The data model consists of the following:
39  Entities
Defined types
Select types
13  Functions

The schema IfcGeometryResource defines the resources used for geometric representations. The primary application of this resource is for representation of the shape or geometric form of a product model.

NOTE: The definitions of this resource of the IFC model have been taken from the Integrated Resource, part 42 "Integrated generic resources: Geometric and topological representations" of the ISO standard 10303: "Industrial automation systems and integration - Product data representation and exchange". The IfcGeometryResource refers to the clause 4, "Geometry" of the standard. The reference is ISO/IS 10303-42:1994, p. 11-121. The improved definitions of the second edition, ISO/DIS 10303-42:1999 have been used, when applicable.

The definitions taken from ISO/IS 10303-42:1994 have undergone a adaptation process, characterized by:

The following entities, defined in the Integrated Resources, part 43 "Integrated generic resources: Representation structures" have been incorporated in this resource schema:

The geometric representation of the shape is defined following the adaptation of the ISO/CD 10303-42:1992, Industrial Automation Systems and Integration: Product Data Representation and Exchange - Part 42: Integrated Generic Resources. Geometric and Topological Representation. The type, class, and function semantic definition sections follow the adapted wording of the working draft, which is clearly indicated and quoted at each reference. The definitions on geometric and topological representation (when taken from ISO/CD 10303-42:1992) are explicitly excluded from the copyright of buildingSMART International Limited.

For more information on the definitions as defined in the formal ISO standard please refer to: ISO/IS 10303-42:1994, Industrial Automation Systems and Integration: Product Data Representation and Exchange - Part 42: Integrated Generic Resources. Geometric and Topological Representation. The formal standard can be obtained through the local publishers of standards in each individual country.

The following is within the scope of the geometric representation in the current version of the geometry resource:


NOTE: The following definitions are taken from ISO/CD 10303-42:1992. Please refer to ISO/IS 10303-42:1994, p. 3-7 for the final definition of the formal standard.

placement coordinate system:
a rectangular Cartesian coordinate system associated with the placement of a geometric entity in space, used to describe the interpretation of the attributes and to associate a unique parametrisation with curve and surface entities."

Fundamental concepts and assumptions

NOTE: The following fundamental concepts and assumptions are taken from ISO/CD 10303-42:1992. Please refer to ISO/IS 10303-42:1994, p. 12-14 for the final definition of the formal standard.
NOTE: Only the parts relevant to the subset of ISO 10303-42 (which had been incorporated into the IfcGeometryResource) are quoted.

Space Dimensionality
All geometry shall be defined in a right-handed rectangular Cartesian coordinate system with the same units on each axis. A common scheme has been used for the definition of both two-dimensional and three-dimensional geometry. Points and directions exists in both a two-dimensional and a three-dimensional form, these forms are distinguished solely by the presence, or absence, of a third coordinate value. Complex geometric entities are all defined using points and directions from which their space dimensionality can be deduced.

Parameterisation of analytic curves and surfaces
Each curve on surface specified here has a defined parametrisation. In some instances the definitions are in parametric terms. In others, the conic curves and elementary surfaces, the definitions are in geometric terms. In this latter case a placement coordinate system is used to define the parameterisation. The geometric definitions contain some, but not all, of the data required for this. The relevant data to define this placement coordinate system is contained in the axis2_placement (IfcAxis2Placement) associated with the individual curve and surface entities.

The curve entities include lines, some elementary conics, and some referentially or procedurally defined curves. All the curves have a well defined parameterization which makes it possible to trim a curve or identify points on the curve by parameter value. For the conic curves a method of representation is used which separates their geometric form from their orientation and position in space. In each case, the position and orientation information is conveye by an axis2_placement (IfcAxis2Placement). A composite curve entity, which includes the facility to communicate continuity information at the curve-to-curve transition points, is provided for the construction of more complex curves. The offset curve type is a curve defined with reference to other geometry. Separate offset curves entities exist for 2D and 3D applications.

The simple surfaces are the planar surface, a surface of revolution and a surface of linear extrusion. As with curves, all surfaces have an associated standard parameterization. In many cases the surfaces, as defined, are unbounded; it is assumed that they will be bounded either explicitly or implicitly. Explicit bounding is achieved with the bounded surface (here: plane); implicit bounding requires the association of additional topological information to define a face.

Interfaced schemas (5):

( IfcBooleanResult,
( IfcLengthMeasure,
( IfcProfileDef,
( IfcRepresentation);
( IfcTopologicalRepresentationItem,

Entities (39):

Go to Diagram 6 Ifc2DCompositeCurve
Go to Diagram 3 IfcAxis1Placement
Go to Diagram 3 IfcAxis2Placement2D
Go to Diagram 3 IfcAxis2Placement3D
Go to Diagram 5 IfcBoundedCurve
Go to Diagram 7 IfcBoundedSurface
Go to Diagram 3 IfcCartesianPoint
Go to Diagram 4 IfcCartesianTransformationOperator
Go to Diagram 4 IfcCartesianTransformationOperator2D
Go to Diagram 4 IfcCartesianTransformationOperator2DnonUniform
Go to Diagram 4 IfcCartesianTransformationOperator3D
Go to Diagram 4 IfcCartesianTransformationOperator3DnonUniform
Go to Diagram 5 IfcCircle
Go to Diagram 6 IfcCompositeCurve
Go to Diagram 6 IfcCompositeCurveSegment
Go to Diagram 5 IfcConic
Go to Diagram 5 IfcCurve
Go to Diagram 7 IfcCurveBoundedPlane
Go to Diagram 3 IfcDirection
Go to Diagram 7 IfcElementarySurface
Go to Diagram 5 IfcEllipse
Go to Diagram 1 IfcGeometricRepresentationItem
Go to Diagram 5 IfcLine
Go to Diagram 2 IfcMappedItem
Go to Diagram 5 IfcOffsetCurve2D
Go to Diagram 5 IfcOffsetCurve3D
Go to Diagram 3 IfcPlacement
Go to Diagram 7 IfcPlane
Go to Diagram 3 IfcPoint
Go to Diagram 5 IfcPolyline
Go to Diagram 7 IfcRectangularTrimmedSurface
Go to Diagram 2 IfcRepresentationItem
Go to Diagram 2 IfcRepresentationMap
Go to Diagram 7 IfcSurface
Go to Diagram 8 IfcSurfaceOfLinearExtrusion
Go to Diagram 8 IfcSurfaceOfRevolution
Go to Diagram 8 IfcSweptSurface
Go to Diagram 6 IfcTrimmedCurve
Go to Diagram 2 IfcVector

Defined types (1):

Go to Diagram 1 IfcDimensionCount

Select types (3):

Go to Diagram 3 IfcAxis2Placement
Go to Diagram 6 IfcTrimmingSelect
Go to Diagram 2 IfcVectorOrDirection

Enumerations (2):

Go to Diagram 6 IfcTransitionCode
Go to Diagram 6 IfcTrimmingPreference

Functions (13):