  GYOTO, a general relativistic ray-tracing code, is presented. It aims at
computing images of astronomical bodies in the vicinity of compact objects, as
well as trajectories of massive bodies in relativistic environments. This code
is capable of integrating the null and timelike geodesic equations not only in
the Kerr metric, but also in any metric computed numerically within the 3+1
formalism of general relativity. Simulated images and spectra have been
computed for a variety of astronomical targets, such as a moving star or a
toroidal accretion structure. The underlying code is open source and freely
available. It is user-friendly, quickly handled and very modular so that
extensions are easy to integrate. Custom analytical metrics and astronomical
targets can be implemented in C++ plug-in extensions independent from the main
code.
