make Prepass/ShadowsEnabled methods on Material (#20999)

# Objective

- enabling prepass/shadows should be done like the rest of a material's
properties

## Solution

- remove `Prepass/ShadowsEnabled` resources and associated fields on
`MaterialPlugin`
- add `Material::enable_prepass` and `Material::enable_shadows`

Author: ecoskey

crates/bevy_pbr/src/decal/forward.rs

@@ -41,8 +41,6 @@ impl Plugin for ForwardDecalPlugin {
         app.insert_resource(ForwardDecalMesh(mesh));
 
         app.add_plugins(MaterialPlugin::<ForwardDecalMaterial<StandardMaterial>> {
-            prepass_enabled: false,
-            shadows_enabled: false,
             debug_flags: RenderDebugFlags::default(),
             ..Default::default()
         });

crates/bevy_pbr/src/extended_material.rs

@@ -48,6 +48,19 @@ pub trait MaterialExtension: Asset + AsBindGroup + Clone + Sized {
         None
     }
 
+    /// Controls if the prepass is enabled for the Material.
+    /// For more information about what a prepass is, see the [`bevy_core_pipeline::prepass`] docs.
+    #[inline]
+    fn enable_prepass() -> bool {
+        true
+    }
+
+    /// Controls if shadows are enabled for the Material.
+    #[inline]
+    fn enable_shadows() -> bool {
+        true
+    }
+
     /// Returns this material's prepass vertex shader. If [`ShaderRef::Default`] is returned, the base material prepass vertex shader
     /// will be used.
     fn prepass_vertex_shader() -> ShaderRef {
@@ -325,6 +338,14 @@ impl<B: Material, E: MaterialExtension> Material for ExtendedMaterial<B, E> {
         B::reads_view_transmission_texture(&self.base)
     }
 
+    fn enable_prepass() -> bool {
+        E::enable_prepass()
+    }
+
+    fn enable_shadows() -> bool {
+        E::enable_prepass()
+    }
+
     fn prepass_vertex_shader() -> ShaderRef {
         match E::prepass_vertex_shader() {
             ShaderRef::Default => B::prepass_vertex_shader(),

crates/bevy_pbr/src/lib.rs

@@ -223,7 +223,6 @@ impl Plugin for PbrPlugin {
                     debug_flags: self.debug_flags,
                 },
                 MaterialPlugin::<StandardMaterial> {
-                    prepass_enabled: self.prepass_enabled,
                     debug_flags: self.debug_flags,
                     ..Default::default()
                 },

crates/bevy_pbr/src/material.rs

@@ -179,6 +179,19 @@ pub trait Material: Asset + AsBindGroup + Clone + Sized {
         false
     }
 
+    /// Controls if the prepass is enabled for the Material.
+    /// For more information about what a prepass is, see the [`bevy_core_pipeline::prepass`] docs.
+    #[inline]
+    fn enable_prepass() -> bool {
+        true
+    }
+
+    /// Controls if shadows are enabled for the Material.
+    #[inline]
+    fn enable_shadows() -> bool {
+        true
+    }
+
     /// Returns this material's prepass vertex shader. If [`ShaderRef::Default`] is returned, the default prepass vertex shader
     /// will be used.
     ///
@@ -324,14 +337,6 @@ impl Plugin for MaterialsPlugin {
 /// Adds the necessary ECS resources and render logic to enable rendering entities using the given [`Material`]
 /// asset type.
 pub struct MaterialPlugin<M: Material> {
-    /// Controls if the prepass is enabled for the Material.
-    /// For more information about what a prepass is, see the [`bevy_core_pipeline::prepass`] docs.
-    ///
-    /// When it is enabled, it will automatically add the [`PrepassPlugin`]
-    /// required to make the prepass work on this Material.
-    pub prepass_enabled: bool,
-    /// Controls if shadows are enabled for the Material.
-    pub shadows_enabled: bool,
     /// Debugging flags that can optionally be set when constructing the renderer.
     pub debug_flags: RenderDebugFlags,
     pub _marker: PhantomData<M>,
@@ -340,8 +345,6 @@ pub struct MaterialPlugin<M: Material> {
 impl<M: Material> Default for MaterialPlugin<M> {
     fn default() -> Self {
         Self {
-            prepass_enabled: true,
-            shadows_enabled: true,
             debug_flags: RenderDebugFlags::default(),
             _marker: Default::default(),
         }
@@ -366,7 +369,7 @@ where
                     .after(mark_3d_meshes_as_changed_if_their_assets_changed),
             );
 
-        if self.shadows_enabled {
+        if M::enable_shadows() {
             app.add_systems(
                 PostUpdate,
                 check_light_entities_needing_specialization::<M>
@@ -375,13 +378,6 @@ where
         }
 
         if let Some(render_app) = app.get_sub_app_mut(RenderApp) {
-            if self.prepass_enabled {
-                render_app.init_resource::<PrepassEnabled<M>>();
-            }
-            if self.shadows_enabled {
-                render_app.init_resource::<ShadowsEnabled<M>>();
-            }
-
             render_app
                 .add_systems(RenderStartup, add_material_bind_group_allocator::<M>)
                 .add_systems(
@@ -1511,11 +1507,7 @@ where
         SRes<DrawFunctions<AlphaMask3dDeferred>>,
         SRes<DrawFunctions<Shadow>>,
         SRes<AssetServer>,
-        (
-            Option<SRes<ShadowsEnabled<M>>>,
-            Option<SRes<PrepassEnabled<M>>>,
-            M::Param,
-        ),
+        M::Param,
     );
 
     fn prepare_asset(
@@ -1536,13 +1528,13 @@ where
             alpha_mask_deferred_draw_functions,
             shadow_draw_functions,
             asset_server,
-            (shadows_enabled, prepass_enabled, material_param),
+            material_param,
         ): &mut SystemParamItem<Self::Param>,
     ) -> Result<Self::ErasedAsset, PrepareAssetError<Self::SourceAsset>> {
         let material_layout = M::bind_group_layout(render_device);
 
-        let shadows_enabled = shadows_enabled.is_some();
-        let prepass_enabled = prepass_enabled.is_some();
+        let shadows_enabled = M::enable_shadows();
+        let prepass_enabled = M::enable_prepass();
 
         let draw_opaque_pbr = opaque_draw_functions.read().id::<DrawMaterial>();
         let draw_alpha_mask_pbr = alpha_mask_draw_functions.read().id::<DrawMaterial>();
@@ -1811,13 +1803,3 @@ pub fn write_material_bind_group_buffers(
         allocator.write_buffers(&render_device, &render_queue);
     }
 }
-
-/// Marker resource for whether shadows are enabled for this material type
-#[derive(Resource, Debug)]
-pub struct ShadowsEnabled<M: Material>(PhantomData<M>);
-
-impl<M: Material> Default for ShadowsEnabled<M> {
-    fn default() -> Self {
-        Self(PhantomData)
-    }
-}

crates/bevy_pbr/src/prepass/mod.rs

@@ -4,7 +4,7 @@ use crate::{
     alpha_mode_pipeline_key, binding_arrays_are_usable, buffer_layout,
     collect_meshes_for_gpu_building, init_material_pipeline, set_mesh_motion_vector_flags,
     setup_morph_and_skinning_defs, skin, DeferredDrawFunction, DeferredFragmentShader,
-    DeferredVertexShader, DrawMesh, EntitySpecializationTicks, ErasedMaterialPipelineKey, Material,
+    DeferredVertexShader, DrawMesh, EntitySpecializationTicks, ErasedMaterialPipelineKey,
     MaterialPipeline, MaterialProperties, MeshLayouts, MeshPipeline, MeshPipelineKey,
     OpaqueRendererMethod, PreparedMaterial, PrepassDrawFunction, PrepassFragmentShader,
     PrepassVertexShader, RenderLightmaps, RenderMaterialInstances, RenderMeshInstanceFlags,
@@ -61,7 +61,6 @@ use bevy_render::{
     RenderSystems::{PrepareAssets, PrepareResources},
 };
 use bevy_utils::default;
-use core::marker::PhantomData;
 
 /// Sets up everything required to use the prepass pipeline.
 ///
@@ -183,16 +182,6 @@ impl Plugin for PrepassPlugin {
     }
 }
 
-/// Marker resource for whether prepass is enabled globally for this material type
-#[derive(Resource, Debug)]
-pub struct PrepassEnabled<M: Material>(PhantomData<M>);
-
-impl<M: Material> Default for PrepassEnabled<M> {
-    fn default() -> Self {
-        PrepassEnabled(PhantomData)
-    }
-}
-
 #[derive(Resource)]
 struct AnyPrepassPluginLoaded;
 

examples/shader/shader_prepass.rs

@@ -27,12 +27,7 @@ fn main() {
                 ..default()
             }),
             MaterialPlugin::<CustomMaterial>::default(),
-            MaterialPlugin::<PrepassOutputMaterial> {
-                // This material only needs to read the prepass textures,
-                // but the meshes using it should not contribute to the prepass render, so we can disable it.
-                prepass_enabled: false,
-                ..default()
-            },
+            MaterialPlugin::<PrepassOutputMaterial>::default(),
         ))
         .add_systems(Startup, setup)
         .add_systems(Update, (rotate, toggle_prepass_view))
@@ -207,6 +202,10 @@ impl Material for PrepassOutputMaterial {
     fn alpha_mode(&self) -> AlphaMode {
         AlphaMode::Blend
     }
+
+    fn enable_prepass() -> bool {
+        false
+    }
 }
 
 /// Every time you press space, it will cycle between transparent, depth and normals view

release-content/migration-guides/enable_prepass.md

@@ -0,0 +1,25 @@
+---
+title: "`enable_prepass` and `enable_shadows` are now Material methods"
+pull_requests: [20999]
+---
+
+The `MaterialPlugin` fields `prepass_enabled` and `shadows_enabled` have
+been replaced by the `Material` methods `enable_prepass` and `enable_shadows`.
+
+Analogous methods have also been added to `MaterialExtension`
+
+```rust
+/// before
+MaterialPlugin::<MyMaterial> {
+    prepass_enabled: false,
+    shadows_enabled: false,
+}
+
+/// after
+impl Material for MyMaterial {
+    /// ...
+
+    fn enable_prepass() { false }
+    fn enable_shadows() { false }
+}
+```