In some cases, it can be useful to re-use a geometry and optionally a density and/or specific energy grid from a previous model in a new model. For example, one might want to separate the calculation of the temperature/specific energy from the calculation of the images. Two methods are available for this: use_geometry, and use_quantities.
First, you can re-use the geometry (i.e. the definition of the grid, excluding quantities such as density of specific energy) from either a previous input or output file by doing:
m = Model()
m.use_geometry(<filename>)
For example, if you create a model with:
m1 = Model()
m1.set_cartesian_grid([-1., 1.], [-1., 1.], [-1., 1.])
m1.add_density_grid(np.array([[[1.e-10]]]), 'kmh.hdf5')
s = m1.add_point_source()
s.luminosity = lsun
s.temperature = 6000.
m1.set_n_photons(initial=1000, imaging=1000)
m1.write('model1.rtin')
and run the model to produce model1.rtout, then you can create a new model that makes use of the geometry to set up a model with the same grid, but different density values and source properties by doing:
m2 = Model()
m2.use_geometry('model1.rtout')
m2.add_density_grid(np.array([[[2.e-10]]]), 'kmh.hdf5')
s = m2.add_point_source()
s.luminosity = 0.5 * lsun
s.temperature = 6000.
m2.set_n_photons(initial=1000, imaging=1000)
m2.write('model2.rtin')
Similarly, you can also instruct Hyperion to use the same density grid by doing:
m.use_quantities(<filename>, quantities=<quantities to use>,
use_minimum_specific_energy=<bool>, use_dust=<bool>)
In this case, the previous model has to be an output file from Hyperion. By default, both the density and the specific energy from the last iteration of a previous model are used, as well as the setting for the minimum specific energy (if set), and the dust properties. For example, in the above example, you can do:
m2 = Model()
m2.use_geometry('model1.rtout')
m2.use_quantities('model1.rtout')
s = m2.add_point_source()
s.luminosity = lsun
s.temperature = 6000.
m2.set_n_photons(initial=1000, imaging=1000)
m2.write('model2.rtin')
to use the density, specific energy, and dust from model1.rtout. Note however that the specific energy will be recalculated and overwritten unless you disable the calculation of the specific energy:
m2 = Model()
m2.use_geometry('model1.rtout')
m2.use_quantities('model1.rtout')
s = m2.add_point_source()
s.luminosity = lsun
s.temperature = 6000.
m2.set_n_initial_iterations(0) # disable specific energy calculation
m2.set_n_photons(imaging=1000) # don't specify initial number of photons
m2.write('model2.rtin')
Note that you can also use just the density or just the specific energy if you wish, by using the quantities argument, e.g.:
m2.use_quantities('model1.rtout', quantities=['density'])
or:
m2.use_quantities('model1.rtout', quantities=['specific_energy'])
You can disable using the dust from the previous model (in case you want to change it):
m2.use_quantities('model1.rtout', use_dust=False)
and you can also disable using the minimum specific energy:
m2.use_quantities('model1.rtout', use_minimum_specific_energy=False)