more prism tests

[stevengj]

Would be nice to add some more prism tests. There are some tests that are easier to implement if you use a fixed object (or a set of fixed objects), as a supplement to the random "fuzz testing" in the test-prism.c code.

To start with, we could use some canonical non-convex test object (including some non right-angles), e.g. a C-like shape. Then you could precompute some things like the volume, the intersection of a box with the object, the normal vector at a few points, the result of point-in-prism at a few points (near boundaries and corners), and test against these.

[smartalecH]

I've added a tarball with ~200 tests to NanoComp/meep#864

The tests come from a paper/research group that focuses on point-in-polygon methods. We can selectively choose from those.

[stevengj]

(Don't make the C shape too rounded, since rounded shapes are very special in that subsequent edges are nearly parallel.)

It should be sufficient for now to implement tests for a handful of hard-coded points. We can always add additional test cases later as issues arise.

[stevengj]

It would also be reasonable to use the 200 tabulated tests you mentioned for the 2d point-in-polygon subroutine, but we still need separate tests for polyhedra.