Simple offset algorithm (BRepOffset_MakeSimpleOffset) is improved to handle the case when bspline surface has imprecise singularity at one of sides (when side is degenerated but not exactly to one point).
In such case, the algorithm tries to collapse all poles of singular side of the surface to the same point; this allows avoiding flapping of normal due to small fluctuations of surface.
If face being offset contains degenerated edges, then check for singularity is done using position and tolerance of corresponding vertices.
In addition, each side is checked with some user-defined tolerance (by default Precision::Confusion()); this helps to process cases when no edge is located at that side or if such edge is not encoded as degenerated.
New parameter Tolerance is introduced for that in BRepOffset_MakeSimpleOffset class.
Tests added:
bugs modelg_7 bug28968 - on isolated faces as reported in the issue, mostly for visual check (absence of loops)
offset simple F01-05 - on original shells, checking tolerances of resulting shell
New topology-preserving offset algorithm has been added. It allows to construct offset shape of build solid.
test cases have been added.
Documentation has been updated to be up to date.
Minor corrections.
Grid is renamed for simplification purposes.
Old constructors are restored with Standard_DEPRECATED macros.
