Bloom not restricted to cameras with BloomSettings?

[rparrett]

Bevy version

• latest main
• bevy 0.9
• PR [Merged by Bors] - Revamp Bloom #6677 as of 1/27

Relevant system information

AdapterInfo { name: "Apple M1 Max", vendor: 0, device: 0, device_type: IntegratedGpu, driver: "", driver_info: "", backend: Metal }
SystemInfo { os: "MacOS 13.1 ", kernel: "22.2.0", cpu: "Apple M1 Max", core_count: "10", memory: "64.0 GiB" }

What you did

I want bloom to be applied only to a subset of my scene, so I added a separate camera with BloomSettings.

use bevy::{
    core_pipeline::{bloom::BloomSettings, clear_color::ClearColorConfig},
    prelude::*,
    render::view::RenderLayers,
    sprite::MaterialMesh2dBundle,
};

fn main() {
    App::new()
        .insert_resource(ClearColor(Color::rgb(0.1, 0.1, 0.1)))
        .add_plugins(DefaultPlugins)
        .add_startup_system(setup)
        .run();
}

fn setup(
    mut commands: Commands,
    mut meshes: ResMut<Assets<Mesh>>,
    mut materials: ResMut<Assets<ColorMaterial>>,
) {
    let no_bloom_layer = RenderLayers::layer(0);
    let bloom_layer = RenderLayers::layer(1);

    commands.spawn((
        Camera2dBundle {
            camera: Camera {
                hdr: true,
                ..default()
            },
            ..default()
        },
        no_bloom_layer,
    ));

    commands.spawn((
        Camera2dBundle {
            camera_2d: Camera2d {
                clear_color: ClearColorConfig::None,
                ..default()
            },
            camera: Camera {
                hdr: true,
                order: 1,
                ..default()
            },
            ..default()
        },
        bloom_layer,
        BloomSettings {
            threshold: 0.5,
            ..default()
        },
    ));

    let (saturation, lightness, alpha) = (0.8, 0.7, 1.0);

    // Circle
    commands.spawn((
        MaterialMesh2dBundle {
            mesh: meshes.add(shape::Circle::new(100.).into()).into(),
            material: materials.add(ColorMaterial::from(Color::Hsla {
                hue: 180.,
                saturation,
                lightness,
                alpha,
            })),
            transform: Transform::from_translation(Vec3::new(-125., 0., 0.)),
            ..default()
        },
        no_bloom_layer,
    ));

    // Hexagon
    commands.spawn((
        MaterialMesh2dBundle {
            mesh: meshes
                .add(shape::RegularPolygon::new(100., 6).into())
                .into(),
            material: materials.add(ColorMaterial::from(Color::Hsla {
                hue: 120.,
                saturation,
                lightness,
                alpha,
            })),
            transform: Transform::from_translation(Vec3::new(125., 0., 0.)),
            ..default()
        },
        bloom_layer,
    ));
}

What went wrong

BloomSettings is only on the camera that renders the hexagon, so I expected only the hexagon to get bloom.

Instead, both shapes get bloom.

Additional information

It's not clear if this is user error, a known limitation, or a bug.

[JMS55]

Reminder to myself to investigate this.

[Elabajaba]

Afaik the fix for this is to give each camera their own set of textures and then compositing them together after everything.

Ideally there'd be some system that would detect for each post processing effect if it's being run on all the views that are going to be composited together or not so you could run post processing after compositing if all views used a post-fx to avoid running the same post processing passes multiple times (which can be very expensive). However, his gets complicated very quickly due to certain effects having to run before others, and requires a better post-processing stack for creating and managing shaders.

This can also get quite expensive in terms of the VRAM and bandwidth cost of compositing all the different sets of textures together.