IfcCylindricalSurface

Item	SPF	XML	Change	Description
IFC2x3 to IFC4
IfcCylindricalSurface			ADDED

Semantic definitions at the entity

Entity definition

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:

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

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

, or as unit normal by

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.

Attribute definitions

#	Attribute	Type	Cardinality	Description	G
2	Radius	IfcPositiveLengthMeasure		The radius of the cylindrical surface.	X

Inherited definitions from supertypes

Entity inheritance

Attribute inheritance

#	Attribute	Type	Cardinality	Description	G
IfcRepresentationItem
	LayerAssignment	IfcPresentationLayerAssignment @AssignedItems	S[0:1]	Assignment 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.	X
	StyledByItem	IfcStyledItem @Item	S[0:1]	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.	X
IfcGeometricRepresentationItem
IfcSurface
	Dim :=3	IfcDimensionCount		The space dimensionality of IfcSurface. It is always a three-dimensional geometric representation item. IFC4 CHANGE Derived attribute promoted from subtypes.	X
IfcElementarySurface
1	Position	IfcAxis2Placement3D		The position and orientation of the surface. This attribute is used in the definition of the parameterization of the surface.	X
IfcCylindricalSurface
2	Radius	IfcPositiveLengthMeasure		The radius of the cylindrical surface.	X

Formal representations

XML Specification

 <xs:element name="IfcCylindricalSurface" type="ifc:IfcCylindricalSurface" substitutionGroup="ifc:IfcElementarySurface" nillable="true"/>

 <xs:complexType name="IfcCylindricalSurface">

  <xs:complexContent>

   <xs:extension base="ifc:IfcElementarySurface">

    <xs:attribute name="Radius" type="ifc:IfcPositiveLengthMeasure" use="optional"/>

   </xs:extension>

  </xs:complexContent>

 </xs:complexType>

EXPRESS Specification


ENTITY IfcCylindricalSurface

 SUBTYPE OF (IfcElementarySurface);

  Radius : IfcPositiveLengthMeasure;

END_ENTITY;

 EXPRESS-G diagram

	Zylindrische Fläche
	Cylindrical Surface
	Surface cylindrique