Solari: Denoiser motion vector metal compat

[mate-h]

Objective

• Solari support on metal backends #25123 introduced Solari on Metal
• Solari: Improved reflection denoising #25423 broke compatibility with Metal

It changed Solari’s motion vectors from a sampled texture_2d<f32> to texture_storage_2d<rg16float, read_write>.

Presently on main we get a crash on Metal:

2026-09-14T18:43:13.274411Z ERROR bevy_render::error_handler: Caught rendering error: Validation Error

Caused by:
  In Device::create_bind_group_layout, label = 'solari_lighting_bind_group_layout'
    Binding index 5: ReadWrite access to storage textures with format Rg16Float is not supported

rg16float can't be bound as a read-write storage texture on Metal. Vulkan and DX12 usually can.

Solution

ReSTIR only samples motion vectors to reproject last frame's reservoir. The only writer is DLSS Ray Reconstruction PSR, and only for perfect mirrors — everything else already goes to specular_motion_vectors.

At pipeline init we check whether the adapter supports STORAGE_READ_WRITE on rg16float. If it does, we keep the storage binding and write PSR motion in place. If not, we sample a texture_2d<f32> and skip the write. DLSS RR doesn't run on those GPUs anyway.

Testing

• Ran the Solari example on Metal (Apple M5), no crash
• Could not test the DLSS in-place path (no DLSS_SDK / NVIDIA GPU on this machine)
• CI check for Metal + Solari is still missing (no available hw to test on?)

[stuartparmenter]

Would like to land this in 0.20 so solari on metal isn't broken

[JMS55]

Lgtm but some nits