8.12.3.17 IfcImageTexture
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
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- IfcSurfaceTexture
- IfcColourRgbList
- IfcColourSpecification
- IfcCurveStyleFont
- IfcCurveStyleFontAndScaling
- IfcCurveStyleFontPattern
- IfcIndexedColourMap
- IfcPreDefinedItem
- IfcSurfaceStyleLighting
- IfcSurfaceStyleRefraction
- IfcSurfaceStyleShading
- IfcSurfaceStyleWithTextures
- IfcTextStyleForDefinedFont
- IfcTextStyleTextModel
- IfcTextureCoordinate
- IfcTextureVertex
- IfcTextureVertexList
8.12.3.17.3 Attributes
# | Attribute | Type | Description |
---|---|---|---|
IfcSurfaceTexture (7) | |||
Click to show 7 hidden inherited attributes Click to hide 7 inherited attributes | |||
IfcImageTexture (1) | |||
6 | URLReference | IfcURIReference |
Location, provided as an URI, at which the image texture is electronically published. |
8.12.3.17.4 Examples
8.12.3.17.5 Formal representation
ENTITY IfcImageTexture SUBTYPE OF (IfcSurfaceTexture); URLReference : IfcURIReference; END_ENTITY;