1#import bevy_pbr::forward_io::VertexOutput
2#import bevy_pbr::irradiance_volume
3#import bevy_pbr::mesh_view_bindings
4#import bevy_pbr::clustered_forward
5
6struct VoxelVisualizationIrradianceVolumeInfo {
7    world_from_voxel: mat4x4<f32>,
8    voxel_from_world: mat4x4<f32>,
9    resolution: vec3<u32>,
10    // A scale factor that's applied to the diffuse and specular light from the
11    // light probe. This is in units of cd/m² (candela per square meter).
12    intensity: f32,
13}
14
15@group(#{MATERIAL_BIND_GROUP}) @binding(100)
16var<uniform> irradiance_volume_info: VoxelVisualizationIrradianceVolumeInfo;
17
18@fragment
19fn fragment(mesh: VertexOutput) -> @location(0) vec4<f32> {
20    // Snap the world position we provide to `irradiance_volume_light()` to the
21    // middle of the nearest texel.
22    var unit_pos = (irradiance_volume_info.voxel_from_world *
23        vec4(mesh.world_position.xyz, 1.0f)).xyz;
24    let resolution = vec3<f32>(irradiance_volume_info.resolution);
25    let stp = clamp((unit_pos + 0.5) * resolution, vec3(0.5f), resolution - vec3(0.5f));
26    let stp_rounded = round(stp - 0.5f) + 0.5f;
27    let rounded_world_pos = (irradiance_volume_info.world_from_voxel * vec4(stp_rounded, 1.0f)).xyz;
28
29    // Look up the irradiance volume range in the cluster list.
30    let view_z = dot(vec4<f32>(
31        mesh_view_bindings::view.view_from_world[0].z,
32        mesh_view_bindings::view.view_from_world[1].z,
33        mesh_view_bindings::view.view_from_world[2].z,
34        mesh_view_bindings::view.view_from_world[3].z
35    ), mesh.world_position);
36    let cluster_index = clustered_forward::view_fragment_cluster_index(mesh.position.xy, view_z, false);
37    var clusterable_object_index_ranges =
38        clustered_forward::unpack_clusterable_object_index_ranges(cluster_index);
39
40    // `irradiance_volume_light()` multiplies by intensity, so cancel it out.
41    // If we take intensity into account, the cubes will be way too bright.
42    let rgb = irradiance_volume::irradiance_volume_light(
43        mesh.world_position.xyz,
44        mesh.world_normal,
45        &clusterable_object_index_ranges,
46    ) / irradiance_volume_info.intensity;
47
48    return vec4<f32>(rgb, 1.0f);
49}