Function write_ply(fn,v,f,facecolours) writes the mesh defined by coloured triangles to a .ply file. The file is accepted by Paraview 4.4 (other versions were not checked because they were not at the disposal of the author). (c) 2026 fabien van mook 2026.08.20 release of this file within package "fvm-geometry-ply" under GNU GPLv3+