Godot Gravity Bodies Plugin

A plugin/addon for Godot which adds support for fairly realistic point gravity physics (currently only in 2D).

Why?

Godots built-in "gravity point" physics can be hard to build around. Some issues I have found are:

• only Area2D can have the physics behaviour attached to it
  • to set this up you have to have a large collision shape on the Area2D for gravity to be detected
• there's a bug which means that gravity isn't realistically calculated https://github.com/godotengine/godot/issues/30575
  • this means you can't setup stable orbits

This plugin offers an alternative way of creating point physics.

Requirements

• Godot 3.x

Getting started

How to install

1. Download the latest release from the releases page
2. Unpack the zip into your project into ./addons/gravity_bodies/
3. Check the plugin has been imported successfully in Godot
   1. go to Project -> Project Settings... -> Plugins -> find Gravity Bodies (and Enable)

Setup

1. Create a new scene in your project with a root node (such as Node2D)
2. Add a gravity body to the root
   1. Add a child node to your root
      1. Either add a GravityBody2D node
      2. Or add a RigidBody2D node and attach the script from res://addons/gravity_bodies/GravityBody2D.gd
   2. Give your new node a collision shape
   3. Give your new node something visual like a sprite
   4. Repeat step 2 (but make sure nodes aren't overlapping
3. Run the project

Each gravity body should be attracted to each other.

Configuration

You can configure how the gravity is setup with the following properties on a GravityBody2D node:

Gravity

This property changes how much this node pulls on other gravity bodies.

I recommend setting the mass property rather than gravity property.

Gravity Distance Scale

Changing this property will produce unpredictable/unrealistic physics so use with caution!

Example: setting this property to 0.5 will reduce the gravity given to another particle by half.

Mass

Similar to changing how much this node pulls on other gravity bodies.

Gravity Scale

Multiplies the gravity applied to this body.

Collision Layers and Masks

Different bodies can be placed on different collision layers / masks to change which bodies attract each other.

Examples

These examples can be tested by running them from the ./examples folder.

SolSystem

https://user-images.githubusercontent.com/7733459/193588358-45dd3faf-88bb-4827-8abc-62a8ce514f36.mp4

BinarySystem

https://user-images.githubusercontent.com/7733459/193589348-c8c3e7c3-a17a-4018-a95c-6153b31cfd7f.mp4

FallTest

https://user-images.githubusercontent.com/7733459/193589621-6d234d04-9083-4446-959b-319bcdd26a78.mp4

GravityDistanceScale

https://user-images.githubusercontent.com/7733459/193590492-e43ade1d-034b-4745-aeea-ca86c97e57b1.mp4

GravityScale

https://user-images.githubusercontent.com/7733459/193590718-14ff0a69-355d-4895-96d7-abc85c0d3507.mp4

Caveats

• the performance of this plugin is likely to be far worse than the built-in gravity
• Gravity Distance Scale feels pretty broken

Mentions

Many thanks to https://github.com/ApocalypticPhosphorus/Godot-3D-Gravity as a base to start from.

Further development

Feel free to submit issues / pull requests though I (the maintainer) will likely have moved on from this project.

The code could quite easily be modified to work in 3D (but I have no need for that right now).