# Adding New Types of Output¶

New particle properties can be added to the particle light cones as follows:

• Add a field to the lightcone_<type>_data struct in lightcone_particle_io.h to store the new quantity
• Modify the lightcone_store_<type> function in lightcone_particle_io.c to set the new struct field from the particle data
• in lightcone_io_make_output_fields(), add a call to lightcone_io_make_output_field() to define the new output

Here, <type> is the particle type: gas, dark_matter, stars, black_hole or neutrino.

To add a new type of HEALPIX map:

• Add a function to compute the quantity in lightcone_map_types.c. See lightcone_map_total_mass() for an example.
• Add a new entry to the lightcone_map_types array in lightcone_map_types.h. This should specify the name of the new map type, a pointer to the function to compute the quantity, and the units of the quantity. The last entry in the array is not used and must have a NULL function pointer to act as an end marker.