ThreeBody

ThreeBody is a very nice application that manages to calculate the trajectories of the 3 planets to illustrate the three body problem.
It's a classical question in celestial mechanics. It determines the trajectories in an universe limited to three planets and the law of the universal gravitation.

Lightweight interface with plenty of animation

The application doesn't take long to install and it doesn't need users to complete a complicated setup in order to work. It automatically launches with the trajectory of the three planets and it uses lots of animation to illustrate them.
The background is nice, but it would have been better if the software solution actually used a HD image to make it more appealing to users.

Adjust values and calculate trajectories

You have the option to choose the numerical method for calculations. Pick from fixed or adaptive steps. In addition, you can change the integration and maximum steps, together with the relative error.
The values for the integration step must be lower than 1.00e-6, while the maximum step must be greater. You can enable the visible trajectory for each of the three planets, the colors used by ThreeBody will be different for each of them, to make it easier to distinguish between them.

Print images displayed in ThreeBody

You can adjust the sky size and make some other changes inside the application. Click on a planet to change its radius, mass, position, speed and enable the feature that maintains the zero momentum.
It comes with some settings that you can adjust, like the option to change the background picture and pick the image for the planets. You can also set a start delay of several seconds.

Save pictures and print them

ThreeBody lets you save pictures and make some printer settings, like adjust the size, orientation and margins.
All in all, ThreeBody is a very nice application that lets you calculate the trajectories of 3 planets in order to illustrate the three body problem, as well as make some adjustments and settings.