"short" list of
Gravity's various features:
- A three-dimensional simulated universe as big
as the real one; plenty of space to build in.
- Up to 1,000 "planets" with mass
and 10,000 "asteroids" without mass in one simulation.
- There's also a user-guidable "satellite" for
- If you think your computer can handle it, you can bump the planet limit up to 10,000 and the asteroid limit to 100,000 to do
really gigantic simulations.
- Many modifiable properties for
- Mass, radius, and color.
- Drag-generating atmospheres.
- Dark matter clouds (for building realistic
- Dynamic mass, radius, and color (for making
evolving stars, or other non-static objects).
- Arbitrary acceleration or deceleration.
- Multiple integration methods and tools:
- Euler, for quick and simple simulation.
- Runge-Kutta 4, the default, for slightly
slower but more accurate simulation.
- A multistep method, for extra speed in
solar system simulations.
- Barnes-Hut, for running simulations with
thousands of gravitating objects.
- Add in a bit of general relativity to make
black holes more realistic.
- Collisions can be turned on or off, and an
optional smoothing length helps prevent planets from behaving
unrealistically in giant simulations.
- Total control of (simulated) time:
- Pause or restart
simulations any number of times.
- Run simulations in
real-time, a multiple of real-time, or with a regular timestep.
- Timesteps can range from fractions of a
nanosecond to hundreds of trillions of years.
- Reverse time to "rewind" an event.
- A built-in 3D graphics system--no DirectX,
OpenGL, or fancy graphics
- Visual display tools:
- Names, acceleration, velocities, paths, and
orbits of planets.
- Background stars for decoration and
- The classic morphing grid for
- Two-color 3D anaglyphic mode, for viewing
simulations with 3D glasses.
- The Barnes-Hut tree (if you're using it).
- And, numerical display tools:
- The current simulated time, date, and time
- Every concievable bit of information about
a particular planet or group of planets:
- Mass and radius, and their rates of change.
- Atmosphere and dark matter properties.
- The size of its event horizon and
photon sphere (for black holes).
- Location, velocity, and acceleration
relative to the origin, user viewpoint, or planet being orbited.
- Orbital elements: eccentricity,
inclination, semi-major axis, longitude of the ascending node, argument
of periapsis, true anomaly, and period.
- All of the above planet properties can be
graphed with respect to time--or each other--for several planets at
- Record simulations as .avi video files, or
compact files to play back within Pixel Gravity. (All videos on this site were recorded within the program.)
- Make your own tutorials to teach things to
Pixel Gravity also has some handy editing tools to make it easier to
- Two clicks create a basic planet; a few more
creates one of many predesigned objects.
- Clicking and dragging in various ways can
move planets around, or
change their masses, radii, or velocities while the simulation
is running (or while it isn't).
- Keyboard commands can stop groups of planets
(together or individually), freeze them in place, or merge them
- Cut, copy, and
paste planets within or between simulations.
- Orbit creation:
- Create a circular orbit between two planets
in two clicks...
- ...or an elliptical orbit with one click and
- With a few more clicks, create a circular or
elliptical orbit between two groups of planets.
- A keyboard command can automatically send a
group of planets into mutual orbit.
- Massless "asteroid" placement tools:
- Automatically arrange masses of asteroids
into spheres, belts, or rings and send them all into orbit around a
planet with a few clicks. Or, just place them one at a time.
- Position asteroids visually, or at defined
physical distances from their central planet.
- Edit groups of asteroids by color, or by the
planet they're attached to.
- Turn asteroids into planets, or vice versa;
this lets you position planets with the asteroid tools, or asteroids
with the planet tools.
- The "camera" from which you view everything
can move freely, point at any planet or group of planets, or even ride
around on a planet's surface.
- Use mouse movements, the keyboard, or both to
zoom around through space.
- The "wormhole" tool lists all the planets in
an orbit-based hierarchy, and, unsurprisingly, lets you teleport
- Set the camera to automatically rotate to
make cinematic simulations and videos.
- Backups and mistake-prevention:
- The current simulation is saved periodically
and reloaded when you restart the program.
- Most actions can be undone if you change your
mind, or redone if you change your mind again. An unlimited number of
undos are saved with the current simulation, so you can go back or
forward to any point in the process of building it.
- And when you want to get precise:
- Measure distances between planets or groups
with a limitless-length ruler.
- Set the mass, radius, atmosphere height and
density, or dark matter height and density of any planet or group by
typing in whatever number you want.
- Set the X/Y/Z location and velocity of any
planet or group, or set their orbital elements.
- Change the gravitational constant, or other
constants used to measure masses and distances.