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$Id: README,v 1.5 2000/01/29 19:49:24 rsmith Exp $

This is the README file for Xplanets.

What is Xplanets?
This program is a simple simulator of a spaceship moving through the solar

The program is simple in the sense that:
- The planets are moving in circular orbits, in a single plane. In the real
  world they are moving in elliptical orbits, which mostly have a tilt
  (also called inclination) with respect to the plane that the earth is
  moving in.

- The spaceship follows the Newtonian physics model. That is, the movement
  of the ship is dictated by the gravity influence from the planets and
  it's own accelleration. 

Xplanets was written by Roland Smith <>

Where to find it
The latest version is always available on the author's software page:

Installation instructions
Instructions how to build and install xplanets are in the INSTALL file.

Using the program

If you start xplanets, you'll see a window with a display of the solar
system. The planets are indicated by colored circles If the picture is
zoomed-in closely enough, the planets are shown to scale. For visibility's
sake, the minimum diameter of a planet in the window is 8 pixels.  If you
click on a planet, a window showing the fundamental data of that planet
shows up. The white lines form the planet show the relavite velociy of the
planet with respect to the spaceship: If the line points at the ship, it is
moving directly toward the planet. The spaceship is indicated by white
circle with a green line. Left is a row of buttons, a data display and a
button and a dial. Below is a slider.

The simulation buttons are:
quit     - end the program
about    - shows the about dialog
reset    - stops the simulation and puts the spaceship in earth orbit
zoom in  - zooms in toward the sun, shows less planets
zoom out - the opposite, show more planets
run      - the simulation is running as long as this toggle-button is down

The data display shows:
- the size of the view window.
- the name of the planet nearest to the ship.
- the distance to that planet
- the relative speed of the planet.

The controls are:
direction     - The direction in which the spaceship accellerates during a
                burn. This is indicated by the green line on the ship. The
                direction can be changed by the spin button, or by clicking
                or dragging the mouse in the display window. 
accelleration - This scale sets the accelleration of the spaceship, between
                1G and 3G, that is 1 to 3 times the earth's gravity.
burn          - If this toggle button is down, the engines are on and the
                ship is accellerating.

Below is a slider that sets the simulation time accelleration factor. Since
space journeys can take a long time, you can use this slider to speed up
the simulation.