8.12.3.18 IfcIndexedColourMap

RV ⓘ

AbV ⓘ

8.12.3.18.1 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 8.12.3.18.A shows a diagram of IfcTriangulatedFaceSet with a colour per face. Figure 8.12.3.18.B shows a diagram of IfcPolygonalFaceSet with a colour per face.

IfcIndexedColourMap_01 — Figure 8.12.3.18.A — Indexed colour map for triangulated face sets

IfcIndexedColourMap_02 — Figure 8.12.3.18.B — Indexed colour map for polygonal face sets

IfcIndexedColourMap_03 — Figure 8.12.3.18.C — Indexed colour map for triangulated face set

Figure 8.12.3.18.C illustrates an instance of IfcTriangulatedFaceSet based on the following data:

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.))

8.12.3.18.2 Entity inheritance

- IfcPresentationItem

8.12.3.18.3 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). NOTE The definition of the alpha channel component for opacity follows the new definitions in image processing, where 0.0 means full transparency and 1.0 (or 2^bit depths^ -1) means fully opaque. This is contrary to the definition of transparency in IfcSurfaceStyleShading.
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 8.12.3.18.E

8.12.3.18.4 Examples

Figure 8.12.3.18.D

Tessellation With Individual Colors

8.12.3.18.5 Formal representation

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