Example to IfcSegmentedReferenceCurve

[evandroAlfieri]

Credit: @RickBrice @civilx64 @peterrdf

[evandroAlfieri]

Ping: @RickBrice @civilx64 @peterrdf @aothms
Looks good?

[RickBrice]

There is a typo in the first paragraph. The "." between IfcCurveSegment and Placement is missing. Otherwise this all looks good to me.

IfcCurveSegmentPlacement.Location

should be

IfcCurveSegment.Placement.Location

[civilx64]

Suggested change

A _IfcSegmentedReferenceCurve_ is a curve defined in a “horizontal distance along base curve, deviating elevation” coordinate system. The _IfcCurveSegment.ParentCurve_ defines the change in cross slope between rail heads over the length of the segment. When the _IfcCurveSegment.Placement.Location_ differs from the _IfcCurveSegmentPlacement.Location_ of the next segment (or the _IfcSegmentedReferenceCurve.EndPoint_ for the last segment, if specified), the _IfcCurveSegment.ParentCurve_ also defines the deviating elevation. If the _IfcCurveSegment.Placement.Location_ is the same as for the start of the next segment, the deviating elevation along the length of the segment is constant.

A _IfcSegmentedReferenceCurve_ is a curve defined in a “horizontal distance along base curve, deviating elevation” coordinate system. The _IfcCurveSegment.ParentCurve_ defines the change in cross slope between rail heads over the length of the segment. When the _IfcCurveSegment.Placement.Location_ differs from the _IfcCurveSegment.Placement.Location_ of the next segment, the _IfcCurveSegment.ParentCurve_ also defines the deviating elevation. If the _IfcCurveSegment.Placement.Location_ is the same as for the start of the next segment, the deviating elevation along the length of the segment is constant.

[aothms]

I actually would prefer to remove all duplication with the entity definition itself.

Suggested change

A _IfcSegmentedReferenceCurve_ is a curve defined in a “horizontal distance along base curve, deviating elevation” coordinate system. The _IfcCurveSegment.ParentCurve_ defines the change in cross slope between rail heads over the length of the segment. When the _IfcCurveSegment.Placement.Location_ differs from the _IfcCurveSegmentPlacement.Location_ of the next segment (or the _IfcSegmentedReferenceCurve.EndPoint_ for the last segment, if specified), the _IfcCurveSegment.ParentCurve_ also defines the deviating elevation. If the _IfcCurveSegment.Placement.Location_ is the same as for the start of the next segment, the deviating elevation along the length of the segment is constant.

This example illustrates the usage of IfcSegmentedReferenceCurve along with an explicit calculation for cosine spiral cant segment.

This will all get hyperlinked so people can click on [IfcSegmentedReferenceCurve] to read the docs.

[evandroAlfieri]

@aothms can we merge this? Note, it's coupled with this buildingSMART/IFC4.3.x-development#913

[civilx64]

There are some minor issues with validation of industry best practices but the syntax, schema, and normative rules all pass in the Validation Service.