fix(pcss ex / light despawning): add shadow maps and extracted lights to SyncComponent for lights

[kfc35]

Objective

• Fixes Pcss example is broken #23769 , but I wonder if there should be more components added to the lights’ SyncComponents.

Solution

I git bisect’d the issue to bbcc1e6 which has to do with SyncComponents.
I noticed that some manual extraction of lights happens in bevy_pbr/src/render/light.rs. I figured that maybe more render components should be sync’d with the main world of component of lights. The behavior before that commit was that the render entity would be despawned and then recreated anew for syncing, so I think there’s something happening with lingering components on the render entity.

Adding the Extracted*Light components to each respective Light’s sync component only fixed it when toggling from DirectionalLight -> Another light. All other toggles were still broken.

After adding the ShadowMap components, the toggles are pretty much 99% fixed. The shadow can rarely disappear if switching between Spot and Point light very quickly in succession, but I haven’t had it happen in a while.

I suspect this fix is suboptimal because the shadow disappears and then comes back in when switching for the first time to the new light source, which doesn’t seem happen on the last good commit (b22e71f)? Might just be me.

I’ll also say that the example reuses the same main world entity for all 3 lights and toggles between the three (it removes all three light components on toggle and then adds one back). Part of me wonders if the example should also be restructured because of that / if this example might be broken because of this structuring. At the very least, this fix is not complete once #23790 is merged, so #23802 should be considered.

Testing

• You can toggle between the lights and the shadows stay mostly in tact except for the described scenario between spot and point: cargo run --example pcss --features=“experimental_pbr_pcss”