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Image/Data Save and Usage

Q:  How do I save the images shown in the Image Panel

On the top of the Image Panel, you can choose “File>Save to Image”, and then save the image in .png/.jpg/.bmp formats.


Q: How can I save the trajectories?

Two steps are required.

step 1: add (or remove) the existing text rays in the Trajectory Database by press the “+” box (or the “-” box)at the bottom of the Control Panel.

step 2: choose “File>Save trajectories to file…” and save all the trajectories in the Trajectory Database in .txt format. The output includes the spacetime co-ordinates in Boyer-Lindquist co-ordinates (t, r, θ, Φ).


The saved files can be loaded by Odyssey_Edu again by using “+…”box.

Q: Where is the default location for saved files?


Q: Can I use the saved images for publications?

Sure. We only ask that users cite the following paper in their publications:

Odyssey: A Public GPU-based Code for General-relativistic Radiative Transfer in Kerr Spacetime” by Hung-Yi Pu, Kiyun Yun, Ziri Younsi, and Suk-Jin Yoon (Astrophysical Journal 2016, 820:105)

Technical details

Q: Which "co-ordinate" is adopted by Odyssey_Edu?

The Kerr spacetime may be described using several different co-ordinate systems. In Odyssey_Edu, the photon trajectories are shown in the Boyer-Lindquist co-ordinate (t, r, θ, Φ).

Q: Where can I find more algorithm details about Odyssey_Edu?

Odyssey Edu follows the same algorithm introduced in section 2 of our paper, except that the trajectory is integrated forward in time (and hence the initial condition has opposite sign).

Q: What science is related to the ray trajectories around black holes?

Geodesics of photons in the Kerr spacetime are essential ingredients in (but not restricted to), for example, studies of the observational appearance of a star, of accretion disks around black holes, calculation of emission line profiles, reverberation measurements, images or light curves of an orbiting hot spot, quasi-periodic oscillations (QPOs), black hole shadow images, and radiative transfer in curved spacetimes.