The reason of this problem is in wrong work of classifier algorithm (see the message ~0080992 to the issue #30354). Therefore, the algorithm of IntTools_FClass2d class has been improved. Namely, now orientation of the polygon is computed from area-criterion instead of angle. As result, some simplification of the method IntTools_FClass2d::Init(...) has been made.
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1. New constructor has been added to the class CSLib_Class2d. It allows applying TColgp_SequenceOfPnt2d.
2. DRAW-commands "addpolygonnode" and "polygonprops" have been created. They are covered by the test case "tests/geometry/2dpolygon/A1".
3. New method Poly::PolygonProperties(...) has been created. See help for detailed information.
4. New testgrid "lowalgos classifier" has been created.
If 2D-curves are requested in intersection result but they cannot be created (by some reason) then the full set of curves (3D and two 2D) is rejected from the intersection result.
1. New testgrid "lowalgos/intss" has been created. It will contain all test cases on geometrical intersection of two surfaces ("intersect" DRAW-command) and two faces ("bopcurves" DRAW-command).
2. New test case for the issue #28493 has been created because the problem is not reproduced on MASTER.
3. Test case (lowalgos/intss/bug24472) for the issue #29501 has been modified in order to check loops of the resulting intersection curves.
