I obtained very interesting results using the existing structures of GOCAD to build a grid and fill it with velocity values. Many improvements can be added to the small program I implemented. I think that the interface produced here with GOCAD could be very useful since it allows the building of grids and especially 3-D grids from very complex models.
Some modifications could be brought to the definition of the grid object for geophysical purposes to make it more efficient and more convenient to use. Currently the maximum number of bytes that can be dynamically allocated limits the size of the output grid.