Implement bindless lightmaps.

assets/shaders/bindless_material.wgsl

@@ -18,7 +18,7 @@ struct Color {
 @fragment
 fn fragment(in: VertexOutput) -> @location(0) vec4<f32> {
 #ifdef BINDLESS
-    let slot = mesh[in.instance_index].material_bind_group_slot;
+    let slot = mesh[in.instance_index].material_and_lightmap_bind_group_slot & 0xffffu;
     let base_color = material_color[slot].base_color;
 #else   // BINDLESS
     let base_color = material_color.base_color;

crates/bevy_core_pipeline/src/core_3d/mod.rs

@@ -76,10 +76,10 @@ pub use main_opaque_pass_3d_node::*;
 pub use main_transparent_pass_3d_node::*;
 
 use bevy_app::{App, Plugin, PostUpdate};
-use bevy_asset::{AssetId, UntypedAssetId};
+use bevy_asset::UntypedAssetId;
 use bevy_color::LinearRgba;
 use bevy_ecs::{entity::EntityHashSet, prelude::*};
-use bevy_image::{BevyDefault, Image};
+use bevy_image::BevyDefault;
 use bevy_math::FloatOrd;
 use bevy_render::{
     camera::{Camera, ExtractedCamera},
@@ -102,6 +102,7 @@ use bevy_render::{
     Extract, ExtractSchedule, Render, RenderApp, RenderSet,
 };
 use bevy_utils::{tracing::warn, HashMap};
+use nonmax::NonMaxU32;
 
 use crate::{
     core_3d::main_transmissive_pass_3d_node::MainTransmissivePass3dNode,
@@ -258,8 +259,9 @@ pub struct Opaque3dBatchSetKey {
     /// For non-mesh items, you can safely fill this with `None`.
     pub index_slab: Option<SlabId>,
 
-    /// The lightmap, if present.
-    pub lightmap_image: Option<AssetId<Image>>,
+    /// Index of the slab that the lightmap resides in, if a lightmap is
+    /// present.
+    pub lightmap_slab: Option<NonMaxU32>,
 }
 
 /// Data that must be identical in order to *batch* phase items together.

crates/bevy_pbr/src/lightmap/lightmap.wgsl

@@ -2,8 +2,13 @@
 
 #import bevy_pbr::mesh_bindings::mesh
 
+#ifdef MULTIPLE_LIGHTMAPS_IN_ARRAY
+@group(1) @binding(4) var lightmaps_textures: binding_array<texture_2d<f32>>;
+@group(1) @binding(5) var lightmaps_samplers: binding_array<sampler>;
+#else   // MULTIPLE_LIGHTMAPS_IN_ARRAY
 @group(1) @binding(4) var lightmaps_texture: texture_2d<f32>;
 @group(1) @binding(5) var lightmaps_sampler: sampler;
+#endif  // MULTIPLE_LIGHTMAPS_IN_ARRAY
 
 // Samples the lightmap, if any, and returns indirect illumination from it.
 fn lightmap(uv: vec2<f32>, exposure: f32, instance_index: u32) -> vec3<f32> {
@@ -21,9 +26,20 @@ fn lightmap(uv: vec2<f32>, exposure: f32, instance_index: u32) -> vec3<f32> {
     // control flow uniformity problems.
     //
     // TODO(pcwalton): Consider bicubic filtering.
+#ifdef MULTIPLE_LIGHTMAPS_IN_ARRAY
+    let lightmap_slot = mesh[instance_index].material_and_lightmap_bind_group_slot >> 16u;
+    return textureSampleLevel(
+        lightmaps_textures[lightmap_slot],
+        lightmaps_samplers[lightmap_slot],
+        lightmap_uv,
+        0.0
+    ).rgb * exposure;
+#else   // MULTIPLE_LIGHTMAPS_IN_ARRAY
     return textureSampleLevel(
         lightmaps_texture,
         lightmaps_sampler,
         lightmap_uv,
-        0.0).rgb * exposure;
+        0.0
+    ).rgb * exposure;
+#endif  // MULTIPLE_LIGHTMAPS_IN_ARRAY
 }