Disable clustered decals on Metal. (#17554)

Unfortunately, Apple platforms don't have enough texture bindings to
properly support clustered decals. This should be fixed once `wgpu` has
first-class bindless texture support. In the meantime, we disable them.

Closes #17553.

---------

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

Author: pcwalton

crates/bevy_pbr/src/cluster/assign.rs

@@ -21,7 +21,8 @@ use bevy_utils::prelude::default;
 use tracing::warn;
 
 use crate::{
-    binding_arrays_are_usable, decal::clustered::ClusteredDecal, prelude::EnvironmentMapLight,
+    decal::{self, clustered::ClusteredDecal},
+    prelude::EnvironmentMapLight,
     ClusterConfig, ClusterFarZMode, Clusters, ExtractedPointLight, GlobalVisibleClusterableObjects,
     LightProbe, PointLight, SpotLight, ViewClusterBindings, VisibleClusterableObjects,
     VolumetricLight, CLUSTERED_FORWARD_STORAGE_BUFFER_COUNT,
@@ -257,7 +258,8 @@ pub(crate) fn assign_objects_to_clusters(
         ));
     }
 
-    if binding_arrays_are_usable(&render_device, &render_adapter) {
+    // Add decals if the current platform supports them.
+    if decal::clustered::clustered_decals_are_usable(&render_device, &render_adapter) {
         clusterable_objects.extend(decals_query.iter().map(|(entity, transform)| {
             ClusterableObjectAssignmentData {
                 entity,

crates/bevy_pbr/src/decal/clustered.rs

@@ -6,8 +6,8 @@
 //!
 //! Clustered decals are the highest-quality types of decals that Bevy supports,
 //! but they require bindless textures. This means that they presently can't be
-//! used on WebGL 2 or WebGPU. Bevy's clustered decals can be used with forward
-//! or deferred rendering and don't require a prepass.
+//! used on WebGL 2, WebGPU, macOS, or iOS. Bevy's clustered decals can be used
+//! with forward or deferred rendering and don't require a prepass.
 //!
 //! On their own, clustered decals only project the base color of a texture. You
 //! can, however, use the built-in *tag* field to customize the appearance of a
@@ -77,8 +77,8 @@ pub struct ClusteredDecalPlugin;
 ///
 /// Clustered decals are the highest-quality types of decals that Bevy supports,
 /// but they require bindless textures. This means that they presently can't be
-/// used on WebGL 2 or WebGPU. Bevy's clustered decals can be used with forward
-/// or deferred rendering and don't require a prepass.
+/// used on WebGL 2, WebGPU, macOS, or iOS. Bevy's clustered decals can be used
+/// with forward or deferred rendering and don't require a prepass.
 #[derive(Component, Debug, Clone, Reflect, ExtractComponent)]
 #[reflect(Component, Debug)]
 #[require(Transform, Visibility, VisibilityClass)]
@@ -263,7 +263,7 @@ pub(crate) fn get_bind_group_layout_entries(
 ) -> Option<[BindGroupLayoutEntryBuilder; 3]> {
     // If binding arrays aren't supported on the current platform, we have no
     // bind group layout entries.
-    if !binding_arrays_are_usable(render_device, render_adapter) {
+    if !clustered_decals_are_usable(render_device, render_adapter) {
         return None;
     }
 
@@ -290,7 +290,7 @@ impl<'a> RenderViewClusteredDecalBindGroupEntries<'a> {
         render_adapter: &RenderAdapter,
     ) -> Option<RenderViewClusteredDecalBindGroupEntries<'a>> {
         // Skip the entries if decals are unsupported on the current platform.
-        if !binding_arrays_are_usable(render_device, render_adapter) {
+        if !clustered_decals_are_usable(render_device, render_adapter) {
             return None;
         }
 
@@ -367,3 +367,19 @@ fn upload_decals(
 
     decals_buffer.write_buffer(&render_device, &render_queue);
 }
+
+/// Returns true if clustered decals are usable on the current platform or false
+/// otherwise.
+///
+/// Clustered decals are currently disabled on macOS and iOS due to insufficient
+/// texture bindings and limited bindless support in `wgpu`.
+pub fn clustered_decals_are_usable(
+    render_device: &RenderDevice,
+    render_adapter: &RenderAdapter,
+) -> bool {
+    // Disable binding arrays on Metal. There aren't enough texture bindings available.
+    // See issue #17553.
+    // Re-enable this when `wgpu` has first-class bindless.
+    binding_arrays_are_usable(render_device, render_adapter)
+        && cfg!(not(any(target_os = "macos", target_os = "ios")))
+}

crates/bevy_pbr/src/render/mesh.rs

@@ -1528,6 +1528,9 @@ pub struct MeshPipeline {
     /// This affects whether reflection probes can be used.
     pub binding_arrays_are_usable: bool,
 
+    /// Whether clustered decals are usable on the current render device.
+    pub clustered_decals_are_usable: bool,
+
     /// Whether skins will use uniform buffers on account of storage buffers
     /// being unavailable on this platform.
     pub skins_use_uniform_buffers: bool,
@@ -1589,6 +1592,10 @@ impl FromWorld for MeshPipeline {
             mesh_layouts: MeshLayouts::new(&render_device, &render_adapter),
             per_object_buffer_batch_size: GpuArrayBuffer::<MeshUniform>::batch_size(&render_device),
             binding_arrays_are_usable: binding_arrays_are_usable(&render_device, &render_adapter),
+            clustered_decals_are_usable: decal::clustered::clustered_decals_are_usable(
+                &render_device,
+                &render_adapter,
+            ),
             skins_use_uniform_buffers: skin::skins_use_uniform_buffers(&render_device),
         }
     }
@@ -2295,7 +2302,7 @@ impl SpecializedMeshPipeline for MeshPipeline {
             shader_defs.push("IRRADIANCE_VOLUMES_ARE_USABLE".into());
         }
 
-        if self.binding_arrays_are_usable {
+        if self.clustered_decals_are_usable {
             shader_defs.push("CLUSTERED_DECALS_ARE_USABLE".into());
         }
 

examples/3d/clustered_decals.rs

@@ -2,16 +2,22 @@
 
 use std::f32::consts::{FRAC_PI_3, PI};
 use std::fmt::{self, Formatter};
+use std::process;
 
-use bevy::pbr::{ExtendedMaterial, MaterialExtension};
-use bevy::window::SystemCursorIcon;
-use bevy::winit::cursor::CursorIcon;
 use bevy::{
     color::palettes::css::{LIME, ORANGE_RED, SILVER},
     input::mouse::AccumulatedMouseMotion,
-    pbr::decal::clustered::ClusteredDecal,
+    pbr::{
+        decal::{self, clustered::ClusteredDecal},
+        ExtendedMaterial, MaterialExtension,
+    },
     prelude::*,
-    render::render_resource::{AsBindGroup, ShaderRef},
+    render::{
+        render_resource::{AsBindGroup, ShaderRef},
+        renderer::{RenderAdapter, RenderDevice},
+    },
+    window::SystemCursorIcon,
+    winit::cursor::CursorIcon,
 };
 use ops::{acos, cos, sin};
 use widgets::{
@@ -152,9 +158,17 @@ fn setup(
     mut commands: Commands,
     asset_server: Res<AssetServer>,
     app_status: Res<AppStatus>,
+    render_device: Res<RenderDevice>,
+    render_adapter: Res<RenderAdapter>,
     mut meshes: ResMut<Assets<Mesh>>,
     mut materials: ResMut<Assets<ExtendedMaterial<StandardMaterial, CustomDecalExtension>>>,
 ) {
+    // Error out if clustered decals aren't supported on the current platform.
+    if !decal::clustered::clustered_decals_are_usable(&render_device, &render_adapter) {
+        eprintln!("Clustered decals aren't usable on this platform.");
+        process::exit(1);
+    }
+
     spawn_cube(&mut commands, &mut meshes, &mut materials);
     spawn_camera(&mut commands);
     spawn_light(&mut commands);