getv3 returns vertex values of the Ith function attached to 3D mesh M3 for cells in the specified CHUNK. The CHUNK may be a list of cell indices, in which case getv3 returns a 2x2x2x(CHUNK.shape) list of vertex coordinates. CHUNK may also be a mesh-specific data structure used in the slice3 routine (see "slice3: Plane and Isosurface Slices of a 3-D mesh" on page 65), in which case getv3 may return a (ni)x(nj)x(nk) array of vertex values. For meshes which are logically rectangular or consist of several rectangular patches, this is up to 8 times less data, with a concomitant performance advantage. Use getv3 when writing slicing functions for slice3.
getv3_rect does the job for a regular rectangular mesh.
getv3_irreg, for an irregular mesh, returns a 3-list whose elements are: