IFC 4.3.x development

8.12.3.18 IfcIndexedColourMap

Change log

IFC4

added

8.12.3.18.1 Semantic definitions at the entity

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 the use of IfcTriangulatedFaceSet with colours per face.

"IfcIndexedColourMap_01"

 

IfcIndexedColourMap_example-01

 

Figure 2 illustrates an IfcTriangulatedFaceSet represented by
  • 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.))

Figure 2 — Indexed colour map geometry

 

HISTORY  New entity in IFC4.

8.12.3.18.1 Attributes

#Attribute Type Description
IfcPresentationItem
IfcIndexedColourMap
1MappedTo IfcTessellatedFaceSet Reference to the IfcTessellatedFaceSet to which it applies the colours and alpha channel.
2Opacity OPTIONAL IfcNormalisedRatioMeasureThe the opacity value, that applies equaly 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 opque).

> 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.
3Colours IfcColourRgbList Indexable list of lists of quadruples, representing RGB colours.
4ColourIndexLIST [1:?] OF IfcPositiveInteger Index into the IfcColourRgbList for each face of the IfcTriangulatedFaceSet. The colour is applied uniformly to the indexed face.

8.12.3.18.2 Entity inheritance

dot_inheritance IfcIndexedColourMap IfcIndexedColourMap IfcPresentationItem IfcPresentationItem IfcIndexedColourMap->IfcPresentationItem IfcPresentationItem_children 16 more... IfcPresentationItem_children->IfcPresentationItem

8.12.3.18.3 Formal representations

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