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resphys

Simple 2D AABB only game collision detection/resolution engine

by Rybek

1 unstable release

0.1.0 Sep 30, 2020

Apache-2.0

46KB
1K SLoC

Resphys

Simple 2D collision detection/resolution library supporting only AABB. Developed primarily to be used in my private projects and as learning opportunity.

The library currently only depenetrates the shapes, without modifying their velocities. Its goal isn't to provide a complete physics simulation, but rather to provide collision detection and resolution for simple games.

API breaking changes definitely will happen. The library is in no way production ready. It might be good enough for a gamejam, but may have some bugs. All issues are highly appreciated, including feedback and bug reports.

Physics solver

A physics solver is the component of physics engine that determines how collision resolution is performed. It's what determines most of the engine's 'feel'.

The solver used is very, very simple. The bodies move on each axis separately, first on x axis, later on y.

Downsides:
  • "skipping corners" when velocity is high (because the movements are done separately), but this behavior requires very high velocities to begin with and can be alleviated by substepping very easily
  • individual steps aren't very precise, but in general that's still precise enough for many games and like the previous issue can be alleviated by substepping
Upsides:
  • easy elimination of so called "ghost collisions"
  • efficiently solving the "bullet through paper" problem (currently only partially, with a tolerance up to two times as high as regular discrete collision detection)
  • no need to use any real-life units

Features

  • Body and collider separation (allows building bodies out of multiple AABBs)
  • Solid colliders and sensors
  • [QoL] Builders for Body (BodyDesc) and Collider (ColliderDesc)
  • User supplied metadata
  • Iteration over Collider's contacts
  • Collision/Overlap event generation
  • Collision mask for Collider's
  • [Optimization] Broadphase
  • Querying the World for overlap with arbitrary AABB
  • Querying the World for overlap with ray (Raycast)
  • [QoL] "Simple" version of the interface
  • Tilemap integration (possibly from different crate)

Inspiration

This library's API is inspired by nphysics, Box2D and to a lesser extent by the currently emerging rapier.

The implementations of most intersection and collision algorithms are heavily based on cute_c2.

Pull requests

All pull requests are welcome, however I want to treat your work with due respect so please file an issue first if it introduces any significant changes to existing functionality.

Dependencies

~6MB
~155K SLoC