Updating a spawned mesh asset requires RenderAssetUsages::default() in 0.16.0-rc.5

[oliver-dew]

Bevy version

0.16.0-rc.5

[Optional] Relevant system information

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

• Rust 1.85.1
• SystemInfo { os: "Linux (Ubuntu 24.04)", kernel: "6.11.0-21-generic", cpu: "AMD Ryzen 7 5825U with Radeon Graphics", core_count: "8", memory: "28.3 GiB" }

If your bug is rendering-related, copy the adapter info that appears when you run Bevy.

AdapterInfo { name: "AMD Radeon Graphics (RADV RENOIR)", vendor: 4098, device: 5607, device_type: IntegratedGpu, driver: "radv", driver_info: "Mesa 24.2.8-1ubuntu1~24.04.1", backend: Vulkan }

What you did

I have a mesh generated procedurally on the CPU, that has been spawned, perhaps several instances. I want to update/ replace the mesh (again procedurally on the CPU), by calling meshes.insert(handle, new_mesh). In 0.16, this only works if I set RenderAssetUsages::default() on the mesh asset. If instead I use RenderAssetUsages::RENDER_WORLD, spawned meshes update sporadically, after a few minutes.

MWE:

use bevy::{
    asset::RenderAssetUsages,
    input::keyboard::KeyboardInput,
    prelude::*,
    render::mesh::{Indices, PrimitiveTopology},
};
use rand::Rng;

fn main() {
    App::new()
        .add_plugins(DefaultPlugins)
        .add_systems(Startup, spawn_scene)
        .add_systems(Update, update_mesh_asset.run_if(on_event::<KeyboardInput>))
        .run();
}

fn spawn_scene(
    mut commands: Commands,
    mut meshes: ResMut<Assets<Mesh>>,
    mut materials: ResMut<Assets<StandardMaterial>>,
) {
    commands.spawn((
        Camera3d::default(),
        Transform::from_xyz(2.0, 2.0, 4.0).looking_at(Vec3::ZERO, Vec3::Y),
    ));

    let mesh = meshes.add(create_cube_mesh(Vec3::ONE));
    commands.spawn((
        Mesh3d(mesh),
        MeshMaterial3d(materials.add(StandardMaterial::default())),
    ));
}

// Press any key to update the mesh
fn update_mesh_asset(
    keys: Res<ButtonInput<KeyCode>>,
    mut meshes: ResMut<Assets<Mesh>>,
    query: Query<&Mesh3d>,
) {
    if keys.get_just_pressed().next().is_none() {
        return;
    };
    let Ok(mesh) = query.get_single() else { return };
    let handle = mesh.id();//0.clone();
    let mut rng = rand::rng();
    let cube = create_cube_mesh(Vec3::new(
        rng.random_range(0.5..1.5),
        rng.random_range(0.5..1.5),
        rng.random_range(0.5..1.5),
    ));
    meshes.insert(handle, cube);
}

fn create_cube_mesh(size: Vec3) -> Mesh {
    // Prior to 0.16, `RenderAssetUsages::RENDER_WORLD` works for every key press
    // In 0.16.0-rc.5, you need to use `RenderAssetUsages::default()`
    let mut mesh = Mesh::new(
        PrimitiveTopology::TriangleList,
        RenderAssetUsages::RENDER_WORLD,
    );
    mesh.insert_attribute(
        Mesh::ATTRIBUTE_POSITION,
        vec![
            // top (facing towards +y)
            [-0.5, 0.5, -0.5], // vertex with index 0
            [0.5, 0.5, -0.5],  // vertex with index 1
            [0.5, 0.5, 0.5],   // etc. until 23
            [-0.5, 0.5, 0.5],
            // bottom   (-y)
            [-0.5, -0.5, -0.5],
            [0.5, -0.5, -0.5],
            [0.5, -0.5, 0.5],
            [-0.5, -0.5, 0.5],
            // right    (+x)
            [0.5, -0.5, -0.5],
            [0.5, -0.5, 0.5],
            [0.5, 0.5, 0.5], // This vertex is at the same position as vertex with index 2, but they'll have different UV and normal
            [0.5, 0.5, -0.5],
            // left     (-x)
            [-0.5, -0.5, -0.5],
            [-0.5, -0.5, 0.5],
            [-0.5, 0.5, 0.5],
            [-0.5, 0.5, -0.5],
            // back     (+z)
            [-0.5, -0.5, 0.5],
            [-0.5, 0.5, 0.5],
            [0.5, 0.5, 0.5],
            [0.5, -0.5, 0.5],
            // forward  (-z)
            [-0.5, -0.5, -0.5],
            [-0.5, 0.5, -0.5],
            [0.5, 0.5, -0.5],
            [0.5, -0.5, -0.5],
        ]
        .iter()
        .map(|v| [v[0] * size.x, v[1] * size.y, v[2] * size.z])
        .collect::<Vec<[f32; 3]>>(),
    );
    mesh.insert_attribute(
        Mesh::ATTRIBUTE_UV_0,
        vec![
            // Assigning the UV coords for the top side.
            [0.0, 0.2],
            [0.0, 0.0],
            [1.0, 0.0],
            [1.0, 0.2],
            // Assigning the UV coords for the bottom side.
            [0.0, 0.45],
            [0.0, 0.25],
            [1.0, 0.25],
            [1.0, 0.45],
            // Assigning the UV coords for the right side.
            [1.0, 0.45],
            [0.0, 0.45],
            [0.0, 0.2],
            [1.0, 0.2],
            // Assigning the UV coords for the left side.
            [1.0, 0.45],
            [0.0, 0.45],
            [0.0, 0.2],
            [1.0, 0.2],
            // Assigning the UV coords for the back side.
            [0.0, 0.45],
            [0.0, 0.2],
            [1.0, 0.2],
            [1.0, 0.45],
            // Assigning the UV coords for the forward side.
            [0.0, 0.45],
            [0.0, 0.2],
            [1.0, 0.2],
            [1.0, 0.45],
        ],
    );
    mesh.insert_attribute(
        Mesh::ATTRIBUTE_NORMAL,
        vec![
            // Normals for the top side (towards +y)
            [0.0, 1.0, 0.0],
            [0.0, 1.0, 0.0],
            [0.0, 1.0, 0.0],
            [0.0, 1.0, 0.0],
            // Normals for the bottom side (towards -y)
            [0.0, -1.0, 0.0],
            [0.0, -1.0, 0.0],
            [0.0, -1.0, 0.0],
            [0.0, -1.0, 0.0],
            // Normals for the right side (towards +x)
            [1.0, 0.0, 0.0],
            [1.0, 0.0, 0.0],
            [1.0, 0.0, 0.0],
            [1.0, 0.0, 0.0],
            // Normals for the left side (towards -x)
            [-1.0, 0.0, 0.0],
            [-1.0, 0.0, 0.0],
            [-1.0, 0.0, 0.0],
            [-1.0, 0.0, 0.0],
            // Normals for the back side (towards +z)
            [0.0, 0.0, 1.0],
            [0.0, 0.0, 1.0],
            [0.0, 0.0, 1.0],
            [0.0, 0.0, 1.0],
            // Normals for the forward side (towards -z)
            [0.0, 0.0, -1.0],
            [0.0, 0.0, -1.0],
            [0.0, 0.0, -1.0],
            [0.0, 0.0, -1.0],
        ],
    );
    mesh.insert_indices(Indices::U32(vec![
        0, 3, 1, 1, 3, 2, // triangles making up the top (+y) facing side.
        4, 5, 7, 5, 6, 7, // bottom (-y)
        8, 11, 9, 9, 11, 10, // right (+x)
        12, 13, 15, 13, 14, 15, // left (-x)
        16, 19, 17, 17, 19, 18, // back (+z)
        20, 21, 23, 21, 22, 23, // forward (-z)
    ]));
    mesh
}

What went wrong

If it's not clear, break this out into:

• what were you expecting?
  In 0.16 I expect to be able to update a spawned mesh that has the usage RenderAssetUsages::RENDER_WORLD , as was possible prior to 0.16
• what actually happened?
  The asset updates, but only sporadically, after a few minutes. To get the old behaviour back, I need to set RenderAssetUsages::default() on the mesh asset

[hukasu]

there was an pr that made it so some render assets be unloaded from Assets after they were extracted to the render world when they have RenderAssetUsage::RENDER_WORLD, and it's been some time already, so to my understanding, Assets should return None when trying to fetch an asset that is RenderAssetUsage::RENDER_WORLD IIRC

[hukasu]

oh, you are not using get_mut you are completely replacing the mesh, i don't know what should be the behavior when doing this