Definition from ISO/CD 10303-42:1992: An ellipse (IfcEllipse) is a conic section defined by the lengths of the semi-major and semi-minor diameters and the position (center or mid point of the line joining the foci) and orientation of the curve. Interpretation of the data shall be as follows:
C = SELF\IfcConic.Position.Locationx = SELF\IfcConic.Position.P[1]y = SELF\IfcConic.Position.P[2]z = SELF\IfcConic.Position.P[3]R1 = SemiAxis1R2 = SemiAxis2
and the ellipse is parameterized as:
The parameterization range is 0 £ u £ 2p (or 0 £ u £ 360 degree). In the placement coordinate system defined above, the ellipse is the equation C = 0, where
The positive sense of the ellipse at any point is in the tangent direction, T, to the curve at the point, where
The inherited Position.Location from IfcConic is the center of the IfcEllipse, and the inherited Position.P[1] from IfcConic the direction of the SemiAxis1.
NOTE Corresponding STEP entity: ellipse. Please refer to ISO/IS 10303-42:1994, p. 39 for the final definition of the formal standard.
HISTORY New class in IFC Release 1.0
Illustration:
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Definition of the IfcEllipse within the (in this case three-dimensional) position coordinate system. |