Atmosphere occlusion and PBR shading

[mate-h]

Objective

• Occlude the directional lights by the atmosphere
• More Physically accurate light values reaching the objects from directional lights
• Support volumetric shadowing through the atmosphere with an additional layer of FogVolume
• Strategic direction: use the FogVolume and expand on that implementation for shadow sampling Since it already uses pipeline specialization.
• For now keep the atmosphere pipeline as is, free from shadow sampling code since these effects only matter at large scales. Shadow sampling for the atmosphere can be implemented in a later PR for planetary rings, objects in space, other large scale objects.

Solution

• Bind the transmittance LUT to the core 3d mesh PBR shader
• tint the incoming light L to point P by the transmittance through the atmospheric medium
• Apply the same effects to volumetric fog
• Ensured that new new Atmosphere pipeline key works with deferred rendering
• Updated example to include water plane and screen space reflections. Removed the water plane from the GLB terrain asset. (small asset churn!)

Testing

cargo run --example atmosphere
# or
cargo run --example atmosphere --features=free_camera

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[ecoskey]

Looks great! Sorry I didn't review earlier, I've been pretty busy :)

[alice-i-cecile]

Missing release notes still ;) Perils of making pretty features.

Once there's at least a stub though, ping me and I'll merge!

[mate-h]

Ah fair! I missed those, will publish the release notes. Thanks 😊

[mate-h]

Taking a look at why the merge is failing!
Seems like its the run-examples-on-wasm I will make sure to test on wasm. I think maybe the SSR + deferred may have broke the warm build for the example.

[alice-i-cecile]

Yep, looks like WASM builds are properly broken with this :) Let me know when you have a fix!

[mate-h]

@alice-i-cecile Thanks for working with me on merging this PR! <3
The commit I pushed fixes the webGL2 examples since the atmosphere plugin is disabled in those cases. So I marked the resource query as optional in the arguments of the system function in the mesh view bindings file.

Unrelated problem to the CI being blocked, but ran into it while testing:
The atmosphere example is broken on webgpu on the main branch so I created an issue to track the fix:
#21700

I ran the CI tests locally and it's passing so it's likely just broken in github actions.