Reduce aliasing and Moiré patterns in temporal shadow filtering

[superdump]

Objective

• Reduce aliasing and Moiré patterns in temporal shadow filtering

Solution

• Use interleaved gradient noise based on screen UV not light local UV

NOTE: It only affects ShadowFilteringMethod::Temporal or non-temporal PCSS

Testing

Tested with pcss and shadow_biases examples. The latter was more useful - see showcase section.

NOTE: It only affects ShadowFilteringMethod::Temporal or non-temporal PCSS

However, this touches more code paths and all combinations need testing:

• Light types:
  • Point
  • Spot
  • Directional
• Shadow mapping
• Soft shadows (PCSS)
• Transmission
• Distance fog

---

Showcase

main:

PR:

It also makes the full temporal mode where the noise patterns change each frame look much better, especially with TAA enabled. That is however a bit difficult to illustrate due to the animation aspect.

[github-actions]

Your PR caused a change in the graphical output of an example or rendering test. This might be intentional, but it could also mean that something broke!
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If it's expected, please add the M-Deliberate-Rendering-Change label.

If this change seems unrelated to your PR, you can consider updating your PR to target the latest main branch, either by rebasing or merging main into it.

[JMS55]

LGTM! Might need a migration guide though? I'm not sure about our policy for shader stuff like this, where the general advice is "copy and re-apply your changes each time you update bevy".

[pcwalton]

Historically we haven't really included shader guts in the migration guides. naga_oil doesn't have privacy really, so technically every change to any function anywhere is a breaking change, which would be too aggressive of a policy. Maybe with WESL we can start marking functions as private, which would let us come up with a migration guide policy for shader functions?

[JMS55]

Generally I agree, e.g. it makes no sense to have migrations for random SSR functions or whatever, but specifically for our material/lighting code, a lot of people copy paste or import that.

[mockersf]

This PR broke examples atmospheric_fog and color_grading and a few others