IFC 4.3.1.0 (IFC4X3_ADD1) development

8.12.3.15 IfcFillAreaStyleHatching

AbRV ⓘ

8.12.3.15.1 Semantic definition

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.

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 .

DEPRECATION The use of PointOfReferenceHatchLine is deprecated.

Figure 8.12.3.15.A 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 ($) in this example. Figure 8.12.3.15.B shows hatching from example 1 with using a different curve font at HatchLineAppearance. The distance of hatch lines is given by a positive length measure, therefore the font pattern start is at a point at the next hatch line given by a vector being perpendicular to the point of origin at the reference hatch line. The PatternStart is set to NIL ($) in this example.

Figure 8.12.3.15.C 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.

Figure 8.12.3.15.D 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.

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.

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.

8.12.3.15.5 Formal representation

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;

8.12.3.15.6 References

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8.12.3.15.7 Changelog

8.12.3.15.7.1 IFC4

• where rule, PatternStart2D
• where rule, RefHatchLine2D
• where rule, WR21
• where rule, WR22
• where rule, WR23