Figure 12 — Helmert Transition Segment
The Helmert transition segment is a special case of a fourth order spiral where the curvature rate of change is a quadratic function and the terms are dependent on the length L measured from the inflection point. The parameter value is defined as the deflection i.e. bearing angle &Theta.
The terms for the first half of the segment: QuadraticTerm = L/√2 rest are 0.
Terms for the second half of the segment: QuadraticTerm = -L/√2 LinearTerm = L/4 Constant = -1
SegmentStart is the bearing angle at start and Segment length is the bearing angle at the end of the segment.
Figure 12 illustrates an instance diagram.
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Figure 12 — Helmert Transition Segment |
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<Rules>
<AttributeRule AttributeName="ParentCurve">
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<EntityRule EntityName="IfcSecondOrderPolynomialSpiral">
<AttributeRules>
<AttributeRule RuleID="QuadraticTerm" AttributeName="QuadraticTerm">
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<AttributeRule AttributeName="SegmentStart">
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<AttributeRule AttributeName="SegmentLength">
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