Atmosphere generated environment map lighting

[mate-h]

Objective

• Add generated environment lighting to the atmosphere for reflections and diffuse
• Tracking issue: Atmosphere PBR support and volumetric shadows tracking issue #20374

Solution

• created a new atmosphere node type called environment
• up-sampling the existing sky-view lookup texture and tied to the current view only. this atmosphere cube map pass has negligible performance impact, however the filtering pipeline does have a small performance impact to the example.
• using the new filtering pipeline, creates mip chain for different roughness levels as well as diffuse

Testing

• ran the atmosphere example

---

Showcase

commands.spawn((
    Camera3d::default(),
    // ...
    // Renders the atmosphere to the environment map from the perspective of the camera
    AtmosphereEnvironmentMapLight::default(),
));

Limitations, out of scope

• The generation does not support light probes (yet). This allows to render the atmosphere as a light probe from any "location" within the scene and within the overall atmosphere.
• therefore we assume that the relative scale of the scene to the atmosphere are orders of magnitude different , this is a safe assumption now with the current impl not officially supporting space views, yet
• the PBR directional light is still unaffected by the atmosphere (not tinted by it) out of scope for this PR
• unrelated issue to this PR: small black pixels around the fully reflective sphere. narrowed it down, this is a problem in the inscattering calculation based on the depth value in the render sky shader. however the addition of the env map light makes this problem more "apparent". to be addressed separately.
• past work staged for further PRs, up next: WIP: Atmosphere PBR support mate-h/bevy#10

[github-actions]

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[atlv24]

sweet! thanks for splitting it up :)

[JMS55]

I think user-facing docs need some work still. They focus too much on technical details (renders a cubemap), rather than what they're useful for (getting the atmosphere to contribute lighting).

Code looks good though.

[ecoskey]

Shaders look great! Just a couple nits for stuff on the rust side, but nothing blocking :)

[ecoskey]

this system should match prepare_atmosphere_probe_pipelines naming-scheme wise, and be in the same set

[mate-h]

This makes sense but should this be the other way around? i see auto exposure also uses the Queue render set, and queue_ naming prefix. but it's a view specific pipeline. I almost think I should match my naming to this since the entity we are considering in this case for queueing is the view / camera.

[ecoskey]

As long as they match I don't mind tbh

[mate-h]

Thanks for everyone’s feedback! I have addressed every comment, let me know if this version still needs any fine tuning. It is ready for a final review!

[ecoskey]

Suggested change

.after(init_atmosphere_probe_layout),

This is redundant

[Igor-dvr]

@mate-h It seems this comment was missed. Is this line redundant or we decided to leave it?

[mate-h]

I think in previous versions I was getting a runtime error without explicitly ordering systems, but with the queue render set changes it is probably safe to remove it! I have not had a chance to test without this line. Feel free to raise a PR if you do so! Thanks.

[JMS55]

@mate-h needs release notes, no?

[mate-h]

I am not at home right now, but i can do it as a follow up tomorrow! The release note is super simple though. Just added this new component no breaking changes to the atmosphere.

[JMS55]

Yeah, but we should highlight it in the blog post :)