IFC 4.3.0.1 (IFC4X3) development

8.10.2.1 IfcCardinalPointReference

8.10.2.1.1 Semantic definition

An IfcCardinalPointReference is an index reference to significant points of a section profile. This index is used to describe the spatial relationship between the section of a member and a reference axis of the same member.

Indexes 1...9 refer to points at the bounding box of a profile. Indexes 10...19 refer to points defined by geometric centroid (usually centre of gravity) and shear centre, and their combinations with bounding box coordinates. In particular, the following index values are specified in this specification:

  1. bottom left
  2. bottom centre
  3. bottom right
  4. mid-depth left
  5. mid-depth centre
  6. mid-depth right
  7. top left
  8. top centre
  9. top right
  10. geometric centroid
  11. bottom in line with the geometric centroid
  12. left in line with the geometric centroid
  13. right in line with the geometric centroid
  14. top in line with the geometric centroid
  15. shear centre
  16. bottom in line with the shear centre
  17. left in line with the shear centre
  18. right in line with the shear centre
  19. top in line with the shear centre
  20. Lowest point inside of pipe or channel profile (centre of flat bottom)

Other index values are possible but outside the scope of this specification.

Figure 1 illustrates cardinal point values.

arbitrary profile with cardinal points
Figure 8.10.2.1.B illustrates an example extrusion shape with arbitrary profile (IfcArbitraryClosedProfileDef), aligned "mid-depth right" on the member axis. The line of sight follows the extrusion direction Z which points into the drawing plane of above illustration. Hence, "left" is in the positive X direction of the IfcProfileDef. "Top" is in the positive Y direction of the IfcProfileDef.
extrusion shape with arbitrary profile and alignment
Figure 8.10.2.1.B — Cardinal point extrusion

8.10.2.1.2 Formal Propositions

GreaterThanZero<html><body><p>Cardinal point reference shall be greater than zero.</p></body></html>
SELF > 0
Table 8.10.2.1.A

8.10.2.1.3 Formal representation

TYPE IfcCardinalPointReference = INTEGER;
 WHERE
	 GreaterThanZero : SELF > 0;
END_TYPE;

8.10.2.1.4 References

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