IFC 4.3.x development

8.12.3.15 IfcFillAreaStyleHatching

Change log

IFC4

additionswhere_rulesPatternStart2D
additionswhere_rulesRefHatchLine2D
deletionswhere_rulesWR21
deletionswhere_rulesWR22
deletionswhere_rulesWR23

8.12.3.15.1 Semantic definitions at the entity

The IfcFillAreaStyleHatching is used to define simple, vector-based hatching patterns, based on styled straight lines. The curve font, color and thickness is given by the HatchLineAppearance, the angle by the HatchLineAngle and the distance to the next hatch line by StartOfNextHatchLine, being either an offset distance or a vector.

NOTE  Definition according to ISO 10303-46:
The fill area style hatching defines a styled pattern of curves for hatching an annotation fill area or a surface.

NOTE  If the hatch pattern involves two (potentially crossing) rows of hatch lines, then two instances of IfcFillAreaStyleHatching should be assigned to the IfcFillAreaStyle. Both share the same (virtual) point of origin of the hatching that is used by the reference hatch line (or the PointOfReferenceHatchLine if there is an offset).

For better control of the hatching appearance, when using hatch lines with other fonts then continuous, the PatternStart allows to offset the start of the curve font pattern along the reference hatch line (if not given, the PatternStart is at zero distance from the virtual point of origin). If the reference hatch line does not go through the origin (of the virtual hatching coordinate system), it can be offset by using the PatternStart .

NOTE  The coordinates of the PatternStart are given relative to the origin of the object coordinate of IfcAnnotationFillArea, or if present, the FillAreaTarget attribute of IfcAnnotationFillArea. The measure values are given in global drawing length units, representing a model hatching, and can be translated into drawing units by the TargetScale for a scale depended IfcGeometricRepresentationSubcontext, if provided.

DEPRECATION  The use of PointOfReferenceHatchLine is deprecated.

Figure 1 illustrates hatch attributes.

hatch example 1 Example 1
This example shows simple hatching given by using a curve font "continuous" at HatchLineAppearance.

The distance of hatch lines is given by a positive length measure. The angle (here 45' if measures in degree) is provided by HatchLineAngle.

The PatternStart is set to NIL ($) in this example.
hatch example 2 Example 2
This shows hatching from example 1 with using a different curve font at HatchLineAppearance.

The distance of hatch lines is given by a positive length measure, therefore the font pattern start is at a point at the next hatch line given by a vector being perpendicular to the point of origin at the reference hatch line.

The PatternStart is set to NIL ($) in this example.
hatch example 3 Example 3
This example uses hatching from example 2 with a vector to determine the pattern start of the next hatch lines.

The pattern start is the beginning of the first visual curve font pattern segment at IfcCurveFont.CurveFont.

The PatternStart is set to NIL ($) in this example.
hatch example 4 Example 4
This example uses hatching from example 3 where the pattern start is offset from the point of origin at the reference hatch line. That is, the first visible curve font pattern segment now does not start at the point of origin at the reference hatch line.


hatch example 5 Example 5
This example uses hatching from example 4 where the hatch pattern is shifted against the underlying coordinate system.

The point that is mapped to the insertion point of the IfcAnnotationFillAreaOccurrence now has an X and Y offset from the start of the reference hatch line. That is, the reference hatch line now does not go through the insertion point of the hatching.



fig 6 Example 6
This example shows use of IfcFillAreaStyleHatching attributes for two IfcFillAreaStyleHatching's within one IfcFillAreaStyle.

Note that the PatternStart now displaces both the reference hatch line from the point of origin and the start of the curve pattern. This can be used in cases when more than one IfcFillAreaStyleHatching is used in an IfcFillAreaStyle in order to place rows of hatch lines with an offset from each other.

Figure 1 — Fill area style hatching

NOTE  Entity adapted from fill_area_style_hatching defined in ISO10303-46

HISTORY  New entity in IFC2x2.

IFC2x3 CHANGE  The IfcFillAreaStyleHatching has been changed by making the attributes PatternStart and PointOfReferenceHatchLine OPTIONAL. The attribute StartOfNextHatchLine has changed to a SELECT with the additional choice of IfcPositiveLengthMeasure. Upward compatibility for file based exchange is guaranteed.

IFC4 CHANGE  The attribute data type for StartOfNextHatchLine has been changed to be a select of IfcPositiveLengthMeasure and IfcVector.

8.12.3.15.1 Attributes

# Attribute Type Description
IfcRepresentationItem
LayerAssignment SET [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
IfcFillAreaStyleHatching
1 HatchLineAppearance IfcCurveStyle The curve style of the hatching lines. Any curve style pattern shall start at the origin of each hatch line.
2 StartOfNextHatchLine IfcHatchLineDistanceSelect A repetition factor that determines the distance between adjacent hatch lines. The factor can either be defined by a parallel offset, or by a repeat factor provided by IfcVector.



> IFC2x3 CHANGE  The attribute type of StartOfNextHatchLine has changed to a SELECT of IfcPositiveLengthMeasure (new) and IfcOneDirectionRepeatFactor.

> IFC4 CHANGE  The attribute type of StartOfNextHatchLine has changed to a SELECT of IfcPositiveLengthMeasure (new) and IfcVector.





3 PointOfReferenceHatchLineOPTIONAL IfcCartesianPoint A Cartesian point which defines the offset of the reference hatch line from the origin of the (virtual) hatching coordinate system. The origin is used for mapping the fill area style hatching onto an annotation fill area or surface. The reference hatch line would then appear with this offset from the fill style target point.

If not given the reference hatch lines goes through the origin of the (virtual) hatching coordinate system.



> IFC2x3 CHANGE  The usage of the attribute PointOfReferenceHatchLine has changed to not provide the Cartesian point which is the origin for mapping, but to provide an offset to the origin for the mapping. The attribute has been made OPTIONAL.





4 PatternStart OPTIONAL IfcCartesianPoint A distance along the reference hatch line which is the start point for the curve style font pattern of the reference hatch line.

If not given, the start point of the curve style font pattern is at the (virtual) hatching coordinate system.



> IFC2x2 Add2 CHANGE The attribute PatternStart has been made OPTIONAL.





5 HatchLineAngle IfcPlaneAngleMeasure A plane angle measure determining the direction of the parallel hatching lines.

8.12.3.15.2 Entity inheritance

dot_inheritance IfcFillAreaStyleHatching IfcFillAreaStyleHatching IfcGeometricRepresentationItem IfcGeometricRepresentationItem IfcFillAreaStyleHatching->IfcGeometricRepresentationItem IfcGeometricRepresentationItem_children 24 more... IfcGeometricRepresentationItem_children->IfcGeometricRepresentationItem IfcRepresentationItem IfcRepresentationItem IfcGeometricRepresentationItem->IfcRepresentationItem IfcRepresentationItem_children 3 more... IfcRepresentationItem_children->IfcRepresentationItem

8.12.3.15.3 Formal representations

ENTITY IfcFillAreaStyleHatching
 SUBTYPE OF (IfcGeometricRepresentationItem);
	HatchLineAppearance : IfcCurveStyle;
	StartOfNextHatchLine : IfcHatchLineDistanceSelect;
	PointOfReferenceHatchLine : OPTIONAL IfcCartesianPoint;
	PatternStart : OPTIONAL IfcCartesianPoint;
	HatchLineAngle : IfcPlaneAngleMeasure;
 WHERE
	PatternStart2D : NOT(EXISTS(PatternStart)) OR (PatternStart.Dim = 2)
;
	RefHatchLine2D : NOT(EXISTS(PointOfReferenceHatchLine)) OR (PointOfReferenceHatchLine.Dim = 2);
END_ENTITY;