IfcSphericalSurface

Item	SPF	XML	Change	Description
IFC4 Addendum 2
IfcSphericalSurface			ADDED

Semantic definitions at the entity

Entity definition

The IfcSphericalSurface is a bounded elementary surface. The inherited Position attribute defines the IfcAxisPlacement3D and provides:

SELF\IfcElementarySurface.Position: The location and orientation of the axis system for the primitive.
SELF\IfcElementarySurface.Position.Location: The center of the spherical surface.
SELF\IfcElementarySurface.Position.Position[3]: The z axis points at its positve direction towards the north pole, and by its negative directions towards the south pole.

NOTE Definition according to ISO/CD 10303-42:1992

An IfcSphericalSurface is a type of an elementary surface, which is at a constant distance (the radius) from a central point. A spherical surface is defined by the radius and the location and orientation of the surface.

The data is to be interpreted as follows:

C = Position.Location
x = Position.P[1]
y = Position.P[2]
z = Position.P[3] (axis of spherical surface)
R = Radius

and the surface is parametrised as

σ(u,v) = C + R cos v ((cos u) x + (sin u) y) + R(sin v) z

where the parametrisation range is 0 ≤ u ≤ 360 degrees and -90 ≤ v ≤ 90 degrees. u and v are angular parameters and when numerical values are specified they shall use the current units for plane angle measure.

In the placement coordinate system defined above, the surface is represented by the equation S = 0, where

S(x, y, z) = x² + y² + z² - R².

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

(S_x, S_y, S_z ).

The unit normal is given by

N(u,v) = cos v((cos u)x + (sin u)y) + (sin v)z,

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

HISTORY New entity in IFC4 Addendum 2.

Attribute definitions

#	Attribute	Type	Cardinality	Description	G
2	Radius	IfcPositiveLengthMeasure		The radius of the sphere.	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
IfcSphericalSurface
2	Radius	IfcPositiveLengthMeasure		The radius of the sphere.	X

Formal representations

XML Specification

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

 <xs:complexType name="IfcSphericalSurface">

  <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 IfcSphericalSurface

 SUBTYPE OF (IfcElementarySurface);

  Radius : IfcPositiveLengthMeasure;

END_ENTITY;

 EXPRESS-G diagram