CGAL users discussion list

[mperk <>]

Hello CGAL team,

When computing the exact inset of a polygon with /inset_polygon_2/ I receive
the following assertion error:

CGAL error: precondition violation!
Expression : CGAL::sign(a * source.x() + b * source.y() + c) == CGAL::ZERO
File       :
/usr/local/include/CGAL/Arr_geometry_traits/Conic_x_monotone_arc_2.h
Line       : 252
Explanation: 
Refer to the bug-reporting instructions at
https://www.cgal.org/bug_report.html
libc++abi.dylib: terminating with uncaught exception of type
CGAL::Precondition_exception: CGAL ERROR: precondition violation!
Expr: CGAL::sign(a * source.x() + b * source.y() + c) == CGAL::ZERO
File: /usr/local/include/CGAL/Arr_geometry_traits/Conic_x_monotone_arc_2.h
Line: 252

The error occurs in the /_offset_polygon/ function when instantiating an
/X_monotone_curve_2/. The output (std::cout) of the value for /(a *
source.x() + b * source.y() + c)/ is /0.0e0/ which indicates that there
might be some kind of precision error in the offset calculation. I attached
a minimum working example where the error occurs for a polygon with only
three vertices. The expected output is:

/Read an input polygon with 3 vertices. The polygon is simple 1/
/The inset comprises 0 polygon(s)./

Best regards,
Michael

inset_test.cpp
<http://cgal-discuss.949826.n4.nabble.com/file/t376300/inset_test.cpp>  




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