GSnap performs volume rendering of the gas component of a simulation by using the methods of smoothed particle hydrodynamics to compute a continuous density field from the particle distribution. Opacity is taken into account during the projection stage so that foreground gas obscures background gas. Custom color maps can be used to map color to the temperature of the gas. Here are a few examples:
Since the stellar particles used in N-body galaxy simulations are meant to represent the underlying distribution of stars in a Monte Carlo sense, GSnap renders the starlight using the same volume rendering technique used to view the gas. The code includes dust extinction and a simple heuristic for stellar evolution to make the colors look a bit more realistic. It is also possible to view the star particles as dust-attenuated points.