lookup_tables

Marching cubes lookup table.

Only the classic Marching Cubes case table (Lorensen 1987) is kept here — that's all the chmpy numpy MC implementation in mc_numpy.py consumes. The Lewiner topological-correctness tables (TILING, TEST, SUBCONFIG13) that the previous cython port used were stripped along with the cython extension; if/when we want to disambiguate saddle cases we'll pull them back in from the upstream scikit-image source.

The base64 string below decodes to a 256x16 int8 array; entry [case_id] gives up to 5 triangles (3 edge ids each), -1 padded.