Rust: bevy_rapier2d 0.22.0 doesn't detect obvious collisions

Siiir · July 20, 2023, 2:08pm

Expectations

I would like to see the following code example spamming "Received collision event: ..." in stdout.

Result

After cargo run you will see two red squares representing colliders of 2 entities. One is hero, the other is enemy.
I believe there's a collision between them as one collider is inside the other.
Unfortunately, bevy_rapier2d doesn't seem to produce any collision events.

Code example

use {bevy::prelude::*, bevy_rapier2d::prelude::*};

fn main() {
    App::new()
        .add_plugins((
            DefaultPlugins,
            RapierPhysicsPlugin::<NoUserData>::pixels_per_meter(100.),
            RapierDebugRenderPlugin::default(),
        ))
        .add_systems(Startup, (spawn_camera, spawn_hero, spawn_enemy))
        .add_systems(Update, (detect_collisions,))
        .run()
}

fn spawn_camera(mut cmds: Commands) {
    cmds.spawn((Camera2dBundle::default(),));
}
fn spawn_hero(mut cmds: Commands) {
    cmds.spawn((
        TransformBundle::default(),
        Collider::cuboid(100., 100.),
        ActiveEvents::COLLISION_EVENTS, // Hero collisions are to always have effect.
        Sensor,
    ));
}
fn spawn_enemy(mut cmds: Commands) {
    cmds.spawn((
        TransformBundle::default(),
        Collider::cuboid(70., 70.),
        // ActiveEvents::COLLISION_EVENTS,
        /* Enemy may collide with other enemies which should have
        no effect */
        Sensor,
    ));
}
/// In future this func. will be replaced with real collision handling (eg. player takes demage)
pub fn detect_collisions(mut collision_events: EventReader<CollisionEvent>) {
    println!("`detect_collisions` system tries to find collisions...");
    for collision_event in collision_events.iter() {
        println!("Received collision event: {:?}", collision_event);
    }
}

I copied the Cargo.toml from my original game to ensure that my bug is reproduced in the same environment.

[package]
name = "bevy_template"
version = "0.1.0"
edition = "2021"

[dependencies]
bevy = {version="0.11", features=["dynamic_linking"]}
bevy-inspector-egui = "0.19.0"
bevy_rapier2d = "0.22.0"
derive_more = "0.99.17"

[profile.dev]
opt-level = 1
[profile.dev.package."*"]
opt-level = 3

From surveying

I understood that Sensors with ActiveEvents::COLLISION_EVENTS should always generate CollisionEvents when one Collider is touching another.

Full scenario

In my game, there's an enemy that slowly moves toward the hero and their bodies start to overlap, but no event is produced at any phase of their convergence.

hax10 · July 21, 2023, 2:40pm

This Bevy example code may help:

github.com

bevyengine/bevy/blob/main/examples/games/breakout.rs

//! A simplified implementation of the classic game "Breakout".

use bevy::{
    prelude::*,
    sprite::collide_aabb::{collide, Collision},
    sprite::MaterialMesh2dBundle,
};

// These constants are defined in `Transform` units.
// Using the default 2D camera they correspond 1:1 with screen pixels.
const PADDLE_SIZE: Vec3 = Vec3::new(120.0, 20.0, 0.0);
const GAP_BETWEEN_PADDLE_AND_FLOOR: f32 = 60.0;
const PADDLE_SPEED: f32 = 500.0;
// How close can the paddle get to the wall
const PADDLE_PADDING: f32 = 10.0;

// We set the z-value of the ball to 1 so it renders on top in the case of overlapping sprites.
const BALL_STARTING_POSITION: Vec3 = Vec3::new(0.0, -50.0, 1.0);
const BALL_SIZE: Vec3 = Vec3::new(30.0, 30.0, 0.0);
const BALL_SPEED: f32 = 400.0;

This file has been truncated. show original

Siiir · July 26, 2023, 9:36am

Unfortunately, this is just an implementation of a simplified collision system/engine.
But what I want is a general purpose, simple and efficient collision engine that can handle 10000 collisions.
I thought bevy_rapier2d would come up to my expectations.