Propagation for RenderLayers

[Sigma-dev]

What problem does this solve or what need does it fill?

Visibility propagation is:

• The norm across software
• Intuitive
• Practical

Which is why we have it, and it's great.

But when you need something more complicated than global visibility, you end up using RenderLayers, and in my case being confused that they don't propagate.

This lack of propagation is in my opinion both unintuitive and impractical.

For example if you want to make a gltf model hidden from a specific camera, you now need to somehow insert the RenderLayers across the whole gltf tree.

What solution would you like?

My solution is to implement propagation very similar to the existing Visibility propagation.

So RenderLayers would probably become an enum like:

• Inherited
• Layers(layers)

What alternative(s) have you considered?

For my GLTF problem, I could do some iter_descendants stuff but it would be pretty clunky in my opinion.

Additional context

I'm up to implement this into a PR if the design is validated 👍

[alice-i-cecile]

Note that this already exists via https://docs.rs/bevy/latest/bevy/app/struct.HierarchyPropagatePlugin.html.

This issue would be a good place to discuss a) how can we make that more obvious in the docs and b) should this be on by default.