8.12.3.5 IfcCurveStyle

Style de courbe
Linienstil

An IfcCurveStyle provides the style table for presentation information assigned to geometric curves. The style is defined by a color, a font and a width. The IfcCurveStyle defines curve patterns as model patterns, that is, the distance between visible and invisible segments of curve patterns are given in model space dimensions (that have to be scaled using the target plot scale).

Styles are intended to be shared by multiple IfcStyledItem's, assigning the style to occurrences of (subtypes of) IfcGeometricRepresentationItem's. Measures given to a font pattern or a curve width are given in global drawing length units.

NOTE  global units are defined at the single IfcProject instance, given by UnitsInContext:IfcUnitAssignment, the same units are used for the geometric representation items and for the style definitions.

The measure values for font pattern and curve width apply to the model space with a target plot scale provided for the correct appearance in the default plot scale.. For different scale and projection dependent curve styles a different instance of IfcCurveStyle needs to be used by IfcPresentationStyleAssignment for different IfcGeometricRepresentationSubContext dependent representations.

NOTE  the target plot scale is given by IfcGeometricRepresentationSubContext.TargetScale.

An IfcCurveStyle can be assigned to IfcGeometricRepresentationItem's via the IfcPresentationStyleAssignment through an intermediate IfcStyledItem or IfcAnnotationCurveOccurrence.

NOTE  Definition according to ISO/CD 10303-46:1992
A curve style specifies the visual appearance of curves.
NOTE  Corresponding ISO 10303 name: curve_style. Please refer to ISO/IS 10303-46:1994 for the final definition of the formal standard.
HISTORY  New entity in IFC2x2.

XSD Specification:

 <xs:element name="IfcCurveStyle" type="ifc:IfcCurveStyle" substitutionGroup="ifc:IfcPresentationStyle" nillable="true"/>
 <xs:complexType name="IfcCurveStyle">
  <xs:complexContent>
   <xs:extension base="ifc:IfcPresentationStyle">
    <xs:sequence>
     <xs:element name="CurveFont" nillable="true" minOccurs="0">
      <xs:complexType>
       <xs:group ref="ifc:IfcCurveFontOrScaledCurveFontSelect"/>
      </xs:complexType>
     </xs:element>
     <xs:element name="CurveWidth" nillable="true" minOccurs="0">
      <xs:complexType>
       <xs:group ref="ifc:IfcSizeSelect"/>
      </xs:complexType>
     </xs:element>
     <xs:element name="CurveColour" nillable="true" minOccurs="0">
      <xs:complexType>
       <xs:group ref="ifc:IfcColour"/>
      </xs:complexType>
     </xs:element>
    </xs:sequence>
    <xs:attribute name="ModelOrDraughting" type="xs:boolean" use="optional"/>
   </xs:extension>
  </xs:complexContent>
 </xs:complexType>

EXPRESS Specification:

ENTITY IfcCurveStyle
SUBTYPE OF IfcPresentationStyle;
CurveFont : OPTIONAL IfcCurveFontOrScaledCurveFontSelect;
CurveWidth : OPTIONAL IfcSizeSelect;
CurveColour : OPTIONAL IfcColour;
ModelOrDraughting : OPTIONAL BOOLEAN;
WHERE
MeasureOfWidth : (NOT(EXISTS(CurveWidth))) OR ('IFCMEASURERESOURCE.IFCPOSITIVELENGTHMEASURE' IN TYPEOF(CurveWidth)) OR (('IFCMEASURERESOURCE.IFCDESCRIPTIVEMEASURE' IN TYPEOF(CurveWidth)) AND (CurveWidth = 'by layer'));
IdentifiableCurveStyle : EXISTS(CurveFont) OR EXISTS(CurveWidth) OR EXISTS(CurveColour);
END_ENTITY;

Link to EXPRESS-G diagram EXPRESS-G diagram

Attribute Definitions:

CurveFont : A curve style font which is used to present a curve. It can either be a predefined curve font, or an explicitly defined curve font. Both may be scaled. If not given, then the curve font should be taken from the layer assignment with style, if that is not given either, then the default curve font applies.
CurveWidth : A positive length measure in units of the presentation area for the width of a presented curve. If not given, then the style should be taken from the layer assignment with style, if that is not given either, then the default style applies.
CurveColour : The colour of the visible part of the curve. If not given, then the colour should be taken from the layer assignment with style, if that is not given either, then the default colour applies.
ModelOrDraughting : Indication whether the length measures provided for the presentation style are model based, or draughting based.
IFC4 CHANGE  New attribute.

Formal Propositions:

MeasureOfWidth : The curve width, if provided, shall be given by an IfcPositiveLengthMeasure representing the curve width in the default measure unit, or by an IfcDescriptiveMeasure with the value 'by layer' representing the curve width by the default curve width at the associated layer.
IdentifiableCurveStyle : At minimum one of the three attribute values have to be provided, CurveFont, CurveWidth, CurveColour.

Inheritance Graph:

ENTITY IfcCurveStyle
ENTITY IfcPresentationStyle
Name : OPTIONAL IfcLabel;
ENTITY IfcCurveStyle
CurveFont : OPTIONAL IfcCurveFontOrScaledCurveFontSelect;
CurveWidth : OPTIONAL IfcSizeSelect;
CurveColour : OPTIONAL IfcColour;
ModelOrDraughting : OPTIONAL BOOLEAN;
END_ENTITY;

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