# 8.12.3.21 IfcIndexedTriangleTextureMap

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## 8.12.3.21.1 Semantic definition

The IfcIndexedTriangleTextureMap provides the mapping of the 2-dimensional texture coordinates to the surface onto which it is mapped. It is used for mapping the texture to triangles of the IfcTriangulatedFaceSet.

The IfcIndexedTriangleTextureMap defines an index into an indexed list of texture coordinates. The TexCoordIndex is a two-dimensional list, where

• first dimension is the unbounded list of faces corresponding to the list of triangles defined by CoordIndex at IfcTriangulatedFaceSet;
• second dimension is the fixed list of three indices to texture vertices corresponding to the fixed list of indices to vertices at IfcTriangulatedFaceSet

The TexCoords defined at supertype IfcIndexedTextureMap are a two-dimensional list of texture coordinates provided by two parameter values. Each index of the second dimension list of TexCoordIndex points to a texture vertex in TexCoords.

Figure 1 shows the use of IfcTriangulatedFaceSet with textures.

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.))

IfcIndexedTriangleTextureMap.TexCoordsIndex:
((1 4 3), (1 2 4), (3 1 4), (4 1 2), (8 7 6), (6 7 5), (4 3 2), (2 3 1), (5 8 7), (8 5 6), (2 4 3), (3 1 2))

IfcTextureVertexList.TexCoordsList:
((0. -0.5), (1. -0.5), (0. 1.5), (1. 1.5), (0. 0.), (0. 1.), (1. 0.), (1. 1.))


## 8.12.3.21.4 Formal representation

ENTITY IfcIndexedTriangleTextureMap
SUBTYPE OF (IfcIndexedTextureMap);
TexCoordIndex : OPTIONAL LIST [1:?] OF LIST [3:3] OF IfcPositiveInteger;
END_ENTITY;