GMBullet

Bullet Physics extension for GameMaker

Maintained by: kraifpatrik

Table of Contents

• About
• Features
• Documentation and help
• Building from source
• License
• Links

About

GMBullet is an extension that exposes Bullet physics functions to GameMaker. Its goal is not to be a simplification layer, but instead it tries to match Bullet's API as closely as possible.

Bullet's C++ public API is converted into a C-like code and exposed to GML. For example, instances of classes/structs are created with btClass_create and freed from memory with btClass_destroy. If there's a class btDiscreteDynamicsWorld with a method addRigidBody(body), this becomes btDiscreteDynamicsWorld_addRigidBody(world, body). Classes and structs within a namespace become just the class/struct name prepended with bt, e.g. btCollisionWorld::ClosestRayResultCallback becomes btClosestRayResultCallback. For public members of classes/structs there are getter and setter functions, e.g. for member m_hitPointWorld of btClosestRayResultCallback, there is a getter btClosestRayResultCallback_getHitPointWorld (the m_ prefix is always omitted). In some cases, there are convenience functions like btClass_getSomethingArray(class, outArray) or btClass_createXYZ(x, y, z), so you don't have to create temporary vectors to retrieve data or pass data to functions.

Features

• Collision world
• Collision shapes
  • Box
  • Sphere
  • Capsule
  • Cone
  • Convex hull (🛑 TODO)
  • Cylinder
  • Compound
  • Plane (🛑 TODO)
  • Triangle mesh
    • For dynamic colliders (🛑 TODO)
    • For static colliders
  • Heightfield terrain
• Collision objects
• Discrete dynamics world
• Rigid body
• Constraints
  • ConeTwist
  • Fixed
  • Gear
  • Generic6Dof
  • Generic6DofSpring2
  • Generic6DofSpring
  • Hinge2
  • Hinge
  • Point2Point
  • Slider
  • Typed
  • Universal
• Actions
  • Raycast vehicle
• Ray test
• Sweep test
• Contact tests
• Debug draw
  • In-memory (copy to vertex buffer, submit from GM; slow)
  • OpenGL 2 (🛑 TODO)
  • D3D11 (🛑 TODO)
• Soft body (🚧 WIP)
• Multithreading (🛑 TODO)

Documentation and help

Bullet itself is quite poorly documented and I myself am no Bullet guru, so the absolute most of the GMBullet documentation was generated from source code using ChatGPT 3.5. For the most part, it seems quite good, but sometimes it looks like complete BS. But hey, it's better than nothing! The best way to learn Bullet remains to be using examples included in the official repo. In case you need help with GMBullet, you can join the BlueBurn Discord server, where I will try to do my best to answer your questions. This repo also contains a sample GM project to help you get started.

Building from source

Requires CMake version 3.23 or newer!

# Clone the repo, including submodules
git clone https://github.com/blueburncz/GMBullet.git --recurse-submodules

# Build Bullet
cd GMBullet/bullet3
mkdir build
cd build
cmake .. -DUSE_DOUBLE_PRECISION=ON
cmake --build . --config=Release

# Build GMBullet
cd ../../
mkdir build
cd build
cmake ..
cmake --build . --config=Release

License

Based on Bullet Physics extension for GameMaker: Studio 1.4 by Okapi, available from https://drive.google.com/file/d/1AAn1PfZ8EDkCkJXNkaKyOkp5eJdx2bcM/view under "Finish it, learn from it, do whatever the hell you want" license. Further modifications to the library are available under the MIT license. See LICENSE for the full license text.

Links

• Bullet 3
• BlueBurn Discord
• ChatGPT
• Original project by Okapi