IfcSweptDiskSolid

Item	Change	Description
IFC2x3 to IFC4 4.0.0.0
IfcSweptDiskSolid
StartParam	MODIFIED	Instantiation changed to OPTIONAL.
EndParam	MODIFIED	Instantiation changed to OPTIONAL.

Semantic definitions at the entity

Entity definition

An IfcSweptDiskSolid represents the 3D shape by a sweeping representation scheme allowing a two dimensional circularly bounded plane to sweep along a three dimensional Directrix through space.

The StartParam and EndParam parameter are optional, if not provided they default to the start and end of the Directrix. Only if the Directrix is given by a bounded or by a closed curve, it is permissible to omit the values of StartParam and EndParam.

If the transitions between consecutive segments of the Directrix are not tangent continuous, the resulting solid is created by a miter at half angle between the two segments. Informal proposition restricts the permissible angle between two non-tangent continuous segments.

Figure 506 illustrates an example.

Directrix given as IfcIndexedPolyCurve, having linear and circular arc segments, that are tangent continuous between each segments
Directrix being a bounded and open curve
No StartParam and EndParam are provided, start and end default to start and end of the bounded curve of the Directrix

NOTE Although the example shows a Directrix as a poly curve on a planar reference surface, the definition of IfcSweptDiskSolid is not restricted to be based on planer curves. However view definitions or implementer agreements may provide restrictions.

NOTE The geometric item IfcIndexedPolyCurve provides a more compact representation compared with IfcCompositeCurve as is therefore the prefered curve representation for the Directrix.

Figure 506 — Swept disk solid geometry

NOTE Definition according to ISO/CD 10303-42:1992
A swept disk solid is the solid produced by sweeping a circular disk along a three dimensional curve. During the sweeping operation the normal to the plane of the circular disk is in the direction of the tangent to the directrix curve and the center of the disk lies on the directrix. The circular disk may, optionally, have a central hole, in this case the resulting solid has a through hole, or, an internal void when the directrix forms a close curve.

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

HISTORY New entity in IFC2x2.

IFC4 CHANGE The attribute StartParam and EndParam have been made optional.

Informal Propositions:

If the Directrix curve definition is not tangent continuous, the transition between the segments has to be within an acceptable limit of tangent discontinuity. Very sharp edges may result in nearly impossible miter. Implementer agreements may define acceptable limits for tangent discontinuity.
The segments of the Directrix shall be long enough to apply the Radius. In case of an arc segment forming part of the Directrix, its radius shall be greater then the disk Radius
The Directrix shall not be based on an intersecting curve.

Attribute definitions

#	Attribute	Type	Cardinality	Description	G
1	Directrix	IfcCurve		The curve used to define the sweeping operation. The solid is generated by sweeping a circular disk along the Directrix.	X
2	Radius	IfcPositiveLengthMeasure		The Radius of the circular disk to be swept along the directrix. Denotes the outer radius, if an InnerRadius is applied.	X
3	InnerRadius	IfcPositiveLengthMeasure	?	This attribute is optional, if present it defines the radius of a circular hole in the centre of the disk.	X
4	StartParam	IfcParameterValue	?	The parameter value on the Directrix at which the sweeping operation commences. If no value is provided the start of the sweeping operation is at the start of the Directrix. IFC4 CHANGE The attribute has been changed to OPTIONAL with upward compatibility for file-based exchange.	X
5	EndParam	IfcParameterValue	?	The parameter value on the Directrix at which the sweeping operation ends. If no value is provided the end of the sweeping operation is at the end of the Directrix. IFC4 CHANGE The attribute has been changed to OPTIONAL with upward compatibility for file-based exchange.	X

Formal Propositions

Rule	Description
DirectrixDim	The Directrix shall be a curve in three dimensional space.
InnerRadiusSize	If InnerRadius exists then Radius denoting the outer radius shall be greater than InnerRadius.
DirectrixBounded	If the values for StartParam or EndParam are omited, then the Directrix has to be a bounded or closed curve. IFC4 CHANGE New WHERE rule.

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
IfcSolidModel
	Dim :=3	IfcDimensionCount		The space dimensionality of this class, it is always 3.	X
IfcSweptDiskSolid
1	Directrix	IfcCurve		The curve used to define the sweeping operation. The solid is generated by sweeping a circular disk along the Directrix.	X
2	Radius	IfcPositiveLengthMeasure		The Radius of the circular disk to be swept along the directrix. Denotes the outer radius, if an InnerRadius is applied.	X
3	InnerRadius	IfcPositiveLengthMeasure	?	This attribute is optional, if present it defines the radius of a circular hole in the centre of the disk.	X
4	StartParam	IfcParameterValue	?	The parameter value on the Directrix at which the sweeping operation commences. If no value is provided the start of the sweeping operation is at the start of the Directrix. IFC4 CHANGE The attribute has been changed to OPTIONAL with upward compatibility for file-based exchange.	X
5	EndParam	IfcParameterValue	?	The parameter value on the Directrix at which the sweeping operation ends. If no value is provided the end of the sweeping operation is at the end of the Directrix. IFC4 CHANGE The attribute has been changed to OPTIONAL with upward compatibility for file-based exchange.	X

Formal representations

XML Specification

 <xs:element name="IfcSweptDiskSolid" type="ifc:IfcSweptDiskSolid" substitutionGroup="ifc:IfcSolidModel" nillable="true"/>

 <xs:complexType name="IfcSweptDiskSolid">

  <xs:complexContent>

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

    <xs:sequence>

     <xs:element name="Directrix" type="ifc:IfcCurve" nillable="true"/>

    </xs:sequence>

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

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

    <xs:attribute name="StartParam" type="ifc:IfcParameterValue" use="optional"/>

    <xs:attribute name="EndParam" type="ifc:IfcParameterValue" use="optional"/>

   </xs:extension>

  </xs:complexContent>

 </xs:complexType>

EXPRESS Specification


ENTITY IfcSweptDiskSolid

 SUPERTYPE OF(IfcSweptDiskSolidPolygonal)

 SUBTYPE OF (IfcSolidModel);

  Directrix : IfcCurve;

  Radius : IfcPositiveLengthMeasure;

  InnerRadius : OPTIONAL IfcPositiveLengthMeasure;

  StartParam : OPTIONAL IfcParameterValue;

  EndParam : OPTIONAL IfcParameterValue;

 WHERE

  DirectrixDim : Directrix.Dim = 3;
  InnerRadiusSize : (NOT EXISTS(InnerRadius)) OR (Radius > InnerRadius);
  DirectrixBounded : (EXISTS(StartParam) AND EXISTS(EndParam)) OR 

(SIZEOF(['IFCGEOMETRYRESOURCE.IfcConic', 'IFCGEOMETRYRESOURCE.IfcBoundedCurve'] * TYPEOF(Directrix)) = 1);
END_ENTITY;

 EXPRESS-G diagram

	Festkörper - Entlang einer Leitlinie extrudierte Kreisscheibe
	Swept Disk Solid