Try #6284:

Cargo.toml

@@ -1220,6 +1220,17 @@ description = "A shader and a material that uses it"
 category = "Shaders"
 wasm = true
 
+[[example]]
+name = "shader_prepass"
+path = "examples/shader/shader_prepass.rs"
+
+[package.metadata.example.shader_prepass]
+name = "Material Prepass"
+description = "A shader that uses the depth texture generated in a prepass"
+category = "Shaders"
+wasm = false
+
+
 [[example]]
 name = "shader_material_screenspace_texture"
 path = "examples/shader/shader_material_screenspace_texture.rs"

assets/shaders/show_prepass.wgsl

@@ -0,0 +1,26 @@
+#import bevy_pbr::mesh_types
+#import bevy_pbr::mesh_view_bindings
+#import bevy_pbr::utils
+
+@group(1) @binding(0)
+var<uniform> show_depth: f32;
+@group(1) @binding(1)
+var<uniform> show_normal: f32;
+
+@fragment
+fn fragment(
+    @builtin(position) frag_coord: vec4<f32>,
+    @builtin(sample_index) sample_index: u32,
+    #import bevy_pbr::mesh_vertex_output
+) -> @location(0) vec4<f32> {
+    if show_depth == 1.0 {
+        let depth = prepass_depth(frag_coord, sample_index);
+        return vec4(depth, depth, depth, 1.0);
+    } else if show_normal == 1.0 {
+        let normal = prepass_normal(frag_coord, sample_index);
+        return vec4(normal, 1.0);
+    } else {
+        // transparent
+        return vec4(0.0);
+    }
+}

crates/bevy_core_pipeline/src/core_3d/main_pass_3d_node.rs

@@ -1,6 +1,7 @@
 use crate::{
     clear_color::{ClearColor, ClearColorConfig},
     core_3d::{AlphaMask3d, Camera3d, Opaque3d, Transparent3d},
+    prepass::{DepthPrepass, NormalPrepass},
 };
 use bevy_ecs::prelude::*;
 use bevy_render::{
@@ -14,6 +15,8 @@ use bevy_render::{
 #[cfg(feature = "trace")]
 use bevy_utils::tracing::info_span;
 
+use super::Camera3dDepthLoadOp;
+
 pub struct MainPass3dNode {
     query: QueryState<
         (
@@ -24,6 +27,8 @@ pub struct MainPass3dNode {
             &'static Camera3d,
             &'static ViewTarget,
             &'static ViewDepthTexture,
+            Option<&'static DepthPrepass>,
+            Option<&'static NormalPrepass>,
         ),
         With<ExtractedView>,
     >,
@@ -55,13 +60,20 @@ impl Node for MainPass3dNode {
         world: &World,
     ) -> Result<(), NodeRunError> {
         let view_entity = graph.get_input_entity(Self::IN_VIEW)?;
-        let (camera, opaque_phase, alpha_mask_phase, transparent_phase, camera_3d, target, depth) =
-            match self.query.get_manual(world, view_entity) {
-                Ok(query) => query,
-                Err(_) => {
-                    return Ok(());
-                } // No window
-            };
+        let Ok((
+            camera,
+            opaque_phase,
+            alpha_mask_phase,
+            transparent_phase,
+            camera_3d,
+            target,
+            depth,
+            depth_prepass,
+            normal_prepass,
+        )) = self.query.get_manual(world, view_entity) else {
+            // No window
+            return Ok(());
+        };
 
         // Always run opaque pass to ensure screen is cleared
         {
@@ -88,8 +100,15 @@ impl Node for MainPass3dNode {
                     view: &depth.view,
                     // NOTE: The opaque main pass loads the depth buffer and possibly overwrites it
                     depth_ops: Some(Operations {
-                        // NOTE: 0.0 is the far plane due to bevy's use of reverse-z projections.
-                        load: camera_3d.depth_load_op.clone().into(),
+                        load: if depth_prepass.is_some() || normal_prepass.is_some() {
+                            // if any prepass runs, it will generate a depth buffer so we should use it,
+                            // even if only the normal_prepass is used.
+                            Camera3dDepthLoadOp::Load
+                        } else {
+                            // NOTE: 0.0 is the far plane due to bevy's use of reverse-z projections.
+                            camera_3d.depth_load_op.clone()
+                        }
+                        .into(),
                         store: true,
                     }),
                     stencil_ops: None,

crates/bevy_core_pipeline/src/core_3d/mod.rs

@@ -7,6 +7,7 @@ pub mod graph {
         pub const VIEW_ENTITY: &str = "view_entity";
     }
     pub mod node {
+        pub const PREPASS: &str = "prepass";
         pub const MAIN_PASS: &str = "main_pass";
         pub const BLOOM: &str = "bloom";
         pub const TONEMAPPING: &str = "tonemapping";
@@ -43,7 +44,11 @@ use bevy_render::{
 };
 use bevy_utils::{FloatOrd, HashMap};
 
-use crate::{tonemapping::TonemappingNode, upscaling::UpscalingNode};
+use crate::{
+    prepass::{node::PrepassNode, DepthPrepass},
+    tonemapping::TonemappingNode,
+    upscaling::UpscalingNode,
+};
 
 pub struct Core3dPlugin;
 
@@ -68,20 +73,29 @@ impl Plugin for Core3dPlugin {
             .add_system_to_stage(RenderStage::PhaseSort, sort_phase_system::<AlphaMask3d>)
             .add_system_to_stage(RenderStage::PhaseSort, sort_phase_system::<Transparent3d>);
 
+        let prepass_node = PrepassNode::new(&mut render_app.world);
         let pass_node_3d = MainPass3dNode::new(&mut render_app.world);
         let tonemapping = TonemappingNode::new(&mut render_app.world);
         let upscaling = UpscalingNode::new(&mut render_app.world);
         let mut graph = render_app.world.resource_mut::<RenderGraph>();
 
         let mut draw_3d_graph = RenderGraph::default();
+        draw_3d_graph.add_node(graph::node::PREPASS, prepass_node);
         draw_3d_graph.add_node(graph::node::MAIN_PASS, pass_node_3d);
         draw_3d_graph.add_node(graph::node::TONEMAPPING, tonemapping);
         draw_3d_graph.add_node(graph::node::END_MAIN_PASS_POST_PROCESSING, EmptyNode);
         draw_3d_graph.add_node(graph::node::UPSCALING, upscaling);
+
         let input_node_id = draw_3d_graph.set_input(vec![SlotInfo::new(
             graph::input::VIEW_ENTITY,
             SlotType::Entity,
         )]);
+        draw_3d_graph.add_slot_edge(
+            input_node_id,
+            graph::input::VIEW_ENTITY,
+            graph::node::PREPASS,
+            PrepassNode::IN_VIEW,
+        );
         draw_3d_graph.add_slot_edge(
             input_node_id,
             graph::input::VIEW_ENTITY,
@@ -100,6 +114,7 @@ impl Plugin for Core3dPlugin {
             graph::node::UPSCALING,
             UpscalingNode::IN_VIEW,
         );
+        draw_3d_graph.add_node_edge(graph::node::PREPASS, graph::node::MAIN_PASS);
         draw_3d_graph.add_node_edge(graph::node::MAIN_PASS, graph::node::TONEMAPPING);
         draw_3d_graph.add_node_edge(
             graph::node::TONEMAPPING,
@@ -253,7 +268,7 @@ pub fn prepare_core_3d_depth_textures(
     msaa: Res<Msaa>,
     render_device: Res<RenderDevice>,
     views_3d: Query<
-        (Entity, &ExtractedCamera),
+        (Entity, &ExtractedCamera, Option<&DepthPrepass>),
         (
             With<RenderPhase<Opaque3d>>,
             With<RenderPhase<AlphaMask3d>>,
@@ -262,34 +277,46 @@ pub fn prepare_core_3d_depth_textures(
     >,
 ) {
     let mut textures = HashMap::default();
-    for (entity, camera) in &views_3d {
-        if let Some(physical_target_size) = camera.physical_target_size {
-            let cached_texture = textures
-                .entry(camera.target.clone())
-                .or_insert_with(|| {
-                    texture_cache.get(
-                        &render_device,
-                        TextureDescriptor {
-                            label: Some("view_depth_texture"),
-                            size: Extent3d {
-                                depth_or_array_layers: 1,
-                                width: physical_target_size.x,
-                                height: physical_target_size.y,
-                            },
-                            mip_level_count: 1,
-                            sample_count: msaa.samples,
-                            dimension: TextureDimension::D2,
-                            format: TextureFormat::Depth32Float, /* PERF: vulkan docs recommend using 24
-                                                                  * bit depth for better performance */
-                            usage: TextureUsages::RENDER_ATTACHMENT,
-                        },
-                    )
-                })
-                .clone();
-            commands.entity(entity).insert(ViewDepthTexture {
-                texture: cached_texture.texture,
-                view: cached_texture.default_view,
-            });
-        }
+    for (entity, camera, depth_prepass) in &views_3d {
+        let Some(physical_target_size) = camera.physical_target_size else {
+            continue;
+        };
+
+        let cached_texture = textures
+            .entry(camera.target.clone())
+            .or_insert_with(|| {
+                // Default usage required to write to the depth texture
+                let mut usage = TextureUsages::RENDER_ATTACHMENT;
+                if depth_prepass.is_some() {
+                    // Required to read the output of the prepass
+                    usage |= TextureUsages::COPY_SRC;
+                }
+
+                // The size of the depth texture
+                let size = Extent3d {
+                    depth_or_array_layers: 1,
+                    width: physical_target_size.x,
+                    height: physical_target_size.y,
+                };
+
+                let descriptor = TextureDescriptor {
+                    label: Some("view_depth_texture"),
+                    size,
+                    mip_level_count: 1,
+                    sample_count: msaa.samples,
+                    dimension: TextureDimension::D2,
+                    // PERF: vulkan docs recommend using 24 bit depth for better performance
+                    format: TextureFormat::Depth32Float,
+                    usage,
+                };
+
+                texture_cache.get(&render_device, descriptor)
+            })
+            .clone();
+
+        commands.entity(entity).insert(ViewDepthTexture {
+            texture: cached_texture.texture,
+            view: cached_texture.default_view,
+        });
     }
 }

crates/bevy_core_pipeline/src/lib.rs

@@ -4,6 +4,7 @@ pub mod core_2d;
 pub mod core_3d;
 pub mod fullscreen_vertex_shader;
 pub mod fxaa;
+pub mod prepass;
 pub mod tonemapping;
 pub mod upscaling;
 
@@ -23,6 +24,7 @@ use crate::{
     core_3d::Core3dPlugin,
     fullscreen_vertex_shader::FULLSCREEN_SHADER_HANDLE,
     fxaa::FxaaPlugin,
+    prepass::{DepthPrepass, NormalPrepass},
     tonemapping::TonemappingPlugin,
     upscaling::UpscalingPlugin,
 };
@@ -44,6 +46,8 @@ impl Plugin for CorePipelinePlugin {
 
         app.register_type::<ClearColor>()
             .register_type::<ClearColorConfig>()
+            .register_type::<DepthPrepass>()
+            .register_type::<NormalPrepass>()
             .init_resource::<ClearColor>()
             .add_plugin(ExtractResourcePlugin::<ClearColor>::default())
             .add_plugin(Core2dPlugin)