change the ribbon example into a tracer example.

[naasblod]

I think this could be more helpful for people wanting to use the ribbon example. In my mind "tracers" are the most used application for this sort of thing, If you feel it isn't just close it.

run with:
cargo run --example ribbon --features="bevy/bevy_winit bevy/bevy_pbr 3d bevy/bevy_gizmos"

[djeedai]

If I understand correctly you're proposing to replace the purely GPU driven motion with a property-based one, to show how a ribbon can follow a target as a kind of trail, is that it?

I don't have any objection, but if you feel that tracers are common (I don't have an opinion, probably that's correct) then I'd expand a tiny bit the top level documentation to mention that this example shows a "tracer" (so that if someone search that term they find that example) and explain how a property is used to link the particle position to some CPU position (as this is probably a common feature to want).

[naasblod]

Screen.Recording.2024-10-15.at.21.23.02.mov

[naasblod]

Is there anything else you'd like me to do with this or should I close it? Maybe move to a separate example?

[pcwalton]

This is fine by me. Note that the little gaps between ribbon segments are something I've been thinking about fixing with the singly linked list experiment (that needs #387 to land first).

[djeedai]

Apology @naasblod I had to prioritize merging the large fix from @pcwalton for ribbons due to its size and criticality, which now makes this change conflict. Please let me know if you have time ideally to fix, otherwise I'll try to find time to do it myself. Thanks for your understanding!

[naasblod]

No worries friend ❤️! I'll take care of it!

[naasblod]

I think that does it. Could use a final review

[djeedai]

@naasblod the example fails to build:

error[E0412]: cannot find type `Gizmos` in this scope
   --> examples\ribbon.rs:115:17
    |
115 |     mut gizmos: Gizmos,
    |                 ^^^^^^ not found in this scope

[naasblod]

@djeedai should be fixed now.
The example needed to be ran with bevy/bevy_gizmos but I removed the usage instead.

[djeedai]

@naasblod for next time, if you need a dependency for examples and tests only, you can add it to the [dev-dependencies] section in Cargo.toml.

[naasblod]

Ah! Thanks, that's useful to know!