IfcImageTexture

Item	SPF	XML	Change	Description
IFC2x3 to IFC4
IfcImageTexture
Mode	X	X	MODIFIED	Name changed from TextureType to Mode. Type changed from IfcSurfaceTextureEnum to IfcIdentifier. Instantiation changed to OPTIONAL.
Parameter		X	MODIFIED	Name changed from UrlReference to Parameter. Instantiation changed to OPTIONAL. Aggregation changed from NONE to LIST.
URLReference			ADDED
IFC4 Addendum 1
IfcImageTexture
RepeatS			MODIFIED	Type changed from BOOLEAN to IfcBoolean.
RepeatT			MODIFIED	Type changed from BOOLEAN to IfcBoolean.

Semantic definitions at the entity

Entity 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):
1. If all the colours in the palette are greyscale and there is no transparency chunk, it is treated as an intensity texture.
2. If all the colours in the palette are greyscale and there is a transparency chunk, it is treated as an intensity plus opacity texture.
3. >If any colour in the palette is not grey and there is no transparency chunk, it is treated as a full RGB texture.
4. 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:
1. Greyscale files (number of components equals 1) are treated as intensity textures.
2. YCbCr files are treated as full RGB textures.
3. 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.

NOTE Exchange files following the ifcZIP convention may include a sub directory structure for image resources to be stored together with the product data set.

NOTE The definitions of texturing within this standard have been developed in dependence on the texture component of X3D. See ISO/IEC 19775-1.2:2008 X3D Architecture and base components Edition 2, Part 1, 18 Texturing component for the definitions in the international standard.

HISTORY New entity in IFC2x2.

Attribute definitions

#	Attribute	Type	Cardinality	Description	C
6	URLReference	IfcURIReference	[1:1]	Location, provided as an URI, at which the image texture is electronically published.	X

Inherited definitions from supertypes

Entity inheritance

Attribute inheritance

#	Attribute	Type	Cardinality	Description	C
IfcPresentationItem
IfcSurfaceTexture
1	RepeatS	IfcBoolean	[1:1]	The RepeatS field specifies how the texture wraps in the S direction. If RepeatS is TRUE (the default), the texture map is repeated outside the [0.0, 1.0] texture coordinate range in the S direction so that it fills the shape. If RepeatS is FALSE, the texture coordinates are clamped in the S direction to lie within the [0.0, 1.0] range.	X
2	RepeatT	IfcBoolean	[1:1]	The RepeatT field specifies how the texture wraps in the T direction. If RepeatT is TRUE (the default), the texture map is repeated outside the [0.0, 1.0] texture coordinate range in the T direction so that it fills the shape. If RepeatT is FALSE, the texture coordinates are clamped in the T direction to lie within the [0.0, 1.0] range.	X
3	Mode	IfcIdentifier	[0:1]	The Mode attribute is provided to control the appearance of a multi textures. The mode then controls the type of blending operation. The mode includes a MODULATE for a lit appearance, a REPLACE for a unlit appearance, and variations of the two. NOTE The applicable values for the Mode attribute are determined by view definitions or implementer agreements. It is recommended to use the modes described in ISO/IES 19775-1.2:2008 X3D Architecture and base components Edition 2, Part 1. See 18.4.3 MultiTexture for recommended values.	X
4	TextureTransform	IfcCartesianTransformationOperator2D	[0:1]	The TextureTransform defines a 2D transformation that is applied to the texture coordinates. It affects the way texture coordinates are applied to the surfaces of geometric representation itesm. The 2D transformation supports changes to the size, orientation, and position of textures on shapes. Mirroring is not allowed to be used in the IfcCartesianTransformationOperator	X
5	Parameter	IfcIdentifier	L[1:?]	The Parameter attribute is provided to control the appearance of a multi textures. The applicable parameters depend on the value of the Mode attribute. NOTE The applicable values for the list of Parameter attributes are determined by view definitions or implementer agreements. It is recommended to use the source and the function fields described in ISO/IES 19775-1.2:2008 X3D Architecture and base components Edition 2, Part 1. See 18.4.3 MultiTexture for recommended values. By convention, Parameter[1] shall then hold the source value, Parameter[2] the function value, Parameter[3] the base RGB color for select operations, and Parameter[4] the alpha value for select operations.	X
	IsMappedBy	IfcTextureCoordinate @Maps	S[0:?]	Texture coordinates, either provided by a corresponding list of texture vertices to vertex-based geometric items or by a texture coordinate generator, that applies the surface texture to the surfaces of the geometric items. IFC4 CHANGE New attribute added at the end of the attribute list.	X
	UsedInStyles	IfcSurfaceStyleWithTextures @Textures	S[0:?]		X
IfcImageTexture
6	URLReference	IfcURIReference	[1:1]	Location, provided as an URI, at which the image texture is electronically published.	X

Formal representations

XSD Specification

 <xs:element name="IfcImageTexture" type="ifc:IfcImageTexture" substitutionGroup="ifc:IfcSurfaceTexture" nillable="true"/>

 <xs:complexType name="IfcImageTexture">

  <xs:complexContent>

   <xs:extension base="ifc:IfcSurfaceTexture">

    <xs:attribute name="URLReference" type="ifc:IfcURIReference" use="optional"/>

   </xs:extension>

  </xs:complexContent>

 </xs:complexType>

EXPRESS Specification


ENTITY IfcImageTexture

 SUBTYPE OF (IfcSurfaceTexture);

  URLReference : IfcURIReference;

END_ENTITY;

 EXPRESS-G diagram

	Textur - als URL verlinkt
	Image Texture
	Texture d'image