IFC 4.3.x development

8.9.3.30 IfcCylindricalSurface

Change log

IFC4

added

8.9.3.30.1 Semantic definitions at the entity

The cylindrical surface is a surface unbounded in the direction of z. Bounded cylindrical surfaces are defined by using a subtype of IfcBoundedSurface with BasisSurface being a cylindrical surface.

NOTE 1  A bounded cylindrical surface can be defined by an IfcRectangularTrimmedSurface with BasisSurface being the cylindrical surface and U1 = 0°, U2 = 360° and V1 = lower bound in z, V2 = upper bound in z (if the plane angle measure is degree). A bounded cylindrical arc surface is provided with |U1 - U2| < 360° (assuming the Usense and Vsense agree to the sense of the basis surface).

NOTE 2  A non-rectangular bounded cylindrical surface, e.g. the surface of a round wall underneath a sloped roof, cab be defined by an IfcCurveBoundedSurface with IfcBoundaryCurve's, being a collection of p-curve segments. A p-curve is curve which lies on the basis of a surface and is defined in the parameter space of that surface.

The inherited attributes are interpreted as

  • SELF\IfcElementarySurface.Position defines the location and orientation of the cylindrical surface.
  • SELF\IfcElementarySurface.Position.Location definesd a point on the axis of the cylindrical surface.
  • SELF\IfcElementarySurface.Position.P[3] defines the direction of the axis of the cylindrical surface.

NOTE Definition according to ISO/CD 10303-42:1992
A cylindrical surface is a surface at a constant distance (the radius) from a straight line. A cylindrical surface is defined by its radius and its orientation and location. The data is to be interpreted as follows:

C = Position.Location
x = Position.P[1]
y = Position.P[2]
z = Position.P[3]
R = Radius
and the surface is parameterized as:

formula where the parametric range is -∞ < u,v < ∞ .

In the above parameterization the length unit for the unit vectors z is equal to that of the radius R. In the placement coordinate system defined above, the surface is represented by the equation S = 0, where

formula The positive direction of the normal to the surface at any point on the surface is given by

formula, or as unit normal by

formula

The direction of the normal is away from the axis of the cylinder.

NOTE  Entity adapted from cylindrical_surface defined in ISO 10303-42.

HISTORY  New entity in IFC4.

8.9.3.30.1 Attributes

# Attribute Type Description
IfcRepresentationItem
LayerAssignmentSET [0:1] OF IfcPresentationLayerAssignment FOR AssignedItemsAssignment of the representation item to a single or multiple layer(s). The LayerAssignments can override a LayerAssignments of the IfcRepresentation it is used within the list of Items.

> IFC2x3 CHANGE  The inverse attribute LayerAssignments has been added.

> IFC4 CHANGE  The inverse attribute LayerAssignment has been restricted to max 1. Upward compatibility for file based exchange is guaranteed.
StyledByItem SET [0:1] OF IfcStyledItem FOR Item Reference to the IfcStyledItem that provides presentation information to the representation, e.g. a curve style, including colour and thickness to a geometric curve.



> IFC2x3 CHANGE  The inverse attribute StyledByItem has been added.
IfcGeometricRepresentationItem
IfcSurface
Dim INVALID The space dimensionality of IfcSurface. It is always a three-dimensional geometric representation item.

> IFC4 CHANGE Derived attribute promoted from subtypes.
IfcElementarySurface
1 Position IfcAxis2Placement3D The position and orientation of the surface. This attribute is used in the definition of the parameterization of the surface.
IfcCylindricalSurface
2 Radius IfcPositiveLengthMeasure The radius of the cylindrical surface.

8.9.3.30.2 Entity inheritance

dot_inheritance IfcCylindricalSurface IfcCylindricalSurface IfcElementarySurface IfcElementarySurface IfcCylindricalSurface->IfcElementarySurface IfcElementarySurface_children 3 more... IfcElementarySurface_children->IfcElementarySurface IfcSurface IfcSurface IfcElementarySurface->IfcSurface IfcSurface_children 3 more... IfcSurface_children->IfcSurface IfcGeometricRepresentationItem IfcGeometricRepresentationItem IfcSurface->IfcGeometricRepresentationItem IfcGeometricRepresentationItem_children 24 more... IfcGeometricRepresentationItem_children->IfcGeometricRepresentationItem IfcRepresentationItem IfcRepresentationItem IfcGeometricRepresentationItem->IfcRepresentationItem IfcRepresentationItem_children 3 more... IfcRepresentationItem_children->IfcRepresentationItem

8.9.3.30.3 Formal representations

ENTITY IfcCylindricalSurface
 SUBTYPE OF (IfcElementarySurface);
	Radius : IfcPositiveLengthMeasure;
END_ENTITY;