---
name: "gyotoy"
section: "1"
platform: "linux"
package: "yorick-gyoto"
version: "2.0.2-6+b2"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/gyotoy"
---

# gyotoy(1)

visualize one geodesic in Kerr metric

## NAME

Gyotoy - visualize one geodesic in Kerr metric

## SYNOPSIS

gyotoy \[*input.xml*\]

## DESCRIPTION

Gyoto is a framework for computing geodesics in curved space-times. The **gyotoy** utility program uses this framework to compute and display a single geodesic (the trajectory of a massive or mass-less particle) in Kerr metric.

**gyotoy** takes as optional argument a scenery description in XML format (*input.xml*). This scenery must contain a Astrobj section of kind Star. Alternatively, a default scenery is loaded.

The user can then interactively select initial parameters and redraw the geodesic as many time as needed. the Projection parameters allow rotating the view and various menu entries are rather self-explanatory. Entries in the File menu allow saving the display as an image file, saving the parameters as an XML description, or saving the geodesic's coordinates in an ASCII file.

**gyotoy** is only a small utility to visualise a single geodesic. It can also be invoked from the [**yorick**(1)](/yorick/1.md) prompt for building more complex graphics and for scripting. Have a look at the gyoto.i and gyotoy.i files in **yorick**'s Y\_SITE directory.

A companion program, [**gyoto**(1)](/gyoto/1.md), can be used to compute an entire Gyoto scenery using relativistic ray-tracing.

## ENVIRONMENT

- GYOTO\_PLUGINS

  The "Star" object in Gyoto is part of the standard plug-in. If the GYOTO\_PLUGINS environment variable is set, it must contain at least "stdplug" for **gyotoy** to run properly.

## AUTHOR

Thibaut Paumard \<thibaut.paumard@obspm.fr\> wrote this manual.

## SEE ALSO

[**gyoto**(1)](/gyoto/1.md), [**yorick**(1)](/yorick/1.md)