IFC 4.3.x development

8.9.3.36 IfcIndexedPolyCurve

Change log

IFC4

added

IFC4X3_RC3

additionswhere_rulesConsecutive
deletionswhere_rulesConsecutive

8.9.3.36.1 Semantic definitions at the entity

The IfcIndexedPolyCurve is a bounded curve with only linear and circular arc segments defined by a Cartesian point list and an optional list of segments, providing indices into the Cartesian point list. In the case that the list of Segments is not provided, all points in the IfcCartesianPointList are connected by straight line segments in the order they appear in the IfcCartesianPointList.

In the case that the list of Segments is provided, it is interpreted as such:

  • Segment of type IfcLineIndex: The first index is the start point of the poly line segment, the last index is the end point of the poly line segment. If more than two indices are included, then all intermediate indices define intermediate points of the polyline connected in the order of appearance of the indices;
  • Segment of type IfcArcIndex: The first index is the start point of the circular arc, the second index is a point on arc, the third index is the end point of the circular arc. The three points shall not be co-linear. In case that this informal proposition is not maintained, the arc segment shall be treated as a polyline segment.

EXAMPLE  Figure 2 illustrates a bounded open IfcIndexedPolyCurve having straight and arc segments. In this example, the straight segments only have two points and one edge, however more then two indices into the Cartesian point list can be includes, defining a multi edge polyline segment.

"poly curve with arcs examples"

EXAMPLE  Figure 2 illustrates a bounded open IfcIndexedPolyCurve having only straight segments. In this example, no list of Segments is provided, hence the points are drawn in the order of their appearance in the IfcCartesianPointList.

"poly curve examples"

The IfcIndexedPolyCurve represents an open or a closed curve depending on the following condition:

  • In the case that the list of Segments is provided: If the last index of the last Segment and the first index of the first Segment are identical, then the poly curve is a closed curve, otherwise it is an open curve.
  • In the case that the list of Segments is not provided: If the first and the last Cartesian point in the Cartesian point list are identical, then the poly curve is a closed curve, otherwise it is an open curve.

HISTORY  New entity in IFC4 ADD1

Informal Propositions:

  1. Any two consecutive points of the IfcIndexedPolyCurve shall not be coincident after taking the Precision factor into account, given by the applicable IfcGeometricRepresentationContext.
  2. The three points of any IfcArcIndex segment of the IfcIndexedPolyCurve shall not be colinear after taking the Precision factor into account, given by the applicable IfcGeometricRepresentationContext.

8.9.3.36.1 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
IfcCurve
Dim INVALID The space dimensionality of this abstract class, defined differently for all subtypes, i.e. for IfcLine, IfcConic and IfcBoundedCurve.
IfcBoundedCurve
IfcIndexedPolyCurve
1 Points IfcCartesianPointList A list of points, provided by a point list of either two, or three dimensions, that is used to define the poly curve. If the attribute Segments is not provided, the poly curve is generated as a poly line by connecting the points in the order of their appearance in the point list. If the attribute Segments is provided, the segments determine, how the points are to be used to create straigth and circular arc segments.
2 Segments OPTIONAL LIST [1:?] OF IfcSegmentIndexSelect List of straight line and circular arc segments, each providing a list of indices into the Cartesian point list. Indices should preserve consecutive connectivity between the segments, the start index of the next segment shall be identical with the end index of the previous segment.
3 SelfIntersect OPTIONAL IfcBoolean Indication of whether the curve intersects itself or not; this is for information only.

8.9.3.36.2 Entity inheritance

dot_inheritance IfcIndexedPolyCurve IfcIndexedPolyCurve IfcBoundedCurve IfcBoundedCurve IfcIndexedPolyCurve->IfcBoundedCurve IfcBoundedCurve_children 4 more... IfcBoundedCurve_children->IfcBoundedCurve IfcCurve IfcCurve IfcBoundedCurve->IfcCurve IfcCurve_children 7 more... IfcCurve_children->IfcCurve IfcGeometricRepresentationItem IfcGeometricRepresentationItem IfcCurve->IfcGeometricRepresentationItem IfcGeometricRepresentationItem_children 24 more... IfcGeometricRepresentationItem_children->IfcGeometricRepresentationItem IfcRepresentationItem IfcRepresentationItem IfcGeometricRepresentationItem->IfcRepresentationItem IfcRepresentationItem_children 3 more... IfcRepresentationItem_children->IfcRepresentationItem

8.9.3.36.3 Formal representations

ENTITY IfcIndexedPolyCurve
 SUBTYPE OF (IfcBoundedCurve);
	Points : IfcCartesianPointList;
	Segments : OPTIONAL LIST [1:?] OF IfcSegmentIndexSelect;
	SelfIntersect : OPTIONAL IfcBoolean;
 WHERE
	Consecutive : NOT(EXISTS(Segments)) OR IfcConsecutiveSegments(Segments);
END_ENTITY;