSet.

representation of a design grid
Figure 5.4.3.35.F — Grid representation

As shown in Figure 5.4.3.35.F, the attributes UAxes and VAxes define lists of IfcGridAxis within the context of the grid. 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.

Spatial Containment General

This concept can be applied to the following resources:

Table 5.4.3.35.I

5.4.3.35.6 Examples

5.4.3.35.7 Formal representation

ENTITY IfcGrid
SUBTYPE OF (IfcPositioningElement);
UAxes : LIST [1:?] OF UNIQUE IfcGridAxis;
VAxes : LIST [1:?] OF UNIQUE IfcGridAxis;
WAxes : OPTIONAL LIST [1:?] OF UNIQUE IfcGridAxis;
PredefinedType : OPTIONAL IfcGridTypeEnum;
END_ENTITY;

5.4.3.35.8 References

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5.4.3.35.9 Changelog

5.4.3.35.9.1 IFC4

  • attribute, PredefinedType
  • where rule, HasPlacement
  • where rule, WR41

5.4.3.35.9.2 IFC4.1

5.4.3.35.9.3 IFC4.2

5.4.3.35.9.4 IFC4.3_DEV_738df036