Agreement on usage of surface colors and override sequence 

Based on          IFC2x3

Initiator            ISG Meeting-Dijon

Effects              Extended Coordination View

Date                    2006 11 24


Since IFC2x3 the use of the property set Pset_Draughting (see CV-2x3-109) is deprecated and it shall no longer be used. The assignment of color to the shape representation (here to the surface style associated to surfaces, surface models, and solid models, being part of the shape representation) is handled by:

    * IfcSurfaceStyle.Styles (pointing to IfcSurfaceStyleShading or subtype IfcSurfaceStyleRendering)

    * NOTE: other entities are not allowed for IfcSurfaceStyle.Styles, see also CV-2x3-127)

It can be assigned to the element having a shape representation via:

    * explicitly (directly attached to geometry) - subtype of IfcGeometricRepresentationItem inverse relationship StyledByItem pointing to IfcStyledItem.Styles (IfcPresentationStyleAssignment) being an IfcSurfaceStyle

    * NOTE: assigning an IfcSurfaceStyle to a presentation layer is not supported, if the curve color is provided by IfcPresentationLayerWithStyle.LayerStyles it can be used as the edge color for wire frame and in absent of any other surface color information also as surface color.

    * implicitly (attached to the material information used for parametric definition of element shape) - IfcMaterial.HasRepresentation (IfcMaterialDefinitionRepresentation) with the attribute Representations refering to IfcStyledRepresentation.Items being IfcStyledItem's. Then IfcStyledItem.Styles (IfcPresentationStyleAssignment) being an IfcSurfaceStyle

Both ways of assigning a surface color are supported for import in the IFC2x3 coordination view. The sequence for overriding is:

    * check for the layer curve color (if available)

    * override it (if available) by the material surface color

    * override it (if available) by the explicit geometric item surface color

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