|Sketch → Sketcher constraints → Constrain InternalAlignment|
|Show/Hide Internal Geometry, Ellipse|
This constraint aligns lines and points to particular places of a complex sketcher element (there is just one "complex" element so far, the Ellipse).
The constraint requires a lot of effort to use in the way other constraints are. It is hidden in the menu, and not exposed on any toolbars by default. There is a helper tool called Show/Hide Internal Geometry which is exposed on workbenches' toolbars and aimed to completely remove the need to invoke the constraint manually.
The first line that was selected gets aligned to become ellipse's major diameter (but if it is not occupied already by another line, otherwise it will become minor diameter). The second line is aligned to become minor radius. The lines are automatically switched to construction.
Likewise, the first point is constrained to become the first unoccupied focus, and the second point goes to the other focus.
Sketch.addConstraint(Sketcher.Constraint('InternalAlignment:EllipseMajorDiameter', index_of_line, index_of_ellipse)) Sketch.addConstraint(Sketcher.Constraint('InternalAlignment:EllipseMinorDiameter', index_of_line, index_of_ellipse)) Sketch.addConstraint(Sketcher.Constraint('InternalAlignment:EllipseFocus1', index_of_point, 1, index_of_ellipse)) Sketch.addConstraint(Sketcher.Constraint('InternalAlignment:EllipseFocus2', index_of_point, 1, index_of_ellipse))
Introduced in FreeCAD v0.15.4309