bevy_solari: RIS for Direct Lighting (#19620)

# Objective

- Start the realtime direct lighting work for bevy solari

## Solution

- Setup all the CPU-side code for the realtime lighting path (minus some
parts for the temporal reuse I haven't written yet)
- Implement RIS with 32 samples to choose a good random light
- Don't sample a disk for the directional light, just treat it as a
single point. This is faster and not much worse quality.

## Future
- Spatiotemporal reuse (ReSTIR DI)
- Denoiser (DLSS-RR)
- Light tile optimization for faster light selection 
- Indirect lighting (ReSTIR GI)

## Testing
- Run the solari example to see realtime
- Run the solari example with `-- --pathtracer` to see the existing
pathtracer

---

## Showcase

1 frame direct lighting:

![image](https://github.com/user-attachments/assets/b70b968d-9c73-4983-9b6b-b60cace9b47a)

Accumulated pathtracer output:

![image](https://github.com/user-attachments/assets/d681bded-ef53-4dbe-bcca-96997c58c3be)

---------

Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>

Cargo.toml

@@ -1284,9 +1284,9 @@ required-features = ["bevy_solari"]
 
 [package.metadata.example.solari]
 name = "Solari"
-description = "Demonstrates realtime dynamic global illumination rendering using Bevy Solari."
+description = "Demonstrates realtime dynamic raytraced lighting using Bevy Solari."
 category = "3D Rendering"
-wasm = false
+wasm = false                                                                        # Raytracing is not supported on the web
 
 [[example]]
 name = "spherical_area_lights"

crates/bevy_render/src/diagnostic/mod.rs

@@ -148,7 +148,7 @@ pub struct PassSpanGuard<'a, R: ?Sized, P> {
 }
 
 impl<R: RecordDiagnostics + ?Sized, P: Pass> PassSpanGuard<'_, R, P> {
-    /// End the span. You have to provide the same encoder which was used to begin the span.
+    /// End the span. You have to provide the same pass which was used to begin the span.
     pub fn end(self, pass: &mut P) {
         self.recorder.end_pass_span(pass);
         core::mem::forget(self);

crates/bevy_solari/Cargo.toml

@@ -15,6 +15,7 @@ bevy_asset = { path = "../bevy_asset", version = "0.17.0-dev" }
 bevy_color = { path = "../bevy_color", version = "0.17.0-dev" }
 bevy_core_pipeline = { path = "../bevy_core_pipeline", version = "0.17.0-dev" }
 bevy_derive = { path = "../bevy_derive", version = "0.17.0-dev" }
+bevy_diagnostic = { path = "../bevy_diagnostic", version = "0.17.0-dev" }
 bevy_ecs = { path = "../bevy_ecs", version = "0.17.0-dev" }
 bevy_math = { path = "../bevy_math", version = "0.17.0-dev" }
 bevy_mesh = { path = "../bevy_mesh", version = "0.17.0-dev" }
@@ -27,8 +28,9 @@ bevy_render = { path = "../bevy_render", version = "0.17.0-dev" }
 bevy_transform = { path = "../bevy_transform", version = "0.17.0-dev" }
 
 # other
-tracing = { version = "0.1", default-features = false, features = ["std"] }
+bytemuck = { version = "1" }
 derive_more = { version = "1", default-features = false, features = ["from"] }
+tracing = { version = "0.1", default-features = false, features = ["std"] }
 
 [lints]
 workspace = true

crates/bevy_solari/src/lib.rs

@@ -6,6 +6,7 @@
 //!
 //! ![`bevy_solari` logo](https://raw.githubusercontent.com/bevyengine/bevy/assets/branding/bevy_solari.svg)
 pub mod pathtracer;
+pub mod realtime;
 pub mod scene;
 
 /// The solari prelude.
@@ -13,28 +14,28 @@ pub mod scene;
 /// This includes the most common types in this crate, re-exported for your convenience.
 pub mod prelude {
     pub use super::SolariPlugin;
-    pub use crate::pathtracer::Pathtracer;
+    pub use crate::realtime::SolariLighting;
     pub use crate::scene::RaytracingMesh3d;
 }
 
+use crate::realtime::SolariLightingPlugin;
+use crate::scene::RaytracingScenePlugin;
 use bevy_app::{App, Plugin};
 use bevy_render::settings::WgpuFeatures;
-use pathtracer::PathtracingPlugin;
-use scene::RaytracingScenePlugin;
 
 /// An experimental plugin for raytraced lighting.
 ///
 /// This plugin provides:
-/// * (Coming soon) - Raytraced direct and indirect lighting.
+/// * [`SolariLightingPlugin`] - Raytraced direct and indirect lighting (indirect lighting not yet implemented).
 /// * [`RaytracingScenePlugin`] - BLAS building, resource and lighting binding.
-/// * [`PathtracingPlugin`] - A non-realtime pathtracer for validation purposes.
+/// * [`pathtracer::PathtracingPlugin`] - A non-realtime pathtracer for validation purposes.
 ///
 /// To get started, add `RaytracingMesh3d` and `MeshMaterial3d::<StandardMaterial>` to your entities.
 pub struct SolariPlugin;
 
 impl Plugin for SolariPlugin {
     fn build(&self, app: &mut App) {
-        app.add_plugins((RaytracingScenePlugin, PathtracingPlugin));
+        app.add_plugins((RaytracingScenePlugin, SolariLightingPlugin));
     }
 }
 

crates/bevy_solari/src/realtime/extract.rs

@@ -0,0 +1,27 @@
+use super::{prepare::SolariLightingResources, SolariLighting};
+use bevy_ecs::system::{Commands, ResMut};
+use bevy_pbr::deferred::SkipDeferredLighting;
+use bevy_render::{camera::Camera, sync_world::RenderEntity, MainWorld};
+
+pub fn extract_solari_lighting(mut main_world: ResMut<MainWorld>, mut commands: Commands) {
+    let mut cameras_3d = main_world.query::<(RenderEntity, &Camera, Option<&mut SolariLighting>)>();
+
+    for (entity, camera, mut solari_lighting) in cameras_3d.iter_mut(&mut main_world) {
+        let mut entity_commands = commands
+            .get_entity(entity)
+            .expect("Camera entity wasn't synced.");
+        if solari_lighting.is_some() && camera.is_active {
+            entity_commands.insert((
+                solari_lighting.as_deref().unwrap().clone(),
+                SkipDeferredLighting,
+            ));
+            solari_lighting.as_mut().unwrap().reset = false;
+        } else {
+            entity_commands.remove::<(
+                SolariLighting,
+                SolariLightingResources,
+                SkipDeferredLighting,
+            )>();
+        }
+    }
+}

crates/bevy_solari/src/realtime/mod.rs

@@ -0,0 +1,91 @@
+mod extract;
+mod node;
+mod prepare;
+
+use crate::SolariPlugin;
+use bevy_app::{App, Plugin};
+use bevy_asset::embedded_asset;
+use bevy_core_pipeline::{
+    core_3d::graph::{Core3d, Node3d},
+    prepass::{DeferredPrepass, DepthPrepass, MotionVectorPrepass},
+};
+use bevy_ecs::{component::Component, reflect::ReflectComponent, schedule::IntoScheduleConfigs};
+use bevy_pbr::DefaultOpaqueRendererMethod;
+use bevy_reflect::{std_traits::ReflectDefault, Reflect};
+use bevy_render::{
+    load_shader_library,
+    render_graph::{RenderGraphApp, ViewNodeRunner},
+    renderer::RenderDevice,
+    view::Hdr,
+    ExtractSchedule, Render, RenderApp, RenderSystems,
+};
+use extract::extract_solari_lighting;
+use node::SolariLightingNode;
+use prepare::prepare_solari_lighting_resources;
+use tracing::warn;
+
+pub struct SolariLightingPlugin;
+
+impl Plugin for SolariLightingPlugin {
+    fn build(&self, app: &mut App) {
+        embedded_asset!(app, "restir_di.wgsl");
+        load_shader_library!(app, "reservoir.wgsl");
+
+        app.register_type::<SolariLighting>()
+            .insert_resource(DefaultOpaqueRendererMethod::deferred());
+    }
+
+    fn finish(&self, app: &mut App) {
+        let render_app = app.sub_app_mut(RenderApp);
+
+        let render_device = render_app.world().resource::<RenderDevice>();
+        let features = render_device.features();
+        if !features.contains(SolariPlugin::required_wgpu_features()) {
+            warn!(
+                "SolariLightingPlugin not loaded. GPU lacks support for required features: {:?}.",
+                SolariPlugin::required_wgpu_features().difference(features)
+            );
+            return;
+        }
+        render_app
+            .add_systems(ExtractSchedule, extract_solari_lighting)
+            .add_systems(
+                Render,
+                prepare_solari_lighting_resources.in_set(RenderSystems::PrepareResources),
+            )
+            .add_render_graph_node::<ViewNodeRunner<SolariLightingNode>>(
+                Core3d,
+                node::graph::SolariLightingNode,
+            )
+            .add_render_graph_edges(
+                Core3d,
+                (Node3d::EndMainPass, node::graph::SolariLightingNode),
+            );
+    }
+}
+
+/// A component for a 3d camera entity to enable the Solari raytraced lighting system.
+///
+/// Must be used with `CameraMainTextureUsages::default().with(TextureUsages::STORAGE_BINDING)`, and
+/// `Msaa::Off`.
+#[derive(Component, Reflect, Clone)]
+#[reflect(Component, Default, Clone)]
+#[require(Hdr, DeferredPrepass, DepthPrepass, MotionVectorPrepass)]
+pub struct SolariLighting {
+    /// Set to true to delete the saved temporal history (past frames).
+    ///
+    /// Useful for preventing ghosting when the history is no longer
+    /// representative of the current frame, such as in sudden camera cuts.
+    ///
+    /// After setting this to true, it will automatically be toggled
+    /// back to false at the end of the frame.
+    pub reset: bool,
+}
+
+impl Default for SolariLighting {
+    fn default() -> Self {
+        Self {
+            reset: true, // No temporal history on the first frame
+        }
+    }
+}

crates/bevy_solari/src/realtime/node.rs

@@ -0,0 +1,200 @@
+use super::{prepare::SolariLightingResources, SolariLighting};
+use crate::scene::RaytracingSceneBindings;
+use bevy_asset::load_embedded_asset;
+use bevy_core_pipeline::prepass::ViewPrepassTextures;
+use bevy_diagnostic::FrameCount;
+use bevy_ecs::{
+    query::QueryItem,
+    world::{FromWorld, World},
+};
+use bevy_render::{
+    camera::ExtractedCamera,
+    diagnostic::RecordDiagnostics,
+    render_graph::{NodeRunError, RenderGraphContext, ViewNode},
+    render_resource::{
+        binding_types::{
+            storage_buffer_sized, texture_2d, texture_depth_2d, texture_storage_2d, uniform_buffer,
+        },
+        BindGroupEntries, BindGroupLayout, BindGroupLayoutEntries, CachedComputePipelineId,
+        ComputePassDescriptor, ComputePipelineDescriptor, PipelineCache, PushConstantRange,
+        ShaderStages, StorageTextureAccess, TextureSampleType,
+    },
+    renderer::{RenderContext, RenderDevice},
+    view::{ViewTarget, ViewUniform, ViewUniformOffset, ViewUniforms},
+};
+
+pub mod graph {
+    use bevy_render::render_graph::RenderLabel;
+
+    #[derive(Debug, Hash, PartialEq, Eq, Clone, RenderLabel)]
+    pub struct SolariLightingNode;
+}
+
+pub struct SolariLightingNode {
+    bind_group_layout: BindGroupLayout,
+    initial_and_temporal_pipeline: CachedComputePipelineId,
+    spatial_and_shade_pipeline: CachedComputePipelineId,
+}
+
+impl ViewNode for SolariLightingNode {
+    type ViewQuery = (
+        &'static SolariLighting,
+        &'static SolariLightingResources,
+        &'static ExtractedCamera,
+        &'static ViewTarget,
+        &'static ViewPrepassTextures,
+        &'static ViewUniformOffset,
+    );
+
+    fn run(
+        &self,
+        _graph: &mut RenderGraphContext,
+        render_context: &mut RenderContext,
+        (
+            solari_lighting,
+            solari_lighting_resources,
+            camera,
+            view_target,
+            view_prepass_textures,
+            view_uniform_offset,
+        ): QueryItem<Self::ViewQuery>,
+        world: &World,
+    ) -> Result<(), NodeRunError> {
+        let pipeline_cache = world.resource::<PipelineCache>();
+        let scene_bindings = world.resource::<RaytracingSceneBindings>();
+        let view_uniforms = world.resource::<ViewUniforms>();
+        let frame_count = world.resource::<FrameCount>();
+        let (
+            Some(initial_and_temporal_pipeline),
+            Some(spatial_and_shade_pipeline),
+            Some(scene_bindings),
+            Some(viewport),
+            Some(gbuffer),
+            Some(depth_buffer),
+            Some(motion_vectors),
+            Some(view_uniforms),
+        ) = (
+            pipeline_cache.get_compute_pipeline(self.initial_and_temporal_pipeline),
+            pipeline_cache.get_compute_pipeline(self.spatial_and_shade_pipeline),
+            &scene_bindings.bind_group,
+            camera.physical_viewport_size,
+            view_prepass_textures.deferred_view(),
+            view_prepass_textures.depth_view(),
+            view_prepass_textures.motion_vectors_view(),
+            view_uniforms.uniforms.binding(),
+        )
+        else {
+            return Ok(());
+        };
+
+        let bind_group = render_context.render_device().create_bind_group(
+            "solari_lighting_bind_group",
+            &self.bind_group_layout,
+            &BindGroupEntries::sequential((
+                view_target.get_unsampled_color_attachment().view,
+                solari_lighting_resources.reservoirs_a.as_entire_binding(),
+                solari_lighting_resources.reservoirs_b.as_entire_binding(),
+                gbuffer,
+                depth_buffer,
+                motion_vectors,
+                view_uniforms,
+            )),
+        );
+
+        // Choice of number here is arbitrary
+        let frame_index = frame_count.0.wrapping_mul(5782582);
+
+        let diagnostics = render_context.diagnostic_recorder();
+        let command_encoder = render_context.command_encoder();
+
+        let mut pass = command_encoder.begin_compute_pass(&ComputePassDescriptor {
+            label: Some("solari_lighting"),
+            timestamp_writes: None,
+        });
+        let pass_span = diagnostics.pass_span(&mut pass, "solari_lighting");
+
+        pass.set_bind_group(0, scene_bindings, &[]);
+        pass.set_bind_group(1, &bind_group, &[view_uniform_offset.offset]);
+
+        pass.set_pipeline(initial_and_temporal_pipeline);
+        pass.set_push_constants(
+            0,
+            bytemuck::cast_slice(&[frame_index, solari_lighting.reset as u32]),
+        );
+        pass.dispatch_workgroups(viewport.x.div_ceil(8), viewport.y.div_ceil(8), 1);
+
+        pass.set_pipeline(spatial_and_shade_pipeline);
+        pass.dispatch_workgroups(viewport.x.div_ceil(8), viewport.y.div_ceil(8), 1);
+
+        pass_span.end(&mut pass);
+
+        Ok(())
+    }
+}
+
+impl FromWorld for SolariLightingNode {
+    fn from_world(world: &mut World) -> Self {
+        let render_device = world.resource::<RenderDevice>();
+        let pipeline_cache = world.resource::<PipelineCache>();
+        let scene_bindings = world.resource::<RaytracingSceneBindings>();
+
+        let bind_group_layout = render_device.create_bind_group_layout(
+            "solari_lighting_bind_group_layout",
+            &BindGroupLayoutEntries::sequential(
+                ShaderStages::COMPUTE,
+                (
+                    texture_storage_2d(
+                        ViewTarget::TEXTURE_FORMAT_HDR,
+                        StorageTextureAccess::WriteOnly,
+                    ),
+                    storage_buffer_sized(false, None),
+                    storage_buffer_sized(false, None),
+                    texture_2d(TextureSampleType::Uint),
+                    texture_depth_2d(),
+                    texture_2d(TextureSampleType::Float { filterable: true }),
+                    uniform_buffer::<ViewUniform>(true),
+                ),
+            ),
+        );
+
+        let initial_and_temporal_pipeline =
+            pipeline_cache.queue_compute_pipeline(ComputePipelineDescriptor {
+                label: Some("solari_lighting_initial_and_temporal_pipeline".into()),
+                layout: vec![
+                    scene_bindings.bind_group_layout.clone(),
+                    bind_group_layout.clone(),
+                ],
+                push_constant_ranges: vec![PushConstantRange {
+                    stages: ShaderStages::COMPUTE,
+                    range: 0..8,
+                }],
+                shader: load_embedded_asset!(world, "restir_di.wgsl"),
+                shader_defs: vec![],
+                entry_point: "initial_and_temporal".into(),
+                zero_initialize_workgroup_memory: false,
+            });
+
+        let spatial_and_shade_pipeline =
+            pipeline_cache.queue_compute_pipeline(ComputePipelineDescriptor {
+                label: Some("solari_lighting_spatial_and_shade_pipeline".into()),
+                layout: vec![
+                    scene_bindings.bind_group_layout.clone(),
+                    bind_group_layout.clone(),
+                ],
+                push_constant_ranges: vec![PushConstantRange {
+                    stages: ShaderStages::COMPUTE,
+                    range: 0..8,
+                }],
+                shader: load_embedded_asset!(world, "restir_di.wgsl"),
+                shader_defs: vec![],
+                entry_point: "spatial_and_shade".into(),
+                zero_initialize_workgroup_memory: false,
+            });
+
+        Self {
+            bind_group_layout,
+            initial_and_temporal_pipeline,
+            spatial_and_shade_pipeline,
+        }
+    }
+}

crates/bevy_solari/src/realtime/prepare.rs

@@ -0,0 +1,65 @@
+use super::SolariLighting;
+use bevy_ecs::{
+    component::Component,
+    entity::Entity,
+    query::With,
+    system::{Commands, Query, Res},
+};
+use bevy_math::UVec2;
+use bevy_render::{
+    camera::ExtractedCamera,
+    render_resource::{Buffer, BufferDescriptor, BufferUsages},
+    renderer::RenderDevice,
+};
+
+/// Size of a Reservoir shader struct in bytes.
+const RESERVOIR_STRUCT_SIZE: u64 = 32;
+
+/// Internal rendering resources used for Solari lighting.
+#[derive(Component)]
+pub struct SolariLightingResources {
+    pub reservoirs_a: Buffer,
+    pub reservoirs_b: Buffer,
+    pub view_size: UVec2,
+}
+
+pub fn prepare_solari_lighting_resources(
+    query: Query<
+        (Entity, &ExtractedCamera, Option<&SolariLightingResources>),
+        With<SolariLighting>,
+    >,
+    render_device: Res<RenderDevice>,
+    mut commands: Commands,
+) {
+    for (entity, camera, solari_lighting_resources) in &query {
+        let Some(view_size) = camera.physical_viewport_size else {
+            continue;
+        };
+
+        if solari_lighting_resources.map(|r| r.view_size) == Some(view_size) {
+            continue;
+        }
+
+        let size = (view_size.x * view_size.y) as u64 * RESERVOIR_STRUCT_SIZE;
+
+        let reservoirs_a = render_device.create_buffer(&BufferDescriptor {
+            label: Some("solari_lighting_reservoirs_a"),
+            size,
+            usage: BufferUsages::STORAGE,
+            mapped_at_creation: false,
+        });
+
+        let reservoirs_b = render_device.create_buffer(&BufferDescriptor {
+            label: Some("solari_lighting_reservoirs_b"),
+            size,
+            usage: BufferUsages::STORAGE,
+            mapped_at_creation: false,
+        });
+
+        commands.entity(entity).insert(SolariLightingResources {
+            reservoirs_a,
+            reservoirs_b,
+            view_size,
+        });
+    }
+}

crates/bevy_solari/src/realtime/reservoir.wgsl

@@ -0,0 +1,30 @@
+// https://intro-to-restir.cwyman.org/presentations/2023ReSTIR_Course_Notes.pdf
+
+#define_import_path bevy_solari::reservoir
+
+#import bevy_solari::sampling::LightSample
+
+const NULL_RESERVOIR_SAMPLE = 0xFFFFFFFFu;
+
+// Don't adjust the size of this struct without also adjusting RESERVOIR_STRUCT_SIZE.
+struct Reservoir {
+    sample: LightSample,
+    weight_sum: f32,
+    confidence_weight: f32,
+    unbiased_contribution_weight: f32,
+    _padding: f32,
+}
+
+fn empty_reservoir() -> Reservoir {
+    return Reservoir(
+        LightSample(vec2(NULL_RESERVOIR_SAMPLE, 0u), vec2(0.0)),
+        0.0,
+        0.0,
+        0.0,
+        0.0
+    );
+}
+
+fn reservoir_valid(reservoir: Reservoir) -> bool {
+    return reservoir.sample.light_id.x != NULL_RESERVOIR_SAMPLE;
+}

crates/bevy_solari/src/realtime/restir_di.wgsl

@@ -0,0 +1,117 @@
+#import bevy_core_pipeline::tonemapping::tonemapping_luminance as luminance
+#import bevy_pbr::pbr_deferred_types::unpack_24bit_normal
+#import bevy_pbr::rgb9e5::rgb9e5_to_vec3_
+#import bevy_pbr::utils::{rand_f, octahedral_decode}
+#import bevy_render::maths::PI
+#import bevy_render::view::View
+#import bevy_solari::reservoir::{Reservoir, empty_reservoir, reservoir_valid}
+#import bevy_solari::sampling::{generate_random_light_sample, calculate_light_contribution, trace_light_visibility}
+
+@group(1) @binding(0) var view_output: texture_storage_2d<rgba16float, write>;
+@group(1) @binding(1) var<storage, read_write> reservoirs_a: array<Reservoir>;
+@group(1) @binding(2) var<storage, read_write> reservoirs_b: array<Reservoir>;
+@group(1) @binding(3) var gbuffer: texture_2d<u32>;
+@group(1) @binding(4) var depth_buffer: texture_depth_2d;
+@group(1) @binding(5) var motion_vectors: texture_2d<f32>;
+@group(1) @binding(6) var<uniform> view: View;
+struct PushConstants { frame_index: u32, reset: u32 }
+var<push_constant> constants: PushConstants;
+
+const INITIAL_SAMPLES = 32u;
+const SPATIAL_REUSE_RADIUS_PIXELS = 30.0;
+const CONFIDENCE_WEIGHT_CAP = 20.0 * f32(INITIAL_SAMPLES);
+
+@compute @workgroup_size(8, 8, 1)
+fn initial_and_temporal(@builtin(global_invocation_id) global_id: vec3<u32>) {
+    if any(global_id.xy >= vec2u(view.viewport.zw)) { return; }
+
+    let pixel_index = global_id.x + global_id.y * u32(view.viewport.z);
+    var rng = pixel_index + constants.frame_index;
+
+    let depth = textureLoad(depth_buffer, global_id.xy, 0);
+    if depth == 0.0 {
+        reservoirs_b[pixel_index] = empty_reservoir();
+        return;
+    }
+    let gpixel = textureLoad(gbuffer, global_id.xy, 0);
+    let world_position = reconstruct_world_position(global_id.xy, depth);
+    let world_normal = octahedral_decode(unpack_24bit_normal(gpixel.a));
+    let base_color = pow(unpack4x8unorm(gpixel.r).rgb, vec3(2.2));
+    let diffuse_brdf = base_color / PI;
+
+    let initial_reservoir = generate_initial_reservoir(world_position, world_normal, diffuse_brdf, &rng);
+
+    reservoirs_b[pixel_index] = initial_reservoir;
+}
+
+@compute @workgroup_size(8, 8, 1)
+fn spatial_and_shade(@builtin(global_invocation_id) global_id: vec3<u32>) {
+    if any(global_id.xy >= vec2u(view.viewport.zw)) { return; }
+
+    let pixel_index = global_id.x + global_id.y * u32(view.viewport.z);
+    var rng = pixel_index + constants.frame_index;
+
+    let depth = textureLoad(depth_buffer, global_id.xy, 0);
+    if depth == 0.0 {
+        reservoirs_a[pixel_index] = empty_reservoir();
+        textureStore(view_output, global_id.xy, vec4(vec3(0.0), 1.0));
+        return;
+    }
+    let gpixel = textureLoad(gbuffer, global_id.xy, 0);
+    let world_position = reconstruct_world_position(global_id.xy, depth);
+    let world_normal = octahedral_decode(unpack_24bit_normal(gpixel.a));
+    let base_color = pow(unpack4x8unorm(gpixel.r).rgb, vec3(2.2));
+    let diffuse_brdf = base_color / PI;
+    let emissive = rgb9e5_to_vec3_(gpixel.g);
+
+    let input_reservoir = reservoirs_b[pixel_index];
+
+    var radiance = vec3(0.0);
+    if reservoir_valid(input_reservoir) {
+        radiance = calculate_light_contribution(input_reservoir.sample, world_position, world_normal).radiance;
+    }
+
+    reservoirs_a[pixel_index] = input_reservoir;
+
+    var pixel_color = radiance * input_reservoir.unbiased_contribution_weight;
+    pixel_color *= view.exposure;
+    pixel_color *= diffuse_brdf;
+    pixel_color += emissive;
+    textureStore(view_output, global_id.xy, vec4(pixel_color, 1.0));
+}
+
+fn generate_initial_reservoir(world_position: vec3<f32>, world_normal: vec3<f32>, diffuse_brdf: vec3<f32>, rng: ptr<function, u32>) -> Reservoir{
+    var reservoir = empty_reservoir();
+    var reservoir_target_function = 0.0;
+    for (var i = 0u; i < INITIAL_SAMPLES; i++) {
+        let light_sample = generate_random_light_sample(rng);
+
+        let mis_weight = 1.0 / f32(INITIAL_SAMPLES);
+        let light_contribution = calculate_light_contribution(light_sample, world_position, world_normal);
+        let target_function = luminance(light_contribution.radiance * diffuse_brdf);
+        let resampling_weight = mis_weight * (target_function * light_contribution.inverse_pdf);
+
+        reservoir.weight_sum += resampling_weight;
+
+        if rand_f(rng) < resampling_weight / reservoir.weight_sum {
+            reservoir.sample = light_sample;
+            reservoir_target_function = target_function;
+        }
+    }
+
+    if reservoir_valid(reservoir) {
+        let inverse_target_function = select(0.0, 1.0 / reservoir_target_function, reservoir_target_function > 0.0);
+        reservoir.unbiased_contribution_weight = reservoir.weight_sum * inverse_target_function;
+        reservoir.unbiased_contribution_weight *= trace_light_visibility(reservoir.sample, world_position);
+    }
+
+    reservoir.confidence_weight = f32(INITIAL_SAMPLES);
+    return reservoir;
+}
+
+fn reconstruct_world_position(pixel_id: vec2<u32>, depth: f32) -> vec3<f32> {
+    let uv = (vec2<f32>(pixel_id) + 0.5) / view.viewport.zw;
+    let xy_ndc = (uv - vec2(0.5)) * vec2(2.0, -2.0);
+    let world_pos = view.world_from_clip * vec4(xy_ndc, depth, 1.0);
+    return world_pos.xyz / world_pos.w;
+}

crates/bevy_solari/src/scene/raytracing_scene_bindings.wgsl

@@ -71,7 +71,7 @@ struct DirectionalLight {
 @group(0) @binding(9) var<storage> light_sources: array<LightSource>;
 @group(0) @binding(10) var<storage> directional_lights: array<DirectionalLight>;
 
-const RAY_T_MIN = 0.0001;
+const RAY_T_MIN = 0.01;
 const RAY_T_MAX = 100000.0;
 
 const RAY_NO_CULL = 0xFFu;

crates/bevy_solari/src/scene/sampling.wgsl

@@ -69,6 +69,7 @@ fn calculate_light_contribution(light_sample: LightSample, ray_origin: vec3<f32>
 fn calculate_directional_light_contribution(light_sample: LightSample, directional_light_id: u32, origin_world_normal: vec3<f32>) -> LightContribution {
     let directional_light = directional_lights[directional_light_id];
 
+#ifdef DIRECTIONAL_LIGHT_SOFT_SHADOWS
     // Sample a random direction within a cone whose base is the sun approximated as a disk
     // https://www.realtimerendering.com/raytracinggems/unofficial_RayTracingGems_v1.9.pdf#0004286901.INDD%3ASec30%3A305
     let cos_theta = (1.0 - light_sample.random.x) + light_sample.random.x * directional_light.cos_theta_max;
@@ -80,6 +81,9 @@ fn calculate_directional_light_contribution(light_sample: LightSample, direction
 
     // Rotate the ray so that the cone it was sampled from is aligned with the light direction
     ray_direction = build_orthonormal_basis(directional_light.direction_to_light) * ray_direction;
+#else
+    let ray_direction = directional_light.direction_to_light;
+#endif
 
     let cos_theta_origin = saturate(dot(ray_direction, origin_world_normal));
     let radiance = directional_light.luminance * cos_theta_origin;
@@ -119,6 +123,7 @@ fn trace_light_visibility(light_sample: LightSample, ray_origin: vec3<f32>) -> f
 fn trace_directional_light_visibility(light_sample: LightSample, directional_light_id: u32, ray_origin: vec3<f32>) -> f32 {
     let directional_light = directional_lights[directional_light_id];
 
+#ifdef DIRECTIONAL_LIGHT_SOFT_SHADOWS
     // Sample a random direction within a cone whose base is the sun approximated as a disk
     // https://www.realtimerendering.com/raytracinggems/unofficial_RayTracingGems_v1.9.pdf#0004286901.INDD%3ASec30%3A305
     let cos_theta = (1.0 - light_sample.random.x) + light_sample.random.x * directional_light.cos_theta_max;
@@ -130,6 +135,9 @@ fn trace_directional_light_visibility(light_sample: LightSample, directional_lig
 
     // Rotate the ray so that the cone it was sampled from is aligned with the light direction
     ray_direction = build_orthonormal_basis(directional_light.direction_to_light) * ray_direction;
+#else
+    let ray_direction = directional_light.direction_to_light;
+#endif
 
     let ray_hit = trace_ray(ray_origin, ray_direction, RAY_T_MIN, RAY_T_MAX, RAY_FLAG_TERMINATE_ON_FIRST_HIT);
     return f32(ray_hit.kind == RAY_QUERY_INTERSECTION_NONE);

examples/3d/solari.rs

@@ -1,28 +1,45 @@
-//! Demonstrates realtime dynamic global illumination rendering using Bevy Solari.
+//! Demonstrates realtime dynamic raytraced lighting using Bevy Solari.
 
 #[path = "../helpers/camera_controller.rs"]
 mod camera_controller;
 
+use argh::FromArgs;
 use bevy::{
     prelude::*,
     render::{camera::CameraMainTextureUsages, mesh::Indices, render_resource::TextureUsages},
     scene::SceneInstanceReady,
     solari::{
-        pathtracer::Pathtracer,
-        prelude::{RaytracingMesh3d, SolariPlugin},
+        pathtracer::{Pathtracer, PathtracingPlugin},
+        prelude::{RaytracingMesh3d, SolariLighting, SolariPlugin},
     },
 };
 use camera_controller::{CameraController, CameraControllerPlugin};
 use std::f32::consts::PI;
 
-fn main() {
-    App::new()
-        .add_plugins((DefaultPlugins, SolariPlugin, CameraControllerPlugin))
-        .add_systems(Startup, setup)
-        .run();
+/// `bevy_solari` demo.
+#[derive(FromArgs, Resource, Clone, Copy)]
+struct Args {
+    /// use the reference pathtracer instead of the realtime lighting system.
+    #[argh(switch)]
+    pathtracer: Option<bool>,
 }
 
-fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
+fn main() {
+    let args: Args = argh::from_env();
+
+    let mut app = App::new();
+    app.add_plugins((DefaultPlugins, SolariPlugin, CameraControllerPlugin))
+        .insert_resource(args)
+        .add_systems(Startup, setup);
+
+    if args.pathtracer == Some(true) {
+        app.add_plugins(PathtracingPlugin);
+    }
+
+    app.run();
+}
+
+fn setup(mut commands: Commands, asset_server: Res<AssetServer>, args: Res<Args>) {
     commands
         .spawn(SceneRoot(asset_server.load(
             GltfAssetLabel::Scene(0).from_asset("models/CornellBox/CornellBox.glb"),
@@ -32,13 +49,13 @@ fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
     commands.spawn((
         DirectionalLight {
             illuminance: light_consts::lux::FULL_DAYLIGHT,
-            shadows_enabled: true,
+            shadows_enabled: false, // Solari replaces shadow mapping
             ..default()
         },
         Transform::from_rotation(Quat::from_euler(EulerRot::XYZ, PI * -0.43, PI * -0.08, 0.0)),
     ));
 
-    commands.spawn((
+    let mut camera = commands.spawn((
         Camera3d::default(),
         Camera {
             clear_color: ClearColorConfig::Custom(Color::BLACK),
@@ -49,10 +66,16 @@ fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
             run_speed: 1500.0,
             ..Default::default()
         },
-        Pathtracer::default(),
-        CameraMainTextureUsages::default().with(TextureUsages::STORAGE_BINDING),
         Transform::from_xyz(-278.0, 273.0, 800.0),
+        // Msaa::Off and CameraMainTextureUsages with STORAGE_BINDING are required for Solari
+        CameraMainTextureUsages::default().with(TextureUsages::STORAGE_BINDING),
+        Msaa::Off,
     ));
+    if args.pathtracer == Some(true) {
+        camera.insert(Pathtracer::default());
+    } else {
+        camera.insert(SolariLighting::default());
+    }
 }
 
 fn add_raytracing_meshes_on_scene_load(
@@ -60,11 +83,14 @@ fn add_raytracing_meshes_on_scene_load(
     children: Query<&Children>,
     mesh: Query<&Mesh3d>,
     mut meshes: ResMut<Assets<Mesh>>,
+    mut materials: ResMut<Assets<StandardMaterial>>,
     mut commands: Commands,
+    args: Res<Args>,
 ) {
-    // Ensure meshes are bery_solari compatible
+    // Ensure meshes are bevy_solari compatible
     for (_, mesh) in meshes.iter_mut() {
         mesh.remove_attribute(Mesh::ATTRIBUTE_UV_1.id);
+        mesh.remove_attribute(Mesh::ATTRIBUTE_COLOR.id);
         mesh.generate_tangents().unwrap();
 
         if let Some(indices) = mesh.indices_mut() {
@@ -74,12 +100,21 @@ fn add_raytracing_meshes_on_scene_load(
         }
     }
 
+    // Add raytracing mesh handles
     for descendant in children.iter_descendants(trigger.target()) {
         if let Ok(mesh) = mesh.get(descendant) {
             commands
                 .entity(descendant)
-                .insert(RaytracingMesh3d(mesh.0.clone()))
-                .remove::<Mesh3d>();
+                .insert(RaytracingMesh3d(mesh.0.clone()));
+
+            if args.pathtracer == Some(true) {
+                commands.entity(descendant).remove::<Mesh3d>();
+            }
         }
     }
+
+    // Increase material emissive intensity to make it prettier for the example
+    for (_, material) in materials.iter_mut() {
+        material.emissive *= 200.0;
+    }
 }

examples/README.md

@@ -185,7 +185,7 @@ Example | Description
 [Shadow Biases](../examples/3d/shadow_biases.rs) | Demonstrates how shadow biases affect shadows in a 3d scene
 [Shadow Caster and Receiver](../examples/3d/shadow_caster_receiver.rs) | Demonstrates how to prevent meshes from casting/receiving shadows in a 3d scene
 [Skybox](../examples/3d/skybox.rs) | Load a cubemap texture onto a cube like a skybox and cycle through different compressed texture formats.
-[Solari](../examples/3d/solari.rs) | Demonstrates realtime dynamic global illumination rendering using Bevy Solari.
+[Solari](../examples/3d/solari.rs) | Demonstrates realtime dynamic raytraced lighting using Bevy Solari.
 [Specular Tint](../examples/3d/specular_tint.rs) | Demonstrates specular tints and maps
 [Spherical Area Lights](../examples/3d/spherical_area_lights.rs) | Demonstrates how point light radius values affect light behavior
 [Split Screen](../examples/3d/split_screen.rs) | Demonstrates how to render two cameras to the same window to accomplish "split screen"

typos.toml

@@ -13,6 +13,7 @@ LOD = "LOD"                             # Level of detail
 reparametrization = "reparametrization" # Mathematical term in curve context (reparameterize)
 reparametrize = "reparametrize"
 reparametrized = "reparametrized"
+mis = "mis"                             # mis - multiple importance sampling
 
 # Match a Whole Word - Case Sensitive
 [default.extend-identifiers]