8.12.3.22 IfcPixelTexture

8.12.3.22.1 Semantic 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).
• 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).
• A two-component image specifies the intensity in the first (high) byte and the alpha opacity in the second (low) byte.
• 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).
• 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.

8.12.3.22.2 Entity inheritance

1. • IfcPresentationItem
2. • IfcSurfaceTexture
   • IfcColourRgbList
   • IfcColourSpecification
   • IfcCurveStyleFont
   • IfcCurveStyleFontAndScaling
   • IfcCurveStyleFontPattern
   • IfcIndexedColourMap
   • IfcPreDefinedItem
   • IfcSurfaceStyleLighting
   • IfcSurfaceStyleRefraction
   • IfcSurfaceStyleShading
   • IfcSurfaceStyleWithTextures
   • IfcTextStyleForDefinedFont
   • IfcTextStyleTextModel
   • IfcTextureCoordinate
   • IfcTextureVertex
   • IfcTextureVertexList
3. • IfcPixelTexture
   • IfcBlobTexture
   • IfcImageTexture

8.12.3.22.3 Attributes

8.12.3.22.4 Formal propositions

Width >= 1

Height >= 1

{1 <= ColourComponents <= 4}

SIZEOF(QUERY(temp<* Pixel |
 (BLENGTH(temp) MOD 8 = 0) AND
 (BLENGTH(temp) = BLENGTH(Pixel[1]))
)) = SIZEOF(Pixel)

SIZEOF(Pixel) = (Width * Height)

8.12.3.22.5 Examples

• 

  Tessellation With Pixel Texture

8.12.3.22.6 Formal representation

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};
	PixelAsByteAndSameLength : SIZEOF(QUERY(temp<* Pixel |
 (BLENGTH(temp) MOD 8 = 0) AND
 (BLENGTH(temp) = BLENGTH(Pixel[1]))
)) = SIZEOF(Pixel);
	SizeOfPixelList : SIZEOF(Pixel) = (Width * Height);
END_ENTITY;

8.12.3.22.7 References

• IfcSurfaceTexture