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8.12.3.17 IfcImageTexture

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8.12.3.17.1 Semantic definition

An IfcImageTexture provides a 2-dimensional texture that can be applied to a surface of an geometric item and that provides lighting parameters of a surface onto which it is mapped. The texture is provided as an image file at an external location for which an URL is provided.

The following definitions from ISO/IEC 19775-1 X3D Architecture and base components (X3D Specification) apply:

  • Greyscale pixels without alpha or simple transparency are treated as intensity textures.
  • Greyscale pixels with alpha or simple transparency are treated as intensity plus alpha textures.
  • RGB pixels without alpha channel or simple transparency are treated as full RGB textures.
  • RGB pixels with alpha channel or simple transparency are treated as full RGB plus alpha textures.
  • If the image specifies colours as indexed-colour (that is, palettes or colourmaps), the following semantics should be used (note that `greyscale' refers to a palette entry with equal red, green, and blue values):
  • If all the colours in the palette are greyscale and there is no transparency chunk, it is treated as an intensity texture.
  • If all the colours in the palette are greyscale and there is a transparency chunk, it is treated as an intensity plus opacity texture.
  • If any colour in the palette is not grey and there is no transparency chunk, it is treated as a full RGB texture.
  • If any colour in the palette is not grey and there is a transparency chunk, it is treated as a full RGB plus alpha texture.
  • Texture nodes that require support for JPEG files shall interpret JPEG files as follows:
  • Greyscale files (number of components equals 1) are treated as intensity textures.
  • YCbCr files are treated as full RGB textures.
  • No other JPEG file types are required. It is recommended that other JPEG files are treated as a full RGB textures.
  • Texture nodes that recommend support for GIF files shall follow the applicable semantics described above for the PNG format.

The Uniform Resource Locator (URL) is a form of an URI and specified in RFC1738 by IETF. It supports resources located on a particular server being accessed by a particular protocol (usually http), and resources located at a local machine.

8.12.3.17.2 Entity inheritance

8.12.3.17.3 Attributes

# Attribute Type Description
IfcSurfaceTexture (7)
Click to show 7 hidden inherited attributes
IfcImageTexture (1)
6 URLReference IfcURIReference

Location, provided as an URI, at which the image texture is electronically published.

Table 8.12.3.17.B

8.12.3.17.4 Examples

8.12.3.17.5 Formal representation

ENTITY IfcImageTexture
SUBTYPE OF (IfcSurfaceTexture);
URLReference : IfcURIReference;
END_ENTITY;

8.12.3.17.6 References

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8.12.3.17.7 Changelog

8.12.3.17.7.1 IFC4

  • attribute UrlReference name, Changed from "UrlReference" to "URLReference"
  • attribute UrlReference type, Changed from "IfcIdentifier" to "IfcURIReference"