Bevy: Despawning causes panics

[katis]

Trying out bevy and started with a player that can shoot bullets. Ran into an issue where spawning more bullets after despawning one causes a panic. Usually need to spawn 2 bullets after one was despawned.
Running on Pop!_OS (basically Ubuntu) with a Ryzen 3700X + GTX TI 1080 and NVIDIA proprietary drivers (version 418.152.00).

Full stacktrace:

thread 'main' panicked at 'no empty slots available in array', /home/katis/.cargo/registry/src/github.com-1ecc6299db9ec823/bevy_render-0.1.0/src/render_graph/nodes/render_resources_node.rs:50:17
stack backtrace:
   0:     0x5576c111ede5 - backtrace::backtrace::libunwind::trace::h75aedf5f78e5147f
                               at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.46/src/backtrace/libunwind.rs:86
   1:     0x5576c111ede5 - backtrace::backtrace::trace_unsynchronized::h18fb73c9ac9ae753
                               at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.46/src/backtrace/mod.rs:66
   2:     0x5576c111ede5 - std::sys_common::backtrace::_print_fmt::h65f97470ff13ec84
                               at src/libstd/sys_common/backtrace.rs:78
   3:     0x5576c111ede5 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::hee061c54ddc9f024
                               at src/libstd/sys_common/backtrace.rs:59
   4:     0x5576c114abdc - core::fmt::write::hfbd2baad61ed21a8
                               at src/libcore/fmt/mod.rs:1117
   5:     0x5576c111af62 - std::io::Write::write_fmt::h72f9bd227f40dc62
                               at src/libstd/io/mod.rs:1508
   6:     0x5576c1121a80 - std::sys_common::backtrace::_print::h2d2cd8fe02feb5fa
                               at src/libstd/sys_common/backtrace.rs:62
   7:     0x5576c1121a80 - std::sys_common::backtrace::print::h801b12991252ba7c
                               at src/libstd/sys_common/backtrace.rs:49
   8:     0x5576c1121a80 - std::panicking::default_hook::{{closure}}::h25fc1fbf3b63b5c8
                               at src/libstd/panicking.rs:198
   9:     0x5576c11217cc - std::panicking::default_hook::h62c897957a5e0f26
                               at src/libstd/panicking.rs:217
  10:     0x5576c11220c3 - std::panicking::rust_panic_with_hook::hb8a276f163c59810
                               at src/libstd/panicking.rs:526
  11:     0x5576c0d0a579 - std::panicking::begin_panic::h0beeb81efb5d4d3e
                               at /rustc/6c8927b0cf80ceee19386026cf9d7fd4fd9d486f/src/libstd/panicking.rs:456
  12:     0x5576c0be6fef - bevy_render::render_graph::nodes::render_resources_node::BufferArrayStatus::get_or_assign_index::hf492a4e8068393bd
                               at /home/katis/.cargo/registry/src/github.com-1ecc6299db9ec823/bevy_render-0.1.0/src/render_graph/nodes/render_resources_node.rs:50
  13:     0x5576c09419d4 - bevy_render::render_graph::nodes::render_resources_node::UniformBufferArrays<T>::setup_uniform_buffer_resources::h23b3ebd594ea1e94
                               at /home/katis/.cargo/registry/src/github.com-1ecc6299db9ec823/bevy_render-0.1.0/src/render_graph/nodes/render_resources_node.rs:237
  14:     0x5576c0946324 - bevy_render::render_graph::nodes::render_resources_node::render_resources_node_system::{{closure}}::h069fa2c5b403b0b2
                               at /home/katis/.cargo/registry/src/github.com-1ecc6299db9ec823/bevy_render-0.1.0/src/render_graph/nodes/render_resources_node.rs:465
  15:     0x5576bff8eb40 - <bevy_wgpu::renderer::wgpu_render_resource_context::WgpuRenderResourceContext as bevy_render::renderer::render_resource_context::RenderResourceContext>::write_mapped_buffer::h9b86a35a19441905
                               at /home/katis/.cargo/registry/src/github.com-1ecc6299db9ec823/bevy_wgpu-0.1.0/src/renderer/wgpu_render_resource_context.rs:521
  16:     0x5576c0945cf2 - bevy_render::render_graph::nodes::render_resources_node::render_resources_node_system::hd89f3a6ec4b76504
                               at /home/katis/.cargo/registry/src/github.com-1ecc6299db9ec823/bevy_render-0.1.0/src/render_graph/nodes/render_resources_node.rs:456
  17:     0x5576c0952055 - core::ops::function::Fn::call::h79589152f08ca8eb
                               at /rustc/6c8927b0cf80ceee19386026cf9d7fd4fd9d486f/src/libcore/ops/function.rs:72
  18:     0x5576c094b9e0 - core::ops::function::impls::<impl core::ops::function::FnMut<A> for &F>::call_mut::h26087de917b9f979
                               at /rustc/6c8927b0cf80ceee19386026cf9d7fd4fd9d486f/src/libcore/ops/function.rs:253
  19:     0x5576c095fe3e - <Func as bevy_ecs::system::into_system::IntoQuerySystem<(),(Ra,Rb),(A,)>>::system::{{closure}}::he622a81dc394759e
                               at /home/katis/.cargo/registry/src/github.com-1ecc6299db9ec823/bevy_ecs-0.1.0/src/system/into_system.rs:218
  20:     0x5576c09616f5 - <bevy_ecs::system::into_system::SystemFn<State,F,ThreadLocalF,Init,SetArchetypeAccess> as bevy_ecs::system::system::System>::run::h80c50a1167514fce
                               at /home/katis/.cargo/registry/src/github.com-1ecc6299db9ec823/bevy_ecs-0.1.0/src/system/into_system.rs:61
  21:     0x5576c1011eab - bevy_ecs::schedule::schedule::Schedule::run::hb87ad000ecd04d9c
                               at /home/katis/.cargo/registry/src/github.com-1ecc6299db9ec823/bevy_ecs-0.1.0/src/schedule/schedule.rs:138
  22:     0x5576c0b85aee - bevy_render::render_graph::system::render_graph_schedule_executor_system::h2a0d7e2a50852843
                               at /home/katis/.cargo/registry/src/github.com-1ecc6299db9ec823/bevy_render-0.1.0/src/render_graph/system.rs:13
  23:     0x5576c0b1c7f1 - core::ops::function::FnMut::call_mut::h4a365c5db4c3016e
                               at /rustc/6c8927b0cf80ceee19386026cf9d7fd4fd9d486f/src/libcore/ops/function.rs:154
  24:     0x5576c0b7a261 - <F as bevy_ecs::system::into_system::ThreadLocalSystemFn>::run::h9463824cb56a5ccf
                               at /home/katis/.cargo/registry/src/github.com-1ecc6299db9ec823/bevy_ecs-0.1.0/src/system/into_system.rs:339
  25:     0x5576c0c0241e - <F as bevy_ecs::system::into_system::IntoThreadLocalSystem>::thread_local_system::{{closure}}::ha71ab17bfba9a2ef
                               at /home/katis/.cargo/registry/src/github.com-1ecc6299db9ec823/bevy_ecs-0.1.0/src/system/into_system.rs:315
  26:     0x5576c0bf39dd - <bevy_ecs::system::into_system::SystemFn<State,F,ThreadLocalF,Init,SetArchetypeAccess> as bevy_ecs::system::system::System>::run_thread_local::hdbc9fa8077dbea8e
                               at /home/katis/.cargo/registry/src/github.com-1ecc6299db9ec823/bevy_ecs-0.1.0/src/system/into_system.rs:65
  27:     0x5576c1028505 - bevy_ecs::schedule::parallel_executor::ExecutorStage::run::h9786ed11a62fd705
                               at /home/katis/.cargo/registry/src/github.com-1ecc6299db9ec823/bevy_ecs-0.1.0/src/schedule/parallel_executor.rs:341
  28:     0x5576c1025fa6 - bevy_ecs::schedule::parallel_executor::ParallelExecutor::run::hf5facd7b347d899c
                               at /home/katis/.cargo/registry/src/github.com-1ecc6299db9ec823/bevy_ecs-0.1.0/src/schedule/parallel_executor.rs:59
  29:     0x5576c0ff6d69 - bevy_app::app::App::update::h0315008cd34b2776
                               at /home/katis/.cargo/registry/src/github.com-1ecc6299db9ec823/bevy_app-0.1.0/src/app.rs:60
  30:     0x5576c0475e27 - bevy_winit::winit_runner::{{closure}}::hcbc86eecf88e0b24
                               at /home/katis/.cargo/registry/src/github.com-1ecc6299db9ec823/bevy_winit-0.1.1/src/lib.rs:140
  31:     0x5576c0458a27 - cart_tmp_winit::platform_impl::platform::sticky_exit_callback::hdcf862bed15c3d24
                               at /home/katis/.cargo/registry/src/github.com-1ecc6299db9ec823/cart-tmp-winit-0.22.2/src/platform_impl/linux/mod.rs:703
  32:     0x5576c04a55b8 - cart_tmp_winit::platform_impl::platform::x11::EventLoop<T>::run_return::hf1c2b05e50990cfe
                               at /home/katis/.cargo/registry/src/github.com-1ecc6299db9ec823/cart-tmp-winit-0.22.2/src/platform_impl/linux/x11/mod.rs:295
  33:     0x5576c04a688e - cart_tmp_winit::platform_impl::platform::x11::EventLoop<T>::run::h6a3136f014c8237b
                               at /home/katis/.cargo/registry/src/github.com-1ecc6299db9ec823/cart-tmp-winit-0.22.2/src/platform_impl/linux/x11/mod.rs:386
  34:     0x5576c045869d - cart_tmp_winit::platform_impl::platform::EventLoop<T>::run::h5659dfb0477b8dd8
                               at /home/katis/.cargo/registry/src/github.com-1ecc6299db9ec823/cart-tmp-winit-0.22.2/src/platform_impl/linux/mod.rs:620
  35:     0x5576c04a0c28 - cart_tmp_winit::event_loop::EventLoop<T>::run::hc16a08826b9d182d
                               at /home/katis/.cargo/registry/src/github.com-1ecc6299db9ec823/cart-tmp-winit-0.22.2/src/event_loop.rs:149
  36:     0x5576c0474f65 - bevy_winit::winit_runner::hf19c3205ee0515e7
                               at /home/katis/.cargo/registry/src/github.com-1ecc6299db9ec823/bevy_winit-0.1.1/src/lib.rs:48
  37:     0x5576c04a150f - core::ops::function::Fn::call::haf41d002572a373c
                               at /rustc/6c8927b0cf80ceee19386026cf9d7fd4fd9d486f/src/libcore/ops/function.rs:72
  38:     0x5576c0fe1e4a - <alloc::boxed::Box<F> as core::ops::function::Fn<A>>::call::ha48473f3ba1c9d15
                               at /rustc/6c8927b0cf80ceee19386026cf9d7fd4fd9d486f/src/liballoc/boxed.rs:1088
  39:     0x5576c0ff6efd - bevy_app::app::App::run::h035f3be4dc4782ee
                               at /home/katis/.cargo/registry/src/github.com-1ecc6299db9ec823/bevy_app-0.1.0/src/app.rs:73
  40:     0x5576c0ff389b - bevy_app::app_builder::AppBuilder::run::hc9e6a953797c57f1
                               at /home/katis/.cargo/registry/src/github.com-1ecc6299db9ec823/bevy_app-0.1.0/src/app_builder.rs:43
  41:     0x5576bff08560 - my_game::main::h4cdc7192abc0a2c5
                               at src/main.rs:122
  42:     0x5576bfefffbb - std::rt::lang_start::{{closure}}::hf853ee00a16bb423
                               at /home/katis/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/src/libstd/rt.rs:67
  43:     0x5576c1122563 - std::rt::lang_start_internal::{{closure}}::hbd178e645b70b347
                               at src/libstd/rt.rs:52
  44:     0x5576c1122563 - std::panicking::try::do_call::hd9e76f93421bce23
                               at src/libstd/panicking.rs:348
  45:     0x5576c1122563 - std::panicking::try::h6776eea046a81bd7
                               at src/libstd/panicking.rs:325
  46:     0x5576c1122563 - std::panic::catch_unwind::hd9dfb4dd4c6fb7d1
                               at src/libstd/panic.rs:394
  47:     0x5576c1122563 - std::rt::lang_start_internal::h47278b515c002423
                               at src/libstd/rt.rs:51
  48:     0x5576bfefff97 - std::rt::lang_start::hfee2c021bf1639f3
                               at /home/katis/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/src/libstd/rt.rs:67
  49:     0x5576bff085ba - main
  50:     0x7f31eb3fa0b3 - __libc_start_main
  51:     0x5576bfef9c2e - _start
  52:                0x0 - <unknown>

Process finished with exit code 101

Code:

use bevy::{prelude::*, render::pass::ClearColor};

type Seconds = f64;

struct Player;

struct ShootDelay {
    delay: Seconds,
    last: Seconds,
}

struct Velocity(Vec2);

impl ShootDelay {
    fn can_shoot_next(&self, time: Seconds) -> bool {
        (self.delay + self.last) <= time
    }
}

struct DestroyOutOfBounds;

fn setup(mut commands: Commands, mut materials: ResMut<Assets<ColorMaterial>>) {
    commands
        .spawn(Camera2dComponents::default())
        .spawn(UiCameraComponents::default())
        .spawn(SpriteComponents {
            material: materials.add(Color::rgb(0.2, 0.2, 0.8).into()),
            translation: Translation(Vec3::new(0.0, -250.0, 0.0)),
            sprite: Sprite {
                size: Vec2::new(64.0, 64.0),
            },
            ..Default::default()
        })
        .with(Player)
        .with(ShootDelay {
            delay: 0.3,
            last: 0.,
        });
}

fn input(
    mut commands: Commands,
    mut materials: ResMut<Assets<ColorMaterial>>,
    time: Res<Time>,
    kb: Res<Input<KeyCode>>,
    mouse: Res<Input<MouseButton>>,
    mut query: Query<(&Player, &mut ShootDelay, &mut Translation)>,
) {
    for (_, mut shoot_delay, mut translation) in &mut query.iter() {
        let mut delta_x = 0.0;
        if kb.pressed(KeyCode::A) {
            delta_x -= 1.0;
        }
        if kb.pressed(KeyCode::D) {
            delta_x += 1.0;
        }

        let mut delta_y = 0.0;
        if kb.pressed(KeyCode::W) {
            delta_y += 1.0;
        }
        if kb.pressed(KeyCode::S) {
            delta_y -= 1.0;
        }

        if mouse.just_pressed(MouseButton::Left)
            || (mouse.pressed(MouseButton::Left)
                && shoot_delay.can_shoot_next(time.seconds_since_startup))
        {
            shoot_delay.last = time.seconds_since_startup;
            commands
                .spawn(SpriteComponents {
                    material: materials.add(Color::rgb(0.7, 0.4, 0.3).into()),
                    sprite: Sprite {
                        size: Vec2::new(10., 10.),
                    },
                    translation: Translation(translation.0),
                    ..Default::default()
                })
                .with(Velocity(Vec2::new(0., 200.)))
                .with(DestroyOutOfBounds);
        }

        *translation.0.x_mut() += time.delta_seconds * delta_x * 100.0;
        *translation.0.y_mut() += time.delta_seconds * delta_y * 100.0;
    }
}

fn movement(time: Res<Time>, mut query: Query<(&Velocity, &mut Translation)>) {
    for (velocity, mut translation) in &mut query.iter() {
        *translation.0.x_mut() += time.delta_seconds * velocity.0.x();
        *translation.0.y_mut() += time.delta_seconds * velocity.0.y();
    }
}

fn destroy_out_of_bounds(
    mut commands: Commands,
    windows: Res<Windows>,
    mut query: Query<(&DestroyOutOfBounds, Entity, &mut Translation)>,
) {
    let window = windows.get_primary().unwrap();

    let x_min = -(window.width as f32 / 2.);
    let x_max = window.width as f32 / 2.;

    let y_max = window.height as f32 / 2.;
    let y_min = -(window.height as f32 / 2.);

    for (_, entity, mut translation) in &mut query.iter() {
        if translation.0.x() < x_min
            || translation.0.y() < y_min
            || translation.x() > x_max
            || translation.y() > y_max
        {
            println!("DESTROY ENTITY");
            commands.despawn(entity);
        }
    }
}

fn main() {
    App::build()
        .add_default_plugins()
        .add_resource(ClearColor(Color::rgb(0.7, 0.7, 0.1)))
        .add_startup_system(setup.system())
        .add_system(input.system())
        .add_system(movement.system())
        .add_system(destroy_out_of_bounds.system())
        .run();
}

[cart]

Yeah this makes sense to me. Im pretty sure the problem here is the array metadata for gpu-mapped components getting out of sync with the entities. I think we arent handling entity removal correctly in that part of the code.

I'll look into this. Despawning is important :smile:

[mcpar-land]

I've encountered this as well. Here's code that reproduces the issue.

use bevy::prelude::*;

struct DecayerTimer(Timer);

struct Decayer(f32);

fn decayer_system(
  mut commands: Commands,
  time: Res<Time>,
  mut timer: ResMut<DecayerTimer>,
  mut query: Query<(Entity, &mut Decayer)>,
) {
  timer.0.tick(time.delta_seconds);
  if timer.0.finished {
    commands
      .spawn_as_entity(
        Entity::new(),
        SpriteComponents {
          sprite: Sprite {
            size: Vec2::new(50.0, 50.0),
          },
          ..Default::default()
        },
      )
      .with(Decayer(2.0));
    timer.0.reset();
    println!("Spawned a decayer");
  }
  for (entity, mut decayer) in &mut query.iter() {
    decayer.0 -= time.delta_seconds;
    if decayer.0 <= 0.0 {
      commands.despawn(entity);
      println!("Deleted decayer: {:?}", entity);
    }
  }
}

fn init(mut commands: Commands) {
  commands.spawn(Camera2dComponents::default());
}

fn main() {
  App::build()
    .add_default_plugins()
    .add_resource(DecayerTimer(Timer::from_seconds(0.25)))
    .add_startup_system(init.system())
    .add_system(decayer_system.system())
    .run();
}

[DGriffin91]

I'm also getting this error when trying to despawn cubes in a system:
thread 'main' panicked at 'no empty slots available in array' [...]render_graph\nodes\render_resources_node.rs:50:17

It despawns the first one fine, then crashes. In my example I am spawning a cube every second and then despawning them when they move to a specific point. Do I need to free any render resources?

I put together a fairly minimal example here as a gist:
https://gist.github.com/DGriffin91/b592d4ce3ca8ea99204c9ba9a057b74c

[ashneverdawn]

I have this issue too. Whenever I change ui screens, I try to despawn the previous entities, but it causes the no empty slots available in array panic.

[hollg]

I'm seeing this issue too. My game spawns objects at the top of the screen and despawns them when they fall to the bottom. These two systems spawn and despawn them:

```rust
fn asteroid_creator_system(
mut commands: Commands,
mut materials: ResMut>,
time: Res,
mut timer: ResMut,
) {
let mut rng = rand::thread_rng();
timer.0.tick(time.delta_seconds);

if timer.0.finished {
    println!("spawn asteroid");
    commands
        .spawn(SpriteComponents {
            material: materials.add(Color::rgb(0.2, 0.2, 0.8).into()),
            translation: Translation(Vec3::new(rng.gen_range(-400.0, 400.0), 400.0, 0.0)),
            sprite: Sprite {
                size: Vec2::new(30.0, 30.0),
            },
            ..Default::default()
        })
        .with(Asteroid)
        .with(Gravity);
    timer.0.reset();
}

}

fn asteroid_destroyer_system(
mut commands: Commands,
mut query: Query<(&Asteroid, &mut Translation, Entity)>,
) {
for (_asteroid, translation, entity) in &mut query.iter() {
if translation.0.y() < -400.0 {
commands.despawn(entity);
}
}
}

[ashneverdawn]

There is a pr for a fix that worked for me. It hasn't been merged yet, but you can use it by putting this in your cargo.toml
bevy = { git = "https://github.com/Bobox214/bevy.git", branch = "fix_134_135" }
Hopefully it will get merged soon.