Crash in Project()

[kintel]

Manifold::Project() sometimes causes a crash inside Clipper2.
The crash is deterministic and reproducible by passing specific data to Manifold.

I couldn't find any existing test cases for Project(), but the mesh in question can be reconstructed from this example:
openscad/openscad#5139

Stack trace (from openscad/openscad#5137):

EXC_BAD_ACCESS (code=1, address=0x84)

OpenSCAD!Clipper2Lib::ClipperBase::Split(Clipper2Lib::Active&, Clipper2Lib::Point<long long> const&) (/Users/kintel/code/OpenSCAD/openscad/build/_deps/clipper2-src/CPP/Clipper2Lib/src/clipper.engine.cpp:2746)
OpenSCAD!Clipper2Lib::ClipperBase::UpdateEdgeIntoAEL(Clipper2Lib::Active*) (/Users/kintel/code/OpenSCAD/openscad/build/_deps/clipper2-src/CPP/Clipper2Lib/src/clipper.engine.cpp:1742)
OpenSCAD!Clipper2Lib::ClipperBase::DoHorizontal(Clipper2Lib::Active&) (/Users/kintel/code/OpenSCAD/openscad/build/_deps/clipper2-src/CPP/Clipper2Lib/src/clipper.engine.cpp:2650)
OpenSCAD!Clipper2Lib::ClipperBase::ExecuteInternal(Clipper2Lib::ClipType, Clipper2Lib::FillRule, bool) (/Users/kintel/code/OpenSCAD/openscad/build/_deps/clipper2-src/CPP/Clipper2Lib/src/clipper.engine.cpp:2098)
OpenSCAD!Clipper2Lib::ClipperD::Execute(Clipper2Lib::ClipType, Clipper2Lib::FillRule, std::__1::vector<std::__1::vector<Clipper2Lib::Point<double>, std::__1::allocator<Clipper2Lib::Point<double> > >, std::__1::allocator<std::__1::vector<Clipper2Lib::Point<double>, std::__1::allocator<Clipper2Lib::Point<double> > > > >&, std::__1::vector<std::__1::vector<Clipper2Lib::Point<double>, std::__1::allocator<Clipper2Lib::Point<double> > >, std::__1::allocator<std::__1::vector<Clipper2Lib::Point<double>, std::__1::allocator<Clipper2Lib::Point<double> > > > >&) (/Users/kintel/code/OpenSCAD/openscad/build/_deps/clipper2-src/CPP/Clipper2Lib/include/clipper2/clipper.engine.h:602)
OpenSCAD!Clipper2Lib::ClipperD::Execute(Clipper2Lib::ClipType, Clipper2Lib::FillRule, std::__1::vector<std::__1::vector<Clipper2Lib::Point<double>, std::__1::allocator<Clipper2Lib::Point<double> > >, std::__1::allocator<std::__1::vector<Clipper2Lib::Point<double>, std::__1::allocator<Clipper2Lib::Point<double> > > > >&) (/Users/kintel/code/OpenSCAD/openscad/build/_deps/clipper2-src/CPP/Clipper2Lib/include/clipper2/clipper.engine.h:593)
OpenSCAD!Clipper2Lib::Union(std::__1::vector<std::__1::vector<Clipper2Lib::Point<double>, std::__1::allocator<Clipper2Lib::Point<double> > >, std::__1::allocator<std::__1::vector<Clipper2Lib::Point<double>, std::__1::allocator<Clipper2Lib::Point<double> > > > > const&, Clipper2Lib::FillRule, int) (/Users/kintel/code/OpenSCAD/openscad/build/_deps/clipper2-src/CPP/Clipper2Lib/include/clipper2/clipper.h:111)
OpenSCAD!manifold::CrossSection::CrossSection(std::__1::vector<std::__1::vector<glm::vec<2, float, (glm::qualifier)0>, std::__1::allocator<glm::vec<2, float, (glm::qualifier)0> > >, std::__1::allocator<std::__1::vector<glm::vec<2, float, (glm::qualifier)0>, std::__1::allocator<glm::vec<2, float, (glm::qualifier)0> > > > > const&, manifold::CrossSection::FillRule) (/Users/kintel/code/OpenSCAD/openscad/submodules/manifold/src/cross_section/src/cross_section.cpp:278)
OpenSCAD!manifold::Manifold::Impl::Project() const (/Users/kintel/code/OpenSCAD/openscad/submodules/manifold/src/manifold/src/face_op.cpp:319)
OpenSCAD!manifold::Manifold::Project() const (/Users/kintel/code/OpenSCAD/openscad/submodules/manifold/src/manifold/src/manifold.cpp:814)
OpenSCAD!ManifoldGeometry::project() const (/Users/kintel/code/OpenSCAD/openscad/src/geometry/manifold/ManifoldGeometry.cc:209)
OpenSCAD!GeometryEvaluator::projectionNoCut(ProjectionNode const&) (/Users/kintel/code/OpenSCAD/openscad/src/geometry/GeometryEvaluator.cc:974)

[pca006132]

if you update to the latest version of clipper2, does it work?

[kintel]

I haven't tried, but it's worth a try. Nevertheless, it wouldn't hurt adding a test for Project(), to make it easier to test things like this without doing it via OpenSCAD.

[elalish]

I did add Project() to a couple of samples tests: Bracelet and Sponge4. But yes, a dedicated test is also a good idea. Any chance you can dump out a GLB or OBJ we can test with?

[kintel]

OpenSCAD crashes on projection() import("file.obj") with this OBJ file.
projection() in OpenSCAD currently just calls Manifold::Project()

Note: This is slimmed down from the GEB example in OpenSCAD: https://github.com/openscad/openscad/blob/master/examples/Advanced/GEB.scad

# OpenSCAD obj exporter
v -2 -0.7 -0.1
v -2 -0.7 0
v -1.9 -0.7 -0.1
v -1.9 -0.6901 -0.1
v -1.9 -0.7 0
v -1.9 -0.6901 0
v -2 -1 3
v -1.9 -1 3
v -2 -1 4
v -1.9 -1 4
v -1.9 -0.6901 3
v -1.9 -0.6901 4
v -1.7 -0.6901 3
v -1.7 -0.6901 3.2
v -2 0 -0.1
v -2 0 0
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v -2 0 4
v -1.7 0 3
v -1.7 0 3.2
v -1 -0.6901 -0.1
v -1 -0.6901 0
v -1 -0.6901 3.2
v -1 -0.6901 4
v -1 0 -0.1
v -1 0 0
v -1 0 3.2
v -1 0 4
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