Extended materials not applying when spawned off camera or when visibility settings change.

[secretlyagoblin]

I've updated this post to be a bit more specific:

I have a system that searches for entities with a specific flag on them, and then replaces the material they have with an extended material, simplified in this example to the following implementation and shader (for the purposes of this example the shader just turns the object pink):

@fragment
fn fragment(
) -> @location(0) vec4<f32> {    
    return vec4<f32>(1.0, 0.4, 0.7, 1.0);
}

and

impl MaterialExtension for DisplacementMaterialExtension {
    fn fragment_shader() -> ShaderRef {
        SHADER_ASSET_PATH.into()
    }
}

When I update the material on these objects:

commands.insert_batch(
    entities
        .iter()
        .map(|(entity, _, _)| {(
                *entity,
                MeshMaterial3d(displacement_material_handle.clone()))
        })
        .collect());

It only applies to objects within the view frustum of the camera:

2025-07-16.09-33-27.mp4

Not only that, if I change the visibility of the root object they all inherent their visibility from, when they are made visible again, the extended shader is no longer working on any of them:

2025-07-17.10-41-08.mp4

Does anybody have any idea why this might be occuring?

[IceSentry]

This issue still occurs if I disable frustum culling on the entities in question.

My only guess would have been with this, but if that didn't work I feel it has to be something in your shader. That's the only thing I can think of that would be in the hands of bevy itself.

Also, I'm a bit confused what you mean when you say things like "walking towards the camera". Isn't the camera pointing in the movement direction?

[secretlyagoblin]

Hello, thanks for your reply - I've put a video of the effect in a comment below. Just to try and isolate and disprove the shader being the issue, I've changed by shader to be:

@fragment
fn fragment(
) -> @location(0) vec4<f32> {    
    return vec4<f32>(1.0, 0.4, 0.7, 1.0);
}

and my custom material to be

impl MaterialExtension for DisplacementMaterialExtension {
    fn fragment_shader() -> ShaderRef {
        SHADER_ASSET_PATH.into()
    }
}

and I'm getting the exact same result - if I zoom the camera in on my character and regenerate the cells, any object that is behind the camera at the frame it is given an extended material doesn't get the extended material properties applied.

2025-07-16.09-33-27.mp4

[secretlyagoblin]

I've updated the original question to be clearer.

[secretlyagoblin]

I've woken up with a clearer head and I've made a short video - when I hit space, I can flush every chunk and force it to respawn. I added a fragment shader that colours everything pink to test my logic, and you can see that the material isn't being applied to anything that spawns behind the camera.

2025-07-16.08-34-43.mp4

[secretlyagoblin]

I've added this as a bevy bug because I've observed the same behaviour if you edit the vanilla extended material examples:

#20168