bevyengine/bevy

bevy_solari

Experimental ray-traced lighting. Adds dynamic global illumination using GPU ray tracing (DXR / RTX / Vulkan ray query) on top of Bevy's PBR pipeline.

Purpose

bevy_solari is the engine's first foray into hardware ray tracing. It augments — not replaces — the existing PBR pipeline with:

A bottom-level acceleration structure (BLAS) per mesh.
A top-level acceleration structure (TLAS) per frame.
Ray-traced direct lighting.
Real-time GI via reservoir sampling (ReSTIR-like).
Denoising for the noisy ray-traced output.

The crate is gated behind the bevy_solari cargo feature and behind a runtime check that the GPU adapter supports ray tracing. Without that, falling back to the standard PBR path is the default.

Directory layout

crates/bevy_solari/src/
├── lib.rs                   # SolariPlugin
├── scene/                   # BLAS/TLAS construction
├── realtime/                # Reservoir sampling, temporal accumulation
├── pathtracer/              # Reference path tracer (validation, not real-time)
├── direct_light_sampling/
├── shaders/                 # WGSL ray-tracing shaders
└── …

Key abstractions

Type	File	Description
`SolariPlugin`	`crates/bevy_solari/src/lib.rs`	Adds the ray-tracing infrastructure.
`SolariLighting`	`crates/bevy_solari/src/realtime/`	Per-camera component opting into RT lighting.
`Pathtracer`	`crates/bevy_solari/src/pathtracer/`	Reference path tracer for validation.

How it works

graph LR
    Meshes -->|build| BLAS
    BLAS -->|aggregate| TLAS
    TLAS -->|trace| Rays[Ray-traced lighting]
    Rays -->|accumulate| Reservoir[ReSTIR reservoirs]
    Reservoir -->|denoise| Output
    Output -->|combine| PBR[PBR shader]

Each frame, BLASes for newly-meshed entities are constructed (or cached) and a TLAS is built from the active scene. Ray-traced direct lighting samples each light source via reservoir resampling. GI is approximated through the same machinery extended with secondary bounces.

A "reference" path tracer in pathtracer/ runs at much lower frame rate but produces an unbiased ground truth for comparing the real-time output.

Integration points

Depends on: bevy_render, bevy_pbr, bevy_camera, bevy_light, bevy_mesh, bevy_image, wgpu (with ray-tracing extensions).
Depended on by: Opt-in only.

Entry points for modification

Sampling improvements: realtime/. Reservoir code.
Denoiser: the relevant subdirectory; the denoiser has changed significantly across releases.
New light contribution: direct_light_sampling/.
The crate is experimental — APIs and shader code change rapidly.