The PLY format is a relatively generic file format designed to store three dimensional data from 3D scanners with the possibility of associating properties to the polygons. Information on this format can be found on wikipedia (see also the External links section). A very efficient C library for reading and writing PLY files in ASCII or binary format is RPly (DisPerSE uses it for PLY files I/O, see files NDnet_PLY_IO.c and NDnet_PLY_IO.h).

A typical header for a PLY file readable by netconv or mse is as follows:

ply
format ascii 1.0
element bbox 1
property list uchar double x0 
property list uchar double delta
element vertex 77595
property float x
property float y
property float z
property double field_value
element face 482867
property list uchar uint vertex_indices
end_header

• -format may be ASCII or little / big endian binary

• -bbox element is used to define a bounding box if available (x0 is its origin and delta its extent)

• -coordinates of the vertices are given as vertex properties labeled x, y, and z or x0, x1, ... (the number of this properties gives the dimension of the embedding space)

• -faces are defined by the property vertex_indices, each element corresponding to a list of vertices. A cell is always supposed to be a simplex, so the number of vertices determine the dimension spanned by the complex (a 2D complex may be embedded in a 3D space).

• -additional properties may be defined for cells and vertices. In particular, a vertex property labeled field_value would be used as input function in mse.