Slight modification of binary coordinates format

[jmborr]

The binary coordinates format supported by fast_protein_cluster is the almost same as the binpos coordinates of AMBER 7, the only difference being that the binpos coordinates file also contains the number of atoms per frame at the very beginning of the file.
binpos coordinates is supported to VMD, which can be used to translate from any other trajectory file formate to binpos and then fed into fast_protein_cluster.