Ecosyste.ms: Awesome

An open API service indexing awesome lists of open source software.

Awesome Lists | Featured Topics | Projects

https://github.com/shnewto/bevy_collider_gen

a library for generating 2D colliders for bevy apps from images
https://github.com/shnewto/bevy_collider_gen

2d bevy collider crates-io gamedev images png rapier rapier2d rust transparency xpbd xpbd2d

Last synced: 5 days ago
JSON representation

a library for generating 2D colliders for bevy apps from images

Awesome Lists containing this project

README 

        
# bevy_collider_gen



[![Crates.io](https://img.shields.io/crates/v/bevy_collider_gen.svg)](https://crates.io/crates/bevy_collider_gen)

[![Crates.io](https://img.shields.io/crates/d/bevy_collider_gen.svg)](https://crates.io/crates/bevy_collider_gen)

[![MIT/Apache 2.0](https://img.shields.io/badge/license-MIT%2FApache-blue.svg)](https://github.com/shnewto/bevy_collider_gen#license)



A library for generating 2d colliders, for bevy apps, from images with transparency



## Specifying your dependency



By default, both bevy_rapier2d and avian2d (formerly bevy_xpbd_2d) are enabled.

This is to help with the out of box experience, specifically,

being able to run both examples and tinker.



But you'll probably only want to just use one of the physics engines supported

so when you use it in your own crate fill in in the `bevy_collider_gen`

dependencies with something like this for `bevy_rapier2d`



```toml

[dependencies.bevy_collider_gen]

# replace "*" with the most recent version of bevy_collider_gen

version = "*"

```



Or this for `avian2d`



```toml

[dependencies.bevy_collider_gen]

# replace "*" with the most recent version of bevy_collider_gen

version = "*"

features = ["avian2d", "parallel"]

default-features = false

```



## Example



![example with a car, terrain, and boulders](https://github.com/shnewto/bevy_collider_gen/blob/main/img/example-default.png?raw=true)



To see this in action you can run the example, with no arguments

it generates a scene with various colliders using PNG's in the `assets/sprite` directory



### bevy_rapier2d



```sh

cargo run --example rapier2d_colliders

```



### avian2d



```sh

cargo run --example avian2d_colliders -F avian2d

```



You can also specify a path to an image yourself the example will attempt to

generate one or more `convex_polyline` colliders for the objects it finds



## About / why



I was looking for a way to iterate on some 2d scenes with colliders

on things with more sophisticated shapes than simple

geometry, I figured there should be enough info in an image with

transparency to generate colliders, and... there is! So i

packaged up my approach here in case anyone else could benefit.



## How it works



😄 head on over to the edges crate to learn more 



## Caveats



- as mentioned here and there in these docs, this implementation requires

  images to have transparency in order to distinguish object from non-object :)

- i imagine for generating things at a larger scale, i.e. colliders

  for sets of sprites bigger than pixel counts in the hundreds, this implementation

  won't be performant to do at runtime. I'll suggest serializing the colliders

  you like and deserializing in your app instead of doing all the number crunching

  on load when you need a performance boost



## Examples of colliders generated for assets/sprite/car.png



(as in pictures of the sort of thing you can expect,

not the runnable bevy app example. That's a couple headings up)



### convex polyline (bevy_raiper2d only)



![convex polyline collider on an upside down car sprite](https://github.com/shnewto/bevy_collider_gen/blob/main/img/convex-polyline.png?raw=true)



### polyline



![polyline collider on an upside down car sprite](https://github.com/shnewto/bevy_collider_gen/blob/main/img/polyline.png?raw=true)



### convex hull



![convex hull collider on an upside down car sprite](https://github.com/shnewto/bevy_collider_gen/blob/main/img/convex-hull.png?raw=true)



### heightfield



The current implementation does best if the image

you're generating a heightfield from is either centered in the image

or spans the entire width of the image...



![heightfield collider on an upside down car sprite](https://github.com/shnewto/bevy_collider_gen/blob/main/img/heightfield.png?raw=true)



### convex decomposition



I didn't add support for convex decomposition directly because when

sprites were small, and collisions were forceful, they were sort of unreliable

(occasional panics because of bounds indexing in rapier's dependencies 💀).

But if you wanted to use convex decomposition colliders you could construct

them with the edge coordinates from your image with something like this



```rust

let sprite_image = image_assets.get(sprite_handle.unwrap()).unwrap();

let edges = Edges::from(sprite_image)

let edge_coordinate_groups = edges.multi_image_edge_translated();

for coords in edge_coordinate_groups {

    let indices: Vec<[u32; 2]> = (0..coords.len()).map(|i| [i as u32, i as u32]).collect();

    let collider = Collider::convex_decomposition(&coords, &indices);

    commands.spawn((

        collider,

        RigidBody::Fixed,

        SpriteBundle {

            texture: sprite_handle.unwrap().clone(),

            ..default()

        },

    ));

}

```



![convex decomposition collider on a car sprite](https://github.com/shnewto/bevy_collider_gen/blob/main/img/convex-decomposition.png?raw=true)



## License



All code in this repository is dual-licensed under either:



- MIT License (LICENSE-MIT or )

- Apache License, Version 2.0 (LICENSE-APACHE or )



At your option.