Ability to extract any number of cameras

[Azorlogh]

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

I have a use case with an unlimited number of cameras per frame rendering to different targets.
Before PR #3635, I stored an ID in their name to identify these cameras and extract them.
Right now it seems the extract phase puts active cameras in resources, therefore I can only extract 1 camera per frame.

What solution would you like?

A way to extract any number of cameras at once in a system.
It would be neat to be able to store data in the marker component (I don't know if the name marker would still make sense though).

What alternative(s) have you considered?

I've considered moving a single camera around a bunch of times during rendering, but this means I have to keep track of all the render targets, and also since the cameras are attached their parent's transforms I'd have to keep track of that as well.

[Azorlogh]

As a workaround it's possible to manually extract the cameras' render phases and add the necessary components as per this system:

bevy/crates/bevy_render/src/camera/camera.rs

Line 288 in bf6de89

pub fn extract_cameras<M: Component + Default>(

[Azorlogh]

This is obsolete since the new camera-driven rendering I believe 👍