IFC (IFC4X3) development IfcIndexedColourMap Semantic definition

The IfcIndexedColourMap provides the assignment of colour information to individual faces. It is used for colouring faces of tessellated face sets. The IfcIndexedColourMap defines an index into an indexed list of colour information. The Colours are a two-dimensional list of colours provided by three RGB values. The ColourIndex attribute corresponds to the CoordIndex of the IfcTessellatedFaceSet defining the corresponding index list of faces. The Opacity attribute provides the alpha channel for all faces of the tessellated face set.

Figure 1 shows a diagram of IfcTriangulatedFaceSet with a colour per face.

Figure shows a diagram of IfcPolygonalFaceSet with a colour per face.
Figure illustrates an instance of IfcTriangulatedFaceSet
figure example values
Figure — Indexed colour map for triangulated face set
  • IfcTriangulatedFaceSet.CoordIndex: ((1,6,5),(1,2,6), (6,2,7), (7,2,3), (7,8,6), (6,8,5), (5,8,1), (1,8,4), (4,2,1), (2,4,3), (4,8,7), (7,3,4))
  • IfcCartesianPointList.CoordList: ((0.,0.,0.), (1.,0.,0.), (1.,1.,0.), (0.,1.,0.), (0.,0.,2.), (1.,0.,2.), (1.,1.,2.), (0.,1.,2.))
  • IfcIndexedColourMap.ColourIndex: (1, 1, 2, 2, 3, 3, 1, 1, 1, 1, 1, 1, )
  • IfcColourRgbList.ColourList: ((1.,0.,0.), (0.,1.,0.), (1.,1.,0.))
Table Entity inheritance Attributes

# Attribute Type Description
IfcIndexedColourMap (4)
1 MappedTo IfcTessellatedFaceSet

Reference to the IfcTessellatedFaceSet to which it applies the colours and alpha channel.

2 Opacity OPTIONAL IfcNormalisedRatioMeasure

The opacity value that applies equally to all faces of the tessellated face set. 1.0 means opaque, and 0.0 completely transparent. If not provided, 1.0 is assumed (all colours are opaque).

3 Colours IfcColourRgbList

Indexable list of lists of triples, representing RGB colours.

4 ColourIndex LIST [1:?] OF IfcPositiveInteger

Indices into the IfcColourRgbList for each face of the IfcTriangulatedFaceSet. The colour is applied uniformly to the indexed face.

Table Examples Formal representation

ENTITY IfcIndexedColourMap
 SUBTYPE OF (IfcPresentationItem);
	MappedTo : IfcTessellatedFaceSet;
	Opacity : OPTIONAL IfcNormalisedRatioMeasure;
	Colours : IfcColourRgbList;
	ColourIndex : LIST [1:?] OF IfcPositiveInteger;
END_ENTITY; References

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