Implement irradiance volumes.

Cargo.toml

@@ -935,6 +935,17 @@ description = "Showcases wireframe rendering"
 category = "3D Rendering"
 wasm = false
 
+[[example]]
+name = "irradiance_volumes"
+path = "examples/3d/irradiance_volumes.rs"
+doc-scrape-examples = true
+
+[package.metadata.example.irradiance_volumes]
+name = "Irradiance Volumes"
+description = "Demonstrates irradiance volumes"
+category = "3D Rendering"
+wasm = false
+
 [[example]]
 name = "lightmaps"
 path = "examples/3d/lightmaps.rs"

assets/shaders/irradiance_volume_voxel_visualization.wgsl

@@ -0,0 +1,35 @@
+#import bevy_pbr::forward_io::VertexOutput
+#import bevy_pbr::irradiance_volume
+#import bevy_pbr::mesh_view_bindings
+
+struct VoxelVisualizationIrradianceVolumeInfo {
+    transform: mat4x4<f32>,
+    inverse_transform: mat4x4<f32>,
+    resolution: vec3<u32>,
+    // A scale factor that's applied to the diffuse and specular light from the
+    // light probe. This is in units of cd/m² (candela per square meter).
+    intensity: f32,
+}
+
+@group(2) @binding(100)
+var<uniform> irradiance_volume_info: VoxelVisualizationIrradianceVolumeInfo;
+
+@fragment
+fn fragment(mesh: VertexOutput) -> @location(0) vec4<f32> {
+    // Snap the world position we provide to `irradiance_volume_light()` to the
+    // middle of the nearest texel.
+    var unit_pos = (irradiance_volume_info.inverse_transform *
+        vec4(mesh.world_position.xyz, 1.0f)).xyz;
+    let resolution = vec3<f32>(irradiance_volume_info.resolution);
+    let stp = clamp((unit_pos + 0.5) * resolution, vec3(0.5f), resolution - vec3(0.5f));
+    let stp_rounded = round(stp - 0.5f) + 0.5f;
+    let rounded_world_pos = (irradiance_volume_info.transform * vec4(stp_rounded, 1.0f)).xyz;
+
+    // `irradiance_volume_light()` multiplies by intensity, so cancel it out.
+    // If we take intensity into account, the cubes will be way too bright.
+    let rgb = irradiance_volume::irradiance_volume_light(
+        mesh.world_position.xyz,
+        mesh.world_normal) / irradiance_volume_info.intensity;
+
+    return vec4<f32>(rgb, 1.0f);
+}

crates/bevy_core_pipeline/src/tonemapping/tonemapping_shared.wgsl

@@ -7,8 +7,8 @@
     @group(0) @binding(3) var dt_lut_texture: texture_3d<f32>;
     @group(0) @binding(4) var dt_lut_sampler: sampler;
 #else
-    @group(0) @binding(16) var dt_lut_texture: texture_3d<f32>;
-    @group(0) @binding(17) var dt_lut_sampler: sampler;
+    @group(0) @binding(18) var dt_lut_texture: texture_3d<f32>;
+    @group(0) @binding(19) var dt_lut_sampler: sampler;
 #endif
 
 fn sample_current_lut(p: vec3<f32>) -> vec3<f32> {

crates/bevy_pbr/src/deferred/mod.rs

@@ -1,6 +1,7 @@
 use crate::{
-    environment_map::RenderViewEnvironmentMaps, graph::LabelsPbr, MeshPipeline, MeshViewBindGroup,
-    ScreenSpaceAmbientOcclusionSettings, ViewLightProbesUniformOffset,
+    graph::LabelsPbr, irradiance_volume::IrradianceVolume, prelude::EnvironmentMapLight,
+    MeshPipeline, MeshViewBindGroup, RenderViewLightProbes, ScreenSpaceAmbientOcclusionSettings,
+    ViewLightProbesUniformOffset,
 };
 use bevy_app::prelude::*;
 use bevy_asset::{load_internal_asset, Handle};
@@ -284,6 +285,10 @@ impl SpecializedRenderPipeline for DeferredLightingLayout {
             shader_defs.push("ENVIRONMENT_MAP".into());
         }
 
+        if key.contains(MeshPipelineKey::IRRADIANCE_VOLUME) {
+            shader_defs.push("IRRADIANCE_VOLUME".into());
+        }
+
         if key.contains(MeshPipelineKey::NORMAL_PREPASS) {
             shader_defs.push("NORMAL_PREPASS".into());
         }
@@ -407,7 +412,8 @@ pub fn prepare_deferred_lighting_pipelines(
                 Has<DepthPrepass>,
                 Has<MotionVectorPrepass>,
             ),
-            Has<RenderViewEnvironmentMaps>,
+            Has<RenderViewLightProbes<EnvironmentMapLight>>,
+            Has<RenderViewLightProbes<IrradianceVolume>>,
         ),
         With<DeferredPrepass>,
     >,
@@ -421,6 +427,7 @@ pub fn prepare_deferred_lighting_pipelines(
         ssao,
         (normal_prepass, depth_prepass, motion_vector_prepass),
         has_environment_maps,
+        has_irradiance_volumes,
     ) in &views
     {
         let mut view_key = MeshPipelineKey::from_hdr(view.hdr);
@@ -474,6 +481,10 @@ pub fn prepare_deferred_lighting_pipelines(
             view_key |= MeshPipelineKey::ENVIRONMENT_MAP;
         }
 
+        if has_irradiance_volumes {
+            view_key |= MeshPipelineKey::IRRADIANCE_VOLUME;
+        }
+
         match shadow_filter_method.unwrap_or(&ShadowFilteringMethod::default()) {
             ShadowFilteringMethod::Hardware2x2 => {
                 view_key |= MeshPipelineKey::SHADOW_FILTER_METHOD_HARDWARE_2X2;