Reduce the clusterable object UBO size below 16384 for WebGL 2.

crates/bevy_pbr/src/cluster/mod.rs

@@ -33,8 +33,13 @@ mod assign;
 #[cfg(test)]
 mod test;
 
-// NOTE: this must be kept in sync with the same constants in pbr.frag
-pub const MAX_UNIFORM_BUFFER_CLUSTERABLE_OBJECTS: usize = 256;
+// NOTE: this must be kept in sync with the same constants in
+// `mesh_view_types.wgsl`.
+pub const MAX_UNIFORM_BUFFER_CLUSTERABLE_OBJECTS: usize = 204;
+// Make sure that the clusterable object buffer doesn't overflow the maximum
+// size of a UBO on WebGL 2.
+const _: () =
+    assert!(size_of::<GpuClusterableObject>() * MAX_UNIFORM_BUFFER_CLUSTERABLE_OBJECTS <= 16384);
 
 // NOTE: Clustered-forward rendering requires 3 storage buffer bindings so check that
 // at least that many are supported using this constant and SupportedBindingType::from_device()
@@ -811,8 +816,8 @@ impl ViewClusterBuffers {
 }
 
 // NOTE: With uniform buffer max binding size as 16384 bytes
-// that means we can fit 256 clusterable objects in one uniform
-// buffer, which means the count can be at most 256 so it
+// that means we can fit 204 clusterable objects in one uniform
+// buffer, which means the count can be at most 204 so it
 // needs 9 bits.
 // The array of indices can also use u8 and that means the
 // offset in to the array of indices needs to be able to address

crates/bevy_pbr/src/render/mesh_view_types.wgsl

@@ -105,7 +105,7 @@ struct ClusterOffsetsAndCounts {
 };
 #else
 struct ClusterableObjects {
-    data: array<ClusterableObject, 256u>,
+    data: array<ClusterableObject, 204u>,
 };
 struct ClusterLightIndexLists {
     // each u32 contains 4 u8 indices into the ClusterableObjects array