isoSurface uses geometric tolerance for merging points
The isoSurface class (e.g. used in cutting plane sampling) uses a geometric tolerance to convert a cloud of triangles into a mesh. This uses a geometric distance (default 1e-6 of the mesh bounding box; can be supplied externally through 'mergeTol' entry). So
- on meshes with extreme variation in cell size the default tolerance might be too loose and it merges too many points
- there is no check to make sure it does not merge two or three points on the same triangle