Panic upon using a `CameraProjection` with `DirectionalLight` shadows

[doonv]

Bevy version

main (f84672b)

Relevant system information

If you cannot get Bevy to build or run on your machine, please include:

• Rust: Stable + Nightly (Crashes on both)
• Kubuntu 23.10

AdapterInfo { name: "NVIDIA GeForce RTX 3060", vendor: 4318, device: 9540, device_type: DiscreteGpu, driver: "NVIDIA", driver_info: "535.154.05", backend: Vulkan }

What you did

I wanted to use a custom CameraProjection.

use bevy::prelude::*;
use bevy::{
    core_pipeline::{
        core_3d::graph::SubGraph3d,
        tonemapping::{DebandDither, Tonemapping},
    },
    render::{
        camera::{CameraMainTextureUsages, CameraRenderGraph},
        primitives::Frustum,
        view::{ColorGrading, VisibleEntities},
    },
};

fn main() {
    App::new()
        .add_plugins(DefaultPlugins)
        .add_systems(Startup, setup)
        .run();
}

fn setup(mut commands: Commands) {
    commands.spawn(DirectionalLightBundle {
        directional_light: DirectionalLight {
            shadows_enabled: true, // This is required for it to panic, I don't know why
            ..default()
        },
        ..default()
    });
    
    // This is identical to `Camera3dBundle` except for the projection
    commands.spawn((
        Camera::default(),
        CameraRenderGraph::new(SubGraph3d),
        PerspectiveProjection {
            aspect_ratio: 1.0,
            fov: 90.0,
            near: 1.0,
            far: 1000.0,
        },
        VisibleEntities::default(),
        Frustum::default(),
        Transform::default(),
        GlobalTransform::default(),
        Camera3d::default(),
        Tonemapping::default(),
        DebandDither::Enabled,
        ColorGrading::default(),
        CameraMainTextureUsages::default(),
    ));
}

What went wrong

It turns out using a CameraProjection component directly on the camera instead of using it through Projection causes a panic. It even panics with built-in projections like PerspectiveProjection.

2024-02-09T21:40:51.187168Z  INFO bevy_winit::system: Creating new window "App" (0v1)
2024-02-09T21:40:51.187435Z  INFO log: Guessed window scale factor: 1    
2024-02-09T21:40:51.362996Z  INFO bevy_render::renderer: AdapterInfo { name: "NVIDIA GeForce RTX 3060", vendor: 4318, device: 9540, device_type: DiscreteGpu, driver: "NVIDIA", driver_info: "535.154.05", backend: Vulkan }
2024-02-09T21:40:51.875860Z  INFO bevy_diagnostic::system_information_diagnostics_plugin::internal: SystemInfo { os: "Linux 23.10 Ubuntu", kernel: "6.5.0-17-generic", cpu: "", core_count: "10", memory: "15.4 GiB" }
thread 'Compute Task Pool (1)' panicked at crates/bevy_pbr/src/render/light.rs:1139:18:
called `Option::unwrap()` on a `None` value
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
Encountered a panic in system `bevy_pbr::render::light::prepare_lights`!
thread 'main' panicked at crates/bevy_render/src/pipelined_rendering.rs:49:67:
called `Result::unwrap()` on an `Err` value: RecvError

[rparrett]

// This is identical to `Camera3dBundle` except for the projection

That's not true -- Camera3dBundle includes a Perspective component, not a PerspectiveProjection.

You probably want

Projection::from(PerspectiveProjection {
    aspect_ratio: 1.0,
    fov: 90.0,
    near: 1.0,
    far: 1000.0,
}),

instead.

[doonv]

Camera3dBundle includes a Perspective component, not a PerspectiveProjection.

That's what I meant by saying "except for the projection"

[rparrett]

Oops, major misunderstanding on my part.

[doonv]

I have found the bug, here:

bevy/crates/bevy_pbr/src/lib.rs

Line 300 in 0031391

build_directional_light_cascades::<Projection>,

If build_directional_light_cascades<T> is not added for the projection you are using, bevy will crash. And it's only added for Projection. Adding build_directional_light_cascades::<PerspectiveProjection> fixes this.

I am currently working on a PR to fix this, not only for Bevy's projections. But all projections.