IfcPixelTexture

Item	SPF	XML	Change	Description
IFC2x3 to IFC4
IfcPixelTexture
Mode	X	X	MODIFIED	Name changed from TextureType to Mode. Type changed from IfcSurfaceTextureEnum to IfcIdentifier. Instantiation changed to OPTIONAL.
Parameter	X	X	MODIFIED	Name changed from Width to Parameter. Type changed from IfcInteger to IfcIdentifier. Instantiation changed to OPTIONAL. Aggregation changed from NONE to LIST.
Width		X	MODIFIED	Name changed from Height to Width.
Height		X	MODIFIED	Name changed from ColourComponents to Height.
ColourComponents	X	X	MODIFIED	Name changed from Pixel to ColourComponents. Type changed from BINARY (32) to IfcInteger. Aggregation changed from LIST to NONE.
Pixel			ADDED
IFC4 Addendum 1
IfcPixelTexture
RepeatS			MODIFIED	Type changed from BOOLEAN to IfcBoolean.
RepeatT			MODIFIED	Type changed from BOOLEAN to IfcBoolean.
Pixel			MODIFIED	Type changed from BINARY (32) to IfcBinary.

Semantic definitions at the entity

Entity definition

An IfcPixelTexture provides a 2D image-based texture map as an explicit array of pixel values (list of Pixel binary attributes). In contrary to the IfcImageTexture the IfcPixelTexture holds a 2 dimensional list of pixel color (and opacity) directly, instead of referencing to an URL.

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

The PixelTexture node defines a 2D image-based texture map as an explicit array of pixel values (image field) and parameters controlling tiling repetition of the texture onto geometry.
Texture maps are defined in a 2D coordinate system (s, t) that ranges from 0.0 to 1.0 in both directions. The bottom edge of the pixel image corresponds to the S-axis of the texture map, and left edge of the pixel image corresponds to the T-axis of the texture map. The lower-left pixel of the pixel image corresponds to s=0.0, t=0.0, and the top-right pixel of the image corresponds to s = 1.0, t = 1.0.
The Image field specifies a single uncompressed 2-dimensional pixel image. Image fields contain three integers representing the width, height and number of components in the image, followed by width×height hexadecimal values representing the pixels in the image. Pixel values are limited to 256 levels of intensity (that is, 0x00-0xFF hexadecimal).
1. A one-component image specifies one-byte hexadecimal value representing the intensity of the image. For example, 0xFF is full intensity in hexadecimal (255 in decimal), 0x00 is no intensity (0 in decimal).
2. A two-component image specifies the intensity in the first (high) byte and the alpha opacity in the second (low) byte.
3. Pixels in a three-component image specify the red component in the first (high) byte, followed by the green and blue components (for example, 0xFF0000 is red, 0x00FF00 is green, 0x0000FF is blue).
4. Four-component images specify the alpha opacity byte after red/green/blue (e.g., 0x0000FF80 is semi-transparent blue). A value of 00 is completely transparent, FF is completely opaque, 80 is semi-transparent.
Note that alpha equals (1.0 -transparency), if alpha and transparency each range from 0.0 to 1.0.

HISTORY New entity in IFC2x2.

Attribute definitions

#	Attribute	Type	Cardinality	Description	C
6	Width	IfcInteger	[1:1]	The number of pixels in width (S) direction.	X
7	Height	IfcInteger	[1:1]	The number of pixels in height (T) direction.	X
8	ColourComponents	IfcInteger	[1:1]	Indication whether the pixel values contain a 1, 2, 3, or 4 colour component.	X
9	Pixel	IfcBinary	L[1:?]	Flat list of hexadecimal values, each describing one pixel by 1, 2, 3, or 4 components.	X

Formal Propositions

Rule	Description
MinPixelInS	The minimum number of pixel in width (S coordinate) direction shall be 1.
MinPixelInT	The minimum number of pixel in height (T coordinate) direction shall be 1.
NumberOfColours	The number of color components shall be either 1, 2, 3, or 4.
SizeOfPixelList	The list of pixel shall have exactly width*height members.
PixelAsByteAndSameLength	The binary value provided for each Pixel shall be a multiple of 8 bits. And all pixel shall have the same binary length.

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
IfcPixelTexture
6	Width	IfcInteger	[1:1]	The number of pixels in width (S) direction.	X
7	Height	IfcInteger	[1:1]	The number of pixels in height (T) direction.	X
8	ColourComponents	IfcInteger	[1:1]	Indication whether the pixel values contain a 1, 2, 3, or 4 colour component.	X
9	Pixel	IfcBinary	L[1:?]	Flat list of hexadecimal values, each describing one pixel by 1, 2, 3, or 4 components.	X

Formal representations

XSD Specification

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

 <xs:complexType name="IfcPixelTexture">

  <xs:complexContent>

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

    <xs:attribute name="Width" type="ifc:IfcInteger" use="optional"/>

    <xs:attribute name="Height" type="ifc:IfcInteger" use="optional"/>

    <xs:attribute name="ColourComponents" type="ifc:IfcInteger" use="optional"/>

    <xs:attribute name="Pixel" use="optional">

     <xs:simpleType>

      <xs:restriction>

       <xs:simpleType>

        <xs:list itemType="xs:hexBinary"/>

       </xs:simpleType>

      </xs:restriction>

     </xs:simpleType>

    </xs:attribute>

   </xs:extension>

  </xs:complexContent>

 </xs:complexType>

EXPRESS Specification


ENTITY IfcPixelTexture

 SUBTYPE OF (IfcSurfaceTexture);

  Width : IfcInteger;

  Height : IfcInteger;

  ColourComponents : IfcInteger;

  Pixel : LIST [1:?] OF IfcBinary;

 WHERE

  MinPixelInS : Width >= 1;
  MinPixelInT : Height >= 1;
  NumberOfColours : {1 <= ColourComponents <= 4};
  SizeOfPixelList : SIZEOF(Pixel) = (Width * Height);
  PixelAsByteAndSameLength : SIZEOF(QUERY(temp<* Pixel |
 (BLENGTH(temp) MOD 8 = 0) AND
 (BLENGTH(temp) = BLENGTH(Pixel[1]))
)) = SIZEOF(Pixel);
END_ENTITY;

 EXPRESS-G diagram

	Textur - als Liste der Pixel gegeben
	Pixel Texture