Add a custom render phase example (#16916)

# Objective

- It's currently very hard for beginners and advanced users to get a
full understanding of a complete render phase.

## Solution

- Implement a full custom render phase
- The render phase in the example is intended to show a custom stencil
phase that renders the stencil in red directly on the screen

---

## Showcase

<img width="1277" alt="image"
src="https://github.com/user-attachments/assets/e9dc0105-4fb6-463f-ad53-0529b575fd28"
/>

## Notes

More docs to explain what is going on is still needed but the example
works and can already help some people.

We might want to consider using a batched phase and cold specialization
in the future, but the example is already complex enough as it is.

---------

Co-authored-by: Christopher Biscardi <chris@christopherbiscardi.com>

Cargo.toml

@@ -518,6 +518,7 @@ http-body-util = "0.1"
 anyhow = "1"
 macro_rules_attribute = "0.2"
 accesskit = "0.17"
+nonmax = "0.5"
 
 [target.'cfg(not(target_family = "wasm"))'.dev-dependencies]
 smol = "2"
@@ -2728,6 +2729,18 @@ description = "A shader that renders a mesh multiple times in one draw call usin
 category = "Shaders"
 wasm = true
 
+[[example]]
+name = "custom_render_phase"
+path = "examples/shader/custom_render_phase.rs"
+doc-scrape-examples = true
+
+[package.metadata.example.custom_render_phase]
+name = "Custom Render Phase"
+description = "Shows how to make a complete render phase"
+category = "Shaders"
+wasm = true
+
+
 [[example]]
 name = "automatic_instancing"
 path = "examples/shader/automatic_instancing.rs"

assets/shaders/custom_stencil.wgsl

@@ -0,0 +1,41 @@
+//! A shader showing how to use the vertex position data to output the 
+//! stencil in the right position
+
+// First we import everything we need from bevy_pbr
+// A 2d shader would be vevry similar but import from bevy_sprite instead
+#import bevy_pbr::{
+    mesh_functions,
+    view_transformations::position_world_to_clip
+}
+
+struct Vertex {
+    // This is needed if you are using batching and/or gpu preprocessing
+    // It's a built in so you don't need to define it in the vertex layout
+    @builtin(instance_index) instance_index: u32,
+    // Like we defined for the vertex layout
+    // position is at location 0
+    @location(0) position: vec3<f32>,
+};
+
+// This is the output of the vertex shader and we also use it as the input for the fragment shader
+struct VertexOutput {
+    @builtin(position) clip_position: vec4<f32>,
+    @location(0) world_position: vec4<f32>,
+};
+
+@vertex
+fn vertex(vertex: Vertex) -> VertexOutput {
+    var out: VertexOutput;
+    // This is how bevy computes the world position
+    // The vertex.instance_index is very important. Especially if you are using batching and gpu preprocessing
+    var world_from_local = mesh_functions::get_world_from_local(vertex.instance_index);
+    out.world_position = mesh_functions::mesh_position_local_to_world(world_from_local, vec4(vertex.position, 1.0));
+    out.clip_position = position_world_to_clip(out.world_position.xyz);
+    return out;
+}
+
+@fragment
+fn fragment(in: VertexOutput) -> @location(0) vec4<f32> {
+    // Output a red color to represent the stencil of the mesh
+    return vec4(1.0, 0.0, 0.0, 1.0);
+}

examples/README.md

@@ -434,6 +434,7 @@ Example | Description
 [Animated](../examples/shader/animate_shader.rs) | A shader that uses dynamic data like the time since startup
 [Array Texture](../examples/shader/array_texture.rs) | A shader that shows how to reuse the core bevy PBR shading functionality in a custom material that obtains the base color from an array texture.
 [Compute - Game of Life](../examples/shader/compute_shader_game_of_life.rs) | A compute shader that simulates Conway's Game of Life
+[Custom Render Phase](../examples/shader/custom_render_phase.rs) | Shows how to make a complete render phase
 [Custom Vertex Attribute](../examples/shader/custom_vertex_attribute.rs) | A shader that reads a mesh's custom vertex attribute
 [Custom phase item](../examples/shader/custom_phase_item.rs) | Demonstrates how to enqueue custom draw commands in a render phase
 [Extended Material](../examples/shader/extended_material.rs) | A custom shader that builds on the standard material

examples/shader/custom_render_phase.rs

@@ -0,0 +1,629 @@
+//! This example demonstrates how to write a custom phase
+//!
+//! Render phases in bevy are used whenever you need to draw a group of meshes in a specific way.
+//! For example, bevy's main pass has an opaque phase, a transparent phase for both 2d and 3d.
+//! Sometimes, you may want to only draw a subset of meshes before or after the builtin phase. In
+//! those situations you need to write your own phase.
+//!
+//! This example showcases how writing a custom phase to draw a stencil of a bevy mesh could look
+//! like. Some shortcuts have been used for simplicity.
+//!
+//! This example was made for 3d, but a 2d equivalent would be almost identical.
+
+use std::ops::Range;
+
+use bevy::{
+    core_pipeline::core_3d::graph::{Core3d, Node3d},
+    ecs::{
+        query::QueryItem,
+        system::{lifetimeless::SRes, SystemParamItem},
+    },
+    math::FloatOrd,
+    pbr::{
+        DrawMesh, MeshInputUniform, MeshPipeline, MeshPipelineKey, MeshPipelineViewLayoutKey,
+        MeshUniform, RenderMeshInstances, SetMeshBindGroup, SetMeshViewBindGroup,
+    },
+    platform_support::collections::HashSet,
+    prelude::*,
+    render::{
+        batching::{
+            gpu_preprocessing::{
+                batch_and_prepare_sorted_render_phase, IndirectParametersMetadata,
+            },
+            GetBatchData, GetFullBatchData,
+        },
+        camera::ExtractedCamera,
+        extract_component::{ExtractComponent, ExtractComponentPlugin},
+        mesh::{allocator::MeshAllocator, MeshVertexBufferLayoutRef, RenderMesh},
+        render_asset::RenderAssets,
+        render_graph::{
+            NodeRunError, RenderGraphApp, RenderGraphContext, RenderLabel, ViewNode, ViewNodeRunner,
+        },
+        render_phase::{
+            sort_phase_system, AddRenderCommand, CachedRenderPipelinePhaseItem, DrawFunctionId,
+            DrawFunctions, PhaseItem, PhaseItemExtraIndex, SetItemPipeline, SortedPhaseItem,
+            ViewSortedRenderPhases,
+        },
+        render_resource::{
+            CachedRenderPipelineId, ColorTargetState, ColorWrites, Face, FragmentState, FrontFace,
+            MultisampleState, PipelineCache, PolygonMode, PrimitiveState, RenderPassDescriptor,
+            RenderPipelineDescriptor, SpecializedMeshPipeline, SpecializedMeshPipelineError,
+            SpecializedMeshPipelines, TextureFormat, VertexState,
+        },
+        renderer::RenderContext,
+        sync_world::MainEntity,
+        view::{ExtractedView, RenderVisibleEntities, RetainedViewEntity, ViewTarget},
+        Extract, Render, RenderApp, RenderSet,
+    },
+};
+use nonmax::NonMaxU32;
+
+const SHADER_ASSET_PATH: &str = "shaders/custom_stencil.wgsl";
+
+fn main() {
+    App::new()
+        .add_plugins((DefaultPlugins, MeshStencilPhasePlugin))
+        .add_systems(Startup, setup)
+        .run();
+}
+
+fn setup(
+    mut commands: Commands,
+    mut meshes: ResMut<Assets<Mesh>>,
+    mut materials: ResMut<Assets<StandardMaterial>>,
+) {
+    // circular base
+    commands.spawn((
+        Mesh3d(meshes.add(Circle::new(4.0))),
+        MeshMaterial3d(materials.add(Color::WHITE)),
+        Transform::from_rotation(Quat::from_rotation_x(-std::f32::consts::FRAC_PI_2)),
+    ));
+    // cube
+    // This cube will be rendered by the main pass, but it will also be rendered by our custom
+    // pass. This should result in an unlit red cube
+    commands.spawn((
+        Mesh3d(meshes.add(Cuboid::new(1.0, 1.0, 1.0))),
+        MeshMaterial3d(materials.add(Color::srgb_u8(124, 144, 255))),
+        Transform::from_xyz(0.0, 0.5, 0.0),
+        // This marker component is used to identify which mesh will be used in our custom pass
+        // The circle doesn't have it so it won't be rendered in our pass
+        DrawStencil,
+    ));
+    // light
+    commands.spawn((
+        PointLight {
+            shadows_enabled: true,
+            ..default()
+        },
+        Transform::from_xyz(4.0, 8.0, 4.0),
+    ));
+    // camera
+    commands.spawn((
+        Camera3d::default(),
+        Transform::from_xyz(-2.0, 4.5, 9.0).looking_at(Vec3::ZERO, Vec3::Y),
+        // disable msaa for simplicity
+        Msaa::Off,
+    ));
+}
+
+#[derive(Component, ExtractComponent, Clone, Copy, Default)]
+struct DrawStencil;
+
+struct MeshStencilPhasePlugin;
+impl Plugin for MeshStencilPhasePlugin {
+    fn build(&self, app: &mut App) {
+        app.add_plugins((ExtractComponentPlugin::<DrawStencil>::default(),));
+        // We need to get the render app from the main app
+        let Some(render_app) = app.get_sub_app_mut(RenderApp) else {
+            return;
+        };
+        render_app
+            .init_resource::<SpecializedMeshPipelines<StencilPipeline>>()
+            .init_resource::<DrawFunctions<Stencil3d>>()
+            .add_render_command::<Stencil3d, DrawMesh3dStencil>()
+            .init_resource::<ViewSortedRenderPhases<Stencil3d>>()
+            .add_systems(ExtractSchedule, extract_camera_phases)
+            .add_systems(
+                Render,
+                (
+                    queue_custom_meshes.in_set(RenderSet::QueueMeshes),
+                    sort_phase_system::<Stencil3d>.in_set(RenderSet::PhaseSort),
+                    batch_and_prepare_sorted_render_phase::<Stencil3d, StencilPipeline>
+                        .in_set(RenderSet::PrepareResources),
+                ),
+            );
+
+        render_app
+            .add_render_graph_node::<ViewNodeRunner<CustomDrawNode>>(Core3d, CustomDrawPassLabel)
+            // Tell the node to run after the main pass
+            .add_render_graph_edges(Core3d, (Node3d::MainOpaquePass, CustomDrawPassLabel));
+    }
+
+    fn finish(&self, app: &mut App) {
+        // We need to get the render app from the main app
+        let Some(render_app) = app.get_sub_app_mut(RenderApp) else {
+            return;
+        };
+        // The pipeline needs the RenderDevice to be created and it's only available once plugins
+        // are initialized
+        render_app.init_resource::<StencilPipeline>();
+    }
+}
+
+#[derive(Resource)]
+struct StencilPipeline {
+    /// The base mesh pipeline defined by bevy
+    ///
+    /// Since we want to draw a stencil of an existing bevy mesh we want to reuse the default
+    /// pipeline as much as possible
+    mesh_pipeline: MeshPipeline,
+    /// Stores the shader used for this pipeline directly on the pipeline.
+    /// This isn't required, it's only done like this for simplicity.
+    shader_handle: Handle<Shader>,
+}
+impl FromWorld for StencilPipeline {
+    fn from_world(world: &mut World) -> Self {
+        Self {
+            mesh_pipeline: MeshPipeline::from_world(world),
+            shader_handle: world.resource::<AssetServer>().load(SHADER_ASSET_PATH),
+        }
+    }
+}
+
+// For more information on how SpecializedMeshPipeline work, please look at the
+// specialized_mesh_pipeline example
+impl SpecializedMeshPipeline for StencilPipeline {
+    type Key = MeshPipelineKey;
+
+    fn specialize(
+        &self,
+        key: Self::Key,
+        layout: &MeshVertexBufferLayoutRef,
+    ) -> Result<RenderPipelineDescriptor, SpecializedMeshPipelineError> {
+        // We will only use the position of the mesh in our shader so we only need to specify that
+        let mut vertex_attributes = Vec::new();
+        if layout.0.contains(Mesh::ATTRIBUTE_POSITION) {
+            // Make sure this matches the shader location
+            vertex_attributes.push(Mesh::ATTRIBUTE_POSITION.at_shader_location(0));
+        }
+        // This will automatically generate the correct `VertexBufferLayout` based on the vertex attributes
+        let vertex_buffer_layout = layout.0.get_layout(&vertex_attributes)?;
+
+        Ok(RenderPipelineDescriptor {
+            label: Some("Specialized Mesh Pipeline".into()),
+            // We want to reuse the data from bevy so we use the same bind groups as the default
+            // mesh pipeline
+            layout: vec![
+                // Bind group 0 is the view uniform
+                self.mesh_pipeline
+                    .get_view_layout(MeshPipelineViewLayoutKey::from(key))
+                    .clone(),
+                // Bind group 1 is the mesh uniform
+                self.mesh_pipeline.mesh_layouts.model_only.clone(),
+            ],
+            push_constant_ranges: vec![],
+            vertex: VertexState {
+                shader: self.shader_handle.clone(),
+                shader_defs: vec![],
+                entry_point: "vertex".into(),
+                buffers: vec![vertex_buffer_layout],
+            },
+            fragment: Some(FragmentState {
+                shader: self.shader_handle.clone(),
+                shader_defs: vec![],
+                entry_point: "fragment".into(),
+                targets: vec![Some(ColorTargetState {
+                    format: TextureFormat::bevy_default(),
+                    blend: None,
+                    write_mask: ColorWrites::ALL,
+                })],
+            }),
+            primitive: PrimitiveState {
+                topology: key.primitive_topology(),
+                front_face: FrontFace::Ccw,
+                cull_mode: Some(Face::Back),
+                polygon_mode: PolygonMode::Fill,
+                ..default()
+            },
+            depth_stencil: None,
+            // It's generally recommended to specialize your pipeline for MSAA,
+            // but it's not always possible
+            multisample: MultisampleState::default(),
+            zero_initialize_workgroup_memory: false,
+        })
+    }
+}
+
+// We will reuse render commands already defined by bevy to draw a 3d mesh
+type DrawMesh3dStencil = (
+    SetItemPipeline,
+    // This will set the view bindings in group 0
+    SetMeshViewBindGroup<0>,
+    // This will set the mesh bindings in group 1
+    SetMeshBindGroup<1>,
+    // This will draw the mesh
+    DrawMesh,
+);
+
+// This is the data required per entity drawn in a custom phase in bevy. More specifically this is the
+// data required when using a ViewSortedRenderPhase. This would look differently if we wanted a
+// batched render phase. Sorted phases are a bit easier to implement, but a batched phase would
+// look similar.
+//
+// If you want to see how a batched phase implementation looks, you should look at the Opaque2d
+// phase.
+struct Stencil3d {
+    pub sort_key: FloatOrd,
+    pub entity: (Entity, MainEntity),
+    pub pipeline: CachedRenderPipelineId,
+    pub draw_function: DrawFunctionId,
+    pub batch_range: Range<u32>,
+    pub extra_index: PhaseItemExtraIndex,
+    /// Whether the mesh in question is indexed (uses an index buffer in
+    /// addition to its vertex buffer).
+    pub indexed: bool,
+}
+
+// For more information about writing a phase item, please look at the custom_phase_item example
+impl PhaseItem for Stencil3d {
+    #[inline]
+    fn entity(&self) -> Entity {
+        self.entity.0
+    }
+
+    #[inline]
+    fn main_entity(&self) -> MainEntity {
+        self.entity.1
+    }
+
+    #[inline]
+    fn draw_function(&self) -> DrawFunctionId {
+        self.draw_function
+    }
+
+    #[inline]
+    fn batch_range(&self) -> &Range<u32> {
+        &self.batch_range
+    }
+
+    #[inline]
+    fn batch_range_mut(&mut self) -> &mut Range<u32> {
+        &mut self.batch_range
+    }
+
+    #[inline]
+    fn extra_index(&self) -> PhaseItemExtraIndex {
+        self.extra_index.clone()
+    }
+
+    #[inline]
+    fn batch_range_and_extra_index_mut(&mut self) -> (&mut Range<u32>, &mut PhaseItemExtraIndex) {
+        (&mut self.batch_range, &mut self.extra_index)
+    }
+}
+
+impl SortedPhaseItem for Stencil3d {
+    type SortKey = FloatOrd;
+
+    #[inline]
+    fn sort_key(&self) -> Self::SortKey {
+        self.sort_key
+    }
+
+    #[inline]
+    fn sort(items: &mut [Self]) {
+        // bevy normally uses radsort instead of the std slice::sort_by_key
+        // radsort is a stable radix sort that performed better than `slice::sort_by_key` or `slice::sort_unstable_by_key`.
+        // Since it is not re-exported by bevy, we just use the std sort for the purpose of the example
+        items.sort_by_key(SortedPhaseItem::sort_key);
+    }
+
+    #[inline]
+    fn indexed(&self) -> bool {
+        self.indexed
+    }
+}
+
+impl CachedRenderPipelinePhaseItem for Stencil3d {
+    #[inline]
+    fn cached_pipeline(&self) -> CachedRenderPipelineId {
+        self.pipeline
+    }
+}
+
+impl GetBatchData for StencilPipeline {
+    type Param = (
+        SRes<RenderMeshInstances>,
+        SRes<RenderAssets<RenderMesh>>,
+        SRes<MeshAllocator>,
+    );
+    type CompareData = AssetId<Mesh>;
+    type BufferData = MeshUniform;
+
+    fn get_batch_data(
+        (mesh_instances, _render_assets, mesh_allocator): &SystemParamItem<Self::Param>,
+        (_entity, main_entity): (Entity, MainEntity),
+    ) -> Option<(Self::BufferData, Option<Self::CompareData>)> {
+        let RenderMeshInstances::CpuBuilding(ref mesh_instances) = **mesh_instances else {
+            error!(
+                "`get_batch_data` should never be called in GPU mesh uniform \
+                building mode"
+            );
+            return None;
+        };
+        let mesh_instance = mesh_instances.get(&main_entity)?;
+        let first_vertex_index =
+            match mesh_allocator.mesh_vertex_slice(&mesh_instance.mesh_asset_id) {
+                Some(mesh_vertex_slice) => mesh_vertex_slice.range.start,
+                None => 0,
+            };
+        let mesh_uniform = {
+            let mesh_transforms = &mesh_instance.transforms;
+            let (local_from_world_transpose_a, local_from_world_transpose_b) =
+                mesh_transforms.world_from_local.inverse_transpose_3x3();
+            MeshUniform {
+                world_from_local: mesh_transforms.world_from_local.to_transpose(),
+                previous_world_from_local: mesh_transforms.previous_world_from_local.to_transpose(),
+                lightmap_uv_rect: UVec2::ZERO,
+                local_from_world_transpose_a,
+                local_from_world_transpose_b,
+                flags: mesh_transforms.flags,
+                first_vertex_index,
+                current_skin_index: u32::MAX,
+                previous_skin_index: u32::MAX,
+                material_and_lightmap_bind_group_slot: 0,
+            }
+        };
+        Some((mesh_uniform, None))
+    }
+}
+impl GetFullBatchData for StencilPipeline {
+    type BufferInputData = MeshInputUniform;
+
+    fn get_index_and_compare_data(
+        (mesh_instances, _, _): &SystemParamItem<Self::Param>,
+        main_entity: MainEntity,
+    ) -> Option<(NonMaxU32, Option<Self::CompareData>)> {
+        // This should only be called during GPU building.
+        let RenderMeshInstances::GpuBuilding(ref mesh_instances) = **mesh_instances else {
+            error!(
+                "`get_index_and_compare_data` should never be called in CPU mesh uniform building \
+                mode"
+            );
+            return None;
+        };
+        let mesh_instance = mesh_instances.get(&main_entity)?;
+        Some((
+            mesh_instance.current_uniform_index,
+            mesh_instance
+                .should_batch()
+                .then_some(mesh_instance.mesh_asset_id),
+        ))
+    }
+
+    fn get_binned_batch_data(
+        (mesh_instances, _render_assets, mesh_allocator): &SystemParamItem<Self::Param>,
+        main_entity: MainEntity,
+    ) -> Option<Self::BufferData> {
+        let RenderMeshInstances::CpuBuilding(ref mesh_instances) = **mesh_instances else {
+            error!(
+                "`get_binned_batch_data` should never be called in GPU mesh uniform building mode"
+            );
+            return None;
+        };
+        let mesh_instance = mesh_instances.get(&main_entity)?;
+        let first_vertex_index =
+            match mesh_allocator.mesh_vertex_slice(&mesh_instance.mesh_asset_id) {
+                Some(mesh_vertex_slice) => mesh_vertex_slice.range.start,
+                None => 0,
+            };
+
+        Some(MeshUniform::new(
+            &mesh_instance.transforms,
+            first_vertex_index,
+            mesh_instance.material_bindings_index.slot,
+            None,
+            None,
+            None,
+        ))
+    }
+
+    fn write_batch_indirect_parameters_metadata(
+        mesh_index: u32,
+        indexed: bool,
+        base_output_index: u32,
+        batch_set_index: Option<NonMaxU32>,
+        indirect_parameters_buffers: &mut bevy_render::batching::gpu_preprocessing::IndirectParametersBuffers,
+        indirect_parameters_offset: u32,
+    ) {
+        // Note that `IndirectParameters` covers both of these structures, even
+        // though they actually have distinct layouts. See the comment above that
+        // type for more information.
+        let indirect_parameters = IndirectParametersMetadata {
+            mesh_index,
+            base_output_index,
+            batch_set_index: match batch_set_index {
+                None => !0,
+                Some(batch_set_index) => u32::from(batch_set_index),
+            },
+            early_instance_count: 0,
+            late_instance_count: 0,
+        };
+
+        if indexed {
+            indirect_parameters_buffers
+                .set_indexed(indirect_parameters_offset, indirect_parameters);
+        } else {
+            indirect_parameters_buffers
+                .set_non_indexed(indirect_parameters_offset, indirect_parameters);
+        }
+    }
+
+    fn get_binned_index(
+        _param: &SystemParamItem<Self::Param>,
+        _query_item: MainEntity,
+    ) -> Option<NonMaxU32> {
+        None
+    }
+}
+
+// When defining a phase, we need to extract it from the main world and add it to a resource
+// that will be used by the render world. We need to give that resource all views that will use
+// that phase
+fn extract_camera_phases(
+    mut stencil_phases: ResMut<ViewSortedRenderPhases<Stencil3d>>,
+    cameras: Extract<Query<(Entity, &Camera), With<Camera3d>>>,
+    mut live_entities: Local<HashSet<RetainedViewEntity>>,
+) {
+    live_entities.clear();
+    for (main_entity, camera) in &cameras {
+        if !camera.is_active {
+            continue;
+        }
+        // This is the main camera, so we use the first subview index (0)
+        let retained_view_entity = RetainedViewEntity::new(main_entity.into(), None, 0);
+
+        stencil_phases.insert_or_clear(retained_view_entity);
+        live_entities.insert(retained_view_entity);
+    }
+
+    // Clear out all dead views.
+    stencil_phases.retain(|camera_entity, _| live_entities.contains(camera_entity));
+}
+
+// This is a very important step when writing a custom phase.
+//
+// This system determines which meshes will be added to the phase.
+fn queue_custom_meshes(
+    custom_draw_functions: Res<DrawFunctions<Stencil3d>>,
+    mut pipelines: ResMut<SpecializedMeshPipelines<StencilPipeline>>,
+    pipeline_cache: Res<PipelineCache>,
+    custom_draw_pipeline: Res<StencilPipeline>,
+    render_meshes: Res<RenderAssets<RenderMesh>>,
+    render_mesh_instances: Res<RenderMeshInstances>,
+    mut custom_render_phases: ResMut<ViewSortedRenderPhases<Stencil3d>>,
+    mut views: Query<(&ExtractedView, &RenderVisibleEntities, &Msaa)>,
+    has_marker: Query<(), With<DrawStencil>>,
+) {
+    for (view, visible_entities, msaa) in &mut views {
+        let Some(custom_phase) = custom_render_phases.get_mut(&view.retained_view_entity) else {
+            continue;
+        };
+        let draw_custom = custom_draw_functions.read().id::<DrawMesh3dStencil>();
+
+        // Create the key based on the view.
+        // In this case we only care about MSAA and HDR
+        let view_key = MeshPipelineKey::from_msaa_samples(msaa.samples())
+            | MeshPipelineKey::from_hdr(view.hdr);
+
+        let rangefinder = view.rangefinder3d();
+        // Since our phase can work on any 3d mesh we can reuse the default mesh 3d filter
+        for (render_entity, visible_entity) in visible_entities.iter::<Mesh3d>() {
+            // We only want meshes with the marker component to be queued to our phase.
+            if has_marker.get(*render_entity).is_err() {
+                continue;
+            }
+            let Some(mesh_instance) = render_mesh_instances.render_mesh_queue_data(*visible_entity)
+            else {
+                continue;
+            };
+            let Some(mesh) = render_meshes.get(mesh_instance.mesh_asset_id) else {
+                continue;
+            };
+
+            // Specialize the key for the current mesh entity
+            // For this example we only specialize based on the mesh topology
+            // but you could have more complex keys and that's where you'd need to create those keys
+            let mut mesh_key = view_key;
+            mesh_key |= MeshPipelineKey::from_primitive_topology(mesh.primitive_topology());
+
+            let pipeline_id = pipelines.specialize(
+                &pipeline_cache,
+                &custom_draw_pipeline,
+                mesh_key,
+                &mesh.layout,
+            );
+            let pipeline_id = match pipeline_id {
+                Ok(id) => id,
+                Err(err) => {
+                    error!("{}", err);
+                    continue;
+                }
+            };
+            let distance = rangefinder.distance_translation(&mesh_instance.translation);
+            // At this point we have all the data we need to create a phase item and add it to our
+            // phase
+            custom_phase.add(Stencil3d {
+                // Sort the data based on the distance to the view
+                sort_key: FloatOrd(distance),
+                entity: (*render_entity, *visible_entity),
+                pipeline: pipeline_id,
+                draw_function: draw_custom,
+                // Sorted phase items aren't batched
+                batch_range: 0..1,
+                extra_index: PhaseItemExtraIndex::None,
+                indexed: mesh.indexed(),
+            });
+        }
+    }
+}
+
+// Render label used to order our render graph node that will render our phase
+#[derive(RenderLabel, Debug, Clone, Hash, PartialEq, Eq)]
+struct CustomDrawPassLabel;
+
+#[derive(Default)]
+struct CustomDrawNode;
+impl ViewNode for CustomDrawNode {
+    type ViewQuery = (
+        &'static ExtractedCamera,
+        &'static ExtractedView,
+        &'static ViewTarget,
+    );
+
+    fn run<'w>(
+        &self,
+        graph: &mut RenderGraphContext,
+        render_context: &mut RenderContext<'w>,
+        (camera, view, target): QueryItem<'w, Self::ViewQuery>,
+        world: &'w World,
+    ) -> Result<(), NodeRunError> {
+        // First, we need to get our phases resource
+        let Some(stencil_phases) = world.get_resource::<ViewSortedRenderPhases<Stencil3d>>() else {
+            return Ok(());
+        };
+
+        // Get the view entity from the graph
+        let view_entity = graph.view_entity();
+
+        // Get the phase for the current view running our node
+        let Some(stencil_phase) = stencil_phases.get(&view.retained_view_entity) else {
+            return Ok(());
+        };
+
+        // Render pass setup
+        let mut render_pass = render_context.begin_tracked_render_pass(RenderPassDescriptor {
+            label: Some("stencil pass"),
+            // For the purpose of the example, we will write directly to the view target. A real
+            // stencil pass would write to a custom texture and that texture would be used in later
+            // passes to render custom effects using it.
+            color_attachments: &[Some(target.get_color_attachment())],
+            // We don't bind any depth buffer for this pass
+            depth_stencil_attachment: None,
+            timestamp_writes: None,
+            occlusion_query_set: None,
+        });
+
+        if let Some(viewport) = camera.viewport.as_ref() {
+            render_pass.set_camera_viewport(viewport);
+        }
+
+        // Render the phase
+        // This will execute each draw functions of each phase items queued in this phase
+        if let Err(err) = stencil_phase.render(&mut render_pass, world, view_entity) {
+            error!("Error encountered while rendering the stencil phase {err:?}");
+        }
+
+        Ok(())
+    }
+}