Plugin: dsp_kepler
Author: Tom Smith

The Kepler plugin updates the positions and orientation of all solar system objects based on a Julian date. The Julian date can run either as real time, from a set time, or externally driven. Kepler drives nodes for all the planets under the name of _INERTIAL_REF (for that planet's inertial reference frame), and _BODY_REF (for the frame which is locked to the solar system body as it rotates).

| * -ssdata_dir | directory where relevant data files reside | || | * -start_time | Julian date of the desired start time | | * -time_factor | Scale factor for the rate of time (seconds/second if that makes any sense) | | * -start_time_now | Use the current time as the start time | | * -use_external_time | Tells Kepler not to automatically increment the time, and allow an external source to set it | | * JULIAN.x | The x parameter of the JULIAN node is used to communicate the time to other plugins which need to know the time | | * KEPLER_ORIGIN.parent | The parent of the KEPLER_ORIGIN node is used to specify where NULL should be located within the scene so that the most precision can be available |

The kepler plugin usage is pretty basic since most things are handled automatically. The JULIAN time is the main user interface to the plugin. By default, the plugin uses the current system clock and sets the solar system accordingly. To use a different time, use the "-use_external_time" plugin option shown above, and then set the time in the "x" parameter of the node JULIAN.

You can also elect to have the plugin maintain the time, but initialize it to a certain value using the "-start_time" option. The "-time_factor" option is also available to make propagation occur more quickly or slowly.

Configuration of the plugin is normally done in "${USERDATA}/configs/kepler.cfg". Here the plugin is loaded and options are passed in. You will also notice "kepler_models.cfg" in the "POSTLOAD" section. This is the file that contains the necessary data nodes for the planets and their different frames. This is required.