Simplified treatment of radiative energy transfer during the simulation:
- Ignoring of radiation.
- Isothermal flow (no energy transport equation).
- Local cooling (in the optically thin).
- Diffusion approximation (in the optically thick).
- Non-local radiation transport along rays, but LTE and grey opacities.
- Non-local radiation transport along rays, but LTE and binned opacities (ODFs).
More sophisticated a posteriori radiation transport for spectrum synthesis.