Migrate pcss example to use FeathersRadio

[kfc35]

Objective

• Part of UI Migration Plan for Bevy Examples #24112 , Phase 4. Kick it off a tiny bit to make it easier for others to get involved. I figured it would be more strategic for me to break down the more complex work and leave some of the easier bits for later if people who want to get acquainted with Bevy dev.

Solution

• Add some new helpers that will take over the prior option button logic. Reviewers should probably read radio.rs first.
• Remove any need to listen to messages by just making adding the value as a component on the radio buttons. It will be used to set the value of relevant settings.
• Note that pcss now uses bsn! to spawn the buttons only, so the example has a mix of regular spawns and spawn scenes.

Once this is merged, phase 4 is unblocked to use these new methods for converting the other examples mentioned.

Testing

• cargo run --example pcss --features="experimental_pbr_pcss,bevy_feathers”

---

Showcase

Before and After

Before:

After:
https://github.com/user-attachments/assets/c8713ce4-b852-4fca-a62e-100f8c8ba16a

[viridia]

Amazing work!

[kristoff3r]

I tried running the example but on this branch it consistently panics deep inside the renderer, which doesn't happen on main. I have no idea how your changes could cause this though.

$ cargo run --example pcss --features="experimental_pbr_pcss,bevy_feathers,debug"

2026-07-13T14:35:25.805292Z  INFO bevy_diagnostic::system_information_diagnostics_plugin::internal: SystemInfo { os: "Linux (NixOS 26.05)", kernel: "6.18.37", cpu: "AMD Ryzen 7 5800X 8-Core Processor", core_count: "8", memory: "47.0 GiB" }
2026-07-13T14:35:25.912158Z  INFO bevy_render::renderer: AdapterInfo { name: "NVIDIA GeForce RTX 3070", vendor: 4318, device: 9352, device_type: DiscreteGpu, device_pci_bus_id: "0000:0a:00.0", driver: "NVIDIA", driver_info: "595.71.05", backend: Vulkan, subgroup_min_size: 32, subgroup_max_size: 32, transient_saves_memory: false }

[...]

thread 'main' (313907) panicked at crates/bevy_render/src/render_phase/mod.rs:308:9:
assertion `left == right` failed
  left: 2
 right: 1
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

thread 'Compute Task Pool (3)' (313921) panicked at crates/bevy_render/src/render_phase/mod.rs:308:9:
assertion `left == right` failed
  left: 2
 right: 1

thread 'Compute Task Pool (2)' (313920) panicked at crates/bevy_render/src/render_phase/mod.rs:308:9:
assertion `left == right` failed
  left: 2
 right: 1

thread 'main' (313907) panicked at crates/bevy_ecs/src/error/handler.rs:141:1:
Encountered an error in system `bevy_pbr::render::light::queue_shadows`: System panicked


thread 'Compute Task Pool (2)' (313920) panicked at crates/bevy_ecs/src/error/handler.rs:141:1:
Encountered an error in system `bevy_pbr::material::queue_material_meshes`: System panicked

Encountered a panic in system `bevy_pbr::render::light::queue_shadows
thread 'Compute Task Pool (3)' (313921) panicked at crates/bevy_ecs/src/error/handler.rs:141:1:
Encountered an error in system `bevy_pbr::prepass::queue_prepass_material_meshes`: System panicked

`!
Encountered a panic in system `bevy_pbr::material::queue_material_meshes`!
Encountered a panic in system `bevy_pbr::prepass::queue_prepass_material_meshes`!

thread 'Render thread' (313956) panicked at crates/bevy_ecs/src/error/handler.rs:141:1:
Encountered an error in system `bevy_render::run_render_schedule`: Exclusive system panicked

Encountered a panic in system `bevy_render::run_render_schedule`!

[kfc35]

I tried running the example but on this branch it consistently panics deep inside the renderer, which doesn't happen on main.

I encountered this last night and concluded that my changes are mostly unrelated to the panic. I can get the panic to happen on main when I switch the light type so I spun out #24973

However it did make me wonder a tiny bit why moving to feathers sometimes makes it panic by itself. I cant see obviously why the light type would change on initialization but ill see what I can figure out

[kfc35]

The panicking should be resolved by #24980