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	C
2	Radius	IfcPositiveLengthMeasure	[1:1]	The radius of the cylindrical surface.	X

Inherited definitions from supertypes

Entity inheritance

Attribute inheritance

#	Attribute	Type	Cardinality	Description	C
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.	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.	X
IfcGeometricRepresentationItem
IfcSurface
	Dim :=3	IfcDimensionCount	[1:1]	The space dimensionality of IfcSurface. It is always a three-dimensional geometric representation item.	X
IfcElementarySurface
1	Position	IfcAxis2Placement3D	[1:1]	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	[1:1]	The radius of the cylindrical surface.	X

Formal representations

XSD 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