Inaccurate collisions when using a lot of `ColliderShape`s with the same height

[daxpedda]

When programming a simple platformer, building a straight path out of many ColliderShapes and having a character walk on it doesn't work.

I am assuming that the issue is that the y-coordinate of every ColliderShape is not exactly the same, because of f32 inaccuracies. So the character walks along the straight path but bumps into a block that isn't exactly on the same y-coordinate as the one before it.

Example code

```rust use bevy::prelude::*; use bevy_rapier2d::prelude::*; const SCALE: f32 = 16.; const PLATFORM_Y: f32 = -8.; const TILES: isize = 100; const CONTROLLER_JUMP_IMPULSE: f32 = 15.; fn main() { let mut app = App::new(); app.add_plugins(DefaultPlugins); app.add_plugin(RapierRenderPlugin); app.add_plugin(RapierPhysicsPlugin::::default()); app.add_startup_system(setup) .add_system(movement); app.run() } #[derive(Component)] struct Controller; fn setup(mut commands: Commands, mut rapier_config: ResMut) { commands .spawn() .insert_bundle(OrthographicCameraBundle::new_2d()); rapier_config.scale = SCALE; commands .spawn() .insert_bundle(RigidBodyBundle { mass_properties: RigidBodyMassPropsFlags::ROTATION_LOCKED.into(), ..Default::default() }) .insert_bundle(SpriteBundle { sprite: Sprite { color: Color::rgb(1., 0., 0.), custom_size: Some(Vec2::new(1. * SCALE, 2. * SCALE)), ..Default::default() }, ..Default::default() }) .insert_bundle(ColliderBundle { shape: ColliderShape::cuboid(0.5, 1.).into(), ..Default::default() }) .insert(ColliderPositionSync::Discrete).insert(Controller); for x in -TILES / 2..TILES / 2 { commands .spawn() .insert_bundle(SpriteBundle { sprite: Sprite { color: Color::rgb(0., 1., 0.), custom_size: Some(Vec2::new(1. * SCALE, 1. * SCALE)), ..Default::default() }, transform: Transform::from_xyz(x as f32 * SCALE, PLATFORM_Y * SCALE, 0.), ..Default::default() }) .insert_bundle(ColliderBundle { shape: ColliderShape::cuboid(0.5, 0.5).into(), position: [x as f32, PLATFORM_Y].into(), ..Default::default() }); } } fn movement( keyboard_input: Res>, mut controller: Query<( &mut RigidBodyForcesComponent, &mut RigidBodyVelocityComponent, &RigidBodyMassPropsComponent, &mut ColliderMaterialComponent, ), With>, ) { let (mut rb_forces, mut rb_vel, rb_mprops, mut co_material) = controller.single_mut(); if keyboard_input.just_pressed(KeyCode::Space) { rb_vel.apply_impulse(rb_mprops, Vec2::new(0., CONTROLLER_JUMP_IMPULSE).into()); } let mut x_axis = 0.; if keyboard_input.pressed(KeyCode::A) || keyboard_input.pressed(KeyCode::Left) { x_axis -= 1.; } else if keyboard_input.pressed(KeyCode::D) || keyboard_input.pressed(KeyCode::Right) { x_axis += 1.; } if x_axis == 0. { co_material.friction = 2.; } else { co_material.friction = 0.; x_axis *= 25. * rb_mprops.mass(); rb_forces.force.x = x_axis; } } ```

Somebody else had this issue before, probably with a better explanation of what the issue is about: https://dev.to/sbelzile/making-games-in-rust-part-7-fixing-the-player-randomly-stuck-issue-3mj5.

[brandon-reinhart]

I've run into this as well, but meshing all of the tiles is probably the right solution anyway. Still annoying that it blocks quick n' dirty tests.

[Vrixyz]

I think that's a rapier issue, but I agree it would be convenient to be able to have a smoother experience for "quick n' dirty tests".

Any update on reproduction code is appreciated.