Add RenderGraphApp to simplify adding render nodes (#8007)

# Objective

- Adding a node to the render_graph can be quite verbose and error prone
because there's a lot of moving parts to it.

## Solution

- Encapsulate this in a simple utility method
	- Mostly intended for optional nodes that have specific ordering
- Requires that the `Node` impl `FromWorld`, but every internal node is
built using a new function taking a `&mut World` so it was essentially
already `FromWorld`
- Use it for the bloom, fxaa and taa, nodes. 
- The main nodes don't use it because they rely more on the order of
many nodes being added

---

## Changelog

- Impl `FromWorld` for `BloomNode`, `FxaaNode` and `TaaNode`
- Added `RenderGraph::add_node_edges()`
- Added `RenderGraph::sub_graph()`
- Added `RenderGraph::sub_graph_mut()`
- Added `RenderGraphApp`, `RenderGraphApp::add_render_graph_node`,
`RenderGraphApp::add_render_graph_edges`,
`RenderGraphApp::add_render_graph_edge`

## Notes

~~This was taken out of https://github.com/bevyengine/bevy/pull/7995
because it works on it's own. Once the linked PR is done, the new
`add_node()` will be simplified a bit since the input/output params
won't be necessary.~~

This feature will be useful in most of the upcoming render nodes so it's
impact will be more relevant at that point.

Partially fixes #7985 

## Future work

* Add a way to automatically label nodes or at least make it part of the
trait. This would remove one more field from the functions added in this
PR
* Use it in the main pass 2d/3d

---------

Co-authored-by: Carter Anderson <mcanders1@gmail.com>

crates/bevy_core_pipeline/src/bloom/mod.rs

@@ -16,7 +16,7 @@ use bevy_render::{
         ComponentUniforms, DynamicUniformIndex, ExtractComponentPlugin, UniformComponentPlugin,
     },
     prelude::Color,
-    render_graph::{Node, NodeRunError, RenderGraph, RenderGraphContext},
+    render_graph::{Node, NodeRunError, RenderGraphApp, RenderGraphContext},
     render_resource::*,
     renderer::{RenderContext, RenderDevice},
     texture::{CachedTexture, TextureCache},
@@ -71,45 +71,27 @@ impl Plugin for BloomPlugin {
                     prepare_upsampling_pipeline.in_set(RenderSet::Prepare),
                     queue_bloom_bind_groups.in_set(RenderSet::Queue),
                 ),
-            );
+            )
-
             // Add bloom to the 3d render graph
-        {
+            .add_render_graph_node::<BloomNode>(core_3d::graph::NAME, core_3d::graph::node::BLOOM)
-            let bloom_node = BloomNode::new(&mut render_app.world);
+            .add_render_graph_edges(
-            let mut graph = render_app.world.resource_mut::<RenderGraph>();
+                core_3d::graph::NAME,
-            let draw_3d_graph = graph
+                &[
-                .get_sub_graph_mut(crate::core_3d::graph::NAME)
+                    core_3d::graph::node::END_MAIN_PASS,
-                .unwrap();
-            draw_3d_graph.add_node(core_3d::graph::node::BLOOM, bloom_node);
-            // MAIN_PASS -> BLOOM -> TONEMAPPING
-            draw_3d_graph.add_node_edge(
-                crate::core_3d::graph::node::END_MAIN_PASS,
                     core_3d::graph::node::BLOOM,
-            );
+                    core_3d::graph::node::TONEMAPPING,
-            draw_3d_graph.add_node_edge(
+                ],
-                core_3d::graph::node::BLOOM,
+            )
-                crate::core_3d::graph::node::TONEMAPPING,
-            );
-        }
-
             // Add bloom to the 2d render graph
-        {
+            .add_render_graph_node::<BloomNode>(core_2d::graph::NAME, core_2d::graph::node::BLOOM)
-            let bloom_node = BloomNode::new(&mut render_app.world);
+            .add_render_graph_edges(
-            let mut graph = render_app.world.resource_mut::<RenderGraph>();
+                core_2d::graph::NAME,
-            let draw_2d_graph = graph
+                &[
-                .get_sub_graph_mut(crate::core_2d::graph::NAME)
+                    core_2d::graph::node::MAIN_PASS,
-                .unwrap();
-            draw_2d_graph.add_node(core_2d::graph::node::BLOOM, bloom_node);
-            // MAIN_PASS -> BLOOM -> TONEMAPPING
-            draw_2d_graph.add_node_edge(
-                crate::core_2d::graph::node::MAIN_PASS,
                     core_2d::graph::node::BLOOM,
+                    core_2d::graph::node::TONEMAPPING,
+                ],
             );
-            draw_2d_graph.add_node_edge(
-                core_2d::graph::node::BLOOM,
-                crate::core_2d::graph::node::TONEMAPPING,
-            );
-        }
     }
 }
 
@@ -126,8 +108,8 @@ pub struct BloomNode {
     )>,
 }
 
-impl BloomNode {
+impl FromWorld for BloomNode {
-    pub fn new(world: &mut World) -> Self {
+    fn from_world(world: &mut World) -> Self {
         Self {
             view_query: QueryState::new(world),
         }

crates/bevy_core_pipeline/src/contrast_adaptive_sharpening/mod.rs

@@ -6,7 +6,7 @@ use bevy_reflect::{Reflect, TypeUuid};
 use bevy_render::{
     extract_component::{ExtractComponent, ExtractComponentPlugin, UniformComponentPlugin},
     prelude::Camera,
-    render_graph::RenderGraph,
+    render_graph::RenderGraphApp,
     render_resource::*,
     renderer::RenderDevice,
     texture::BevyDefault,
@@ -114,49 +114,49 @@ impl Plugin for CASPlugin {
         render_app
             .init_resource::<CASPipeline>()
             .init_resource::<SpecializedRenderPipelines<CASPipeline>>()
-            .add_systems(Render, prepare_cas_pipelines.in_set(RenderSet::Prepare));
+            .add_systems(Render, prepare_cas_pipelines.in_set(RenderSet::Prepare))
-        {
+            // 3d
-            let cas_node = CASNode::new(&mut render_app.world);
+            .add_render_graph_node::<CASNode>(
-            let mut binding = render_app.world.resource_mut::<RenderGraph>();
+                core_3d::graph::NAME,
-            let graph = binding.get_sub_graph_mut(core_3d::graph::NAME).unwrap();
+                core_3d::graph::node::CONTRAST_ADAPTIVE_SHARPENING,
-
+            )
-            graph.add_node(core_3d::graph::node::CONTRAST_ADAPTIVE_SHARPENING, cas_node);
+            .add_render_graph_edge(
-
+                core_3d::graph::NAME,
-            graph.add_node_edge(
                 core_3d::graph::node::TONEMAPPING,
                 core_3d::graph::node::CONTRAST_ADAPTIVE_SHARPENING,
-            );
+            )
-            graph.add_node_edge(
+            .add_render_graph_edge(
+                core_3d::graph::NAME,
                 core_3d::graph::node::FXAA,
                 core_3d::graph::node::CONTRAST_ADAPTIVE_SHARPENING,
-            );
+            )
-            graph.add_node_edge(
+            .add_render_graph_edge(
+                core_3d::graph::NAME,
                 core_3d::graph::node::CONTRAST_ADAPTIVE_SHARPENING,
                 core_3d::graph::node::END_MAIN_PASS_POST_PROCESSING,
-            );
+            )
-        }
+            // 2d
-        {
+            .add_render_graph_node::<CASNode>(
-            let cas_node = CASNode::new(&mut render_app.world);
+                core_2d::graph::NAME,
-            let mut binding = render_app.world.resource_mut::<RenderGraph>();
+                core_2d::graph::node::CONTRAST_ADAPTIVE_SHARPENING,
-            let graph = binding.get_sub_graph_mut(core_2d::graph::NAME).unwrap();
+            )
-
+            .add_render_graph_edge(
-            graph.add_node(core_2d::graph::node::CONTRAST_ADAPTIVE_SHARPENING, cas_node);
+                core_2d::graph::NAME,
-
-            graph.add_node_edge(
                 core_2d::graph::node::TONEMAPPING,
                 core_2d::graph::node::CONTRAST_ADAPTIVE_SHARPENING,
-            );
+            )
-            graph.add_node_edge(
+            .add_render_graph_edge(
+                core_2d::graph::NAME,
                 core_2d::graph::node::FXAA,
                 core_2d::graph::node::CONTRAST_ADAPTIVE_SHARPENING,
-            );
+            )
-            graph.add_node_edge(
+            .add_render_graph_edge(
+                core_2d::graph::NAME,
                 core_2d::graph::node::CONTRAST_ADAPTIVE_SHARPENING,
                 core_2d::graph::node::END_MAIN_PASS_POST_PROCESSING,
             );
     }
 }
-}
 
 #[derive(Resource)]
 pub struct CASPipeline {

crates/bevy_core_pipeline/src/contrast_adaptive_sharpening/node.rs

@@ -28,8 +28,8 @@ pub struct CASNode {
     cached_bind_group: Mutex<Option<(BufferId, TextureViewId, BindGroup)>>,
 }
 
-impl CASNode {
+impl FromWorld for CASNode {
-    pub fn new(world: &mut World) -> Self {
+    fn from_world(world: &mut World) -> Self {
         Self {
             query: QueryState::new(world),
             cached_bind_group: Mutex::new(None),

crates/bevy_core_pipeline/src/core_2d/mod.rs

@@ -74,15 +74,14 @@ impl Plugin for Core2dPlugin {
         draw_2d_graph.add_node(graph::node::TONEMAPPING, tonemapping);
         draw_2d_graph.add_node(graph::node::END_MAIN_PASS_POST_PROCESSING, EmptyNode);
         draw_2d_graph.add_node(graph::node::UPSCALING, upscaling);
-        draw_2d_graph.add_node_edge(graph::node::MAIN_PASS, graph::node::TONEMAPPING);
+
-        draw_2d_graph.add_node_edge(
+        draw_2d_graph.add_node_edges(&[
+            graph::node::MAIN_PASS,
             graph::node::TONEMAPPING,
             graph::node::END_MAIN_PASS_POST_PROCESSING,
-        );
-        draw_2d_graph.add_node_edge(
-            graph::node::END_MAIN_PASS_POST_PROCESSING,
             graph::node::UPSCALING,
-        );
+        ]);
+
         graph.add_sub_graph(graph::NAME, draw_2d_graph);
     }
 }

crates/bevy_core_pipeline/src/core_3d/mod.rs

@@ -106,25 +106,17 @@ impl Plugin for Core3dPlugin {
         draw_3d_graph.add_node(graph::node::END_MAIN_PASS_POST_PROCESSING, EmptyNode);
         draw_3d_graph.add_node(graph::node::UPSCALING, upscaling);
 
-        draw_3d_graph.add_node_edge(graph::node::PREPASS, graph::node::START_MAIN_PASS);
+        draw_3d_graph.add_node_edges(&[
-        draw_3d_graph.add_node_edge(graph::node::START_MAIN_PASS, graph::node::MAIN_OPAQUE_PASS);
+            graph::node::PREPASS,
-        draw_3d_graph.add_node_edge(
+            graph::node::START_MAIN_PASS,
             graph::node::MAIN_OPAQUE_PASS,
             graph::node::MAIN_TRANSPARENT_PASS,
-        );
-        draw_3d_graph.add_node_edge(
-            graph::node::MAIN_TRANSPARENT_PASS,
             graph::node::END_MAIN_PASS,
-        );
-        draw_3d_graph.add_node_edge(graph::node::END_MAIN_PASS, graph::node::TONEMAPPING);
-        draw_3d_graph.add_node_edge(
             graph::node::TONEMAPPING,
             graph::node::END_MAIN_PASS_POST_PROCESSING,
-        );
-        draw_3d_graph.add_node_edge(
-            graph::node::END_MAIN_PASS_POST_PROCESSING,
             graph::node::UPSCALING,
-        );
+        ]);
+
         graph.add_sub_graph(graph::NAME, draw_3d_graph);
     }
 }

crates/bevy_core_pipeline/src/fxaa/mod.rs

@@ -9,7 +9,7 @@ use bevy_reflect::{
 use bevy_render::{
     extract_component::{ExtractComponent, ExtractComponentPlugin},
     prelude::Camera,
-    render_graph::RenderGraph,
+    render_graph::RenderGraphApp,
     render_resource::*,
     renderer::RenderDevice,
     texture::BevyDefault,
@@ -90,42 +90,27 @@ impl Plugin for FxaaPlugin {
         render_app
             .init_resource::<FxaaPipeline>()
             .init_resource::<SpecializedRenderPipelines<FxaaPipeline>>()
-            .add_systems(Render, prepare_fxaa_pipelines.in_set(RenderSet::Prepare));
+            .add_systems(Render, prepare_fxaa_pipelines.in_set(RenderSet::Prepare))
-
+            .add_render_graph_node::<FxaaNode>(core_3d::graph::NAME, core_3d::graph::node::FXAA)
-        {
+            .add_render_graph_edges(
-            let fxaa_node = FxaaNode::new(&mut render_app.world);
+                core_3d::graph::NAME,
-            let mut binding = render_app.world.resource_mut::<RenderGraph>();
+                &[
-            let graph = binding.get_sub_graph_mut(core_3d::graph::NAME).unwrap();
-
-            graph.add_node(core_3d::graph::node::FXAA, fxaa_node);
-
-            graph.add_node_edge(
                     core_3d::graph::node::TONEMAPPING,
                     core_3d::graph::node::FXAA,
-            );
-            graph.add_node_edge(
-                core_3d::graph::node::FXAA,
                     core_3d::graph::node::END_MAIN_PASS_POST_PROCESSING,
-            );
+                ],
-        }
+            )
-        {
+            .add_render_graph_node::<FxaaNode>(core_2d::graph::NAME, core_2d::graph::node::FXAA)
-            let fxaa_node = FxaaNode::new(&mut render_app.world);
+            .add_render_graph_edges(
-            let mut binding = render_app.world.resource_mut::<RenderGraph>();
+                core_2d::graph::NAME,
-            let graph = binding.get_sub_graph_mut(core_2d::graph::NAME).unwrap();
+                &[
-
-            graph.add_node(core_2d::graph::node::FXAA, fxaa_node);
-
-            graph.add_node_edge(
                     core_2d::graph::node::TONEMAPPING,
                     core_2d::graph::node::FXAA,
-            );
-            graph.add_node_edge(
-                core_2d::graph::node::FXAA,
                     core_2d::graph::node::END_MAIN_PASS_POST_PROCESSING,
+                ],
             );
     }
 }
-}
 
 #[derive(Resource, Deref)]
 pub struct FxaaPipeline {

crates/bevy_core_pipeline/src/fxaa/node.rs

@@ -27,8 +27,8 @@ pub struct FxaaNode {
     cached_texture_bind_group: Mutex<Option<(TextureViewId, BindGroup)>>,
 }
 
-impl FxaaNode {
+impl FromWorld for FxaaNode {
-    pub fn new(world: &mut World) -> Self {
+    fn from_world(world: &mut World) -> Self {
         Self {
             query: QueryState::new(world),
             cached_texture_bind_group: Mutex::new(None),

crates/bevy_core_pipeline/src/taa/mod.rs

@@ -1,4 +1,5 @@
 use crate::{
+    core_3d,
     fullscreen_vertex_shader::fullscreen_shader_vertex_state,
     prelude::Camera3d,
     prepass::{DepthPrepass, MotionVectorPrepass, ViewPrepassTextures},
@@ -18,7 +19,7 @@ use bevy_reflect::{Reflect, TypeUuid};
 use bevy_render::{
     camera::{ExtractedCamera, TemporalJitter},
     prelude::{Camera, Projection},
-    render_graph::{Node, NodeRunError, RenderGraph, RenderGraphContext},
+    render_graph::{Node, NodeRunError, RenderGraphApp, RenderGraphContext},
     render_resource::{
         BindGroupDescriptor, BindGroupEntry, BindGroupLayout, BindGroupLayoutDescriptor,
         BindGroupLayoutEntry, BindingResource, BindingType, CachedRenderPipelineId,
@@ -71,23 +72,16 @@ impl Plugin for TemporalAntiAliasPlugin {
                     prepare_taa_history_textures.in_set(RenderSet::Prepare),
                     prepare_taa_pipelines.in_set(RenderSet::Prepare),
                 ),
-            );
+            )
-
+            .add_render_graph_node::<TAANode>(core_3d::graph::NAME, draw_3d_graph::node::TAA)
-        let taa_node = TAANode::new(&mut render_app.world);
+            .add_render_graph_edges(
-        let mut graph = render_app.world.resource_mut::<RenderGraph>();
+                core_3d::graph::NAME,
-        let draw_3d_graph = graph
+                &[
-            .get_sub_graph_mut(crate::core_3d::graph::NAME)
+                    core_3d::graph::node::END_MAIN_PASS,
-            .unwrap();
-        draw_3d_graph.add_node(draw_3d_graph::node::TAA, taa_node);
-        // MAIN_PASS -> TAA -> BLOOM -> TONEMAPPING
-        draw_3d_graph.add_node_edge(
-            crate::core_3d::graph::node::END_MAIN_PASS,
                     draw_3d_graph::node::TAA,
-        );
+                    core_3d::graph::node::BLOOM,
-        draw_3d_graph.add_node_edge(draw_3d_graph::node::TAA, crate::core_3d::graph::node::BLOOM);
+                    core_3d::graph::node::TONEMAPPING,
-        draw_3d_graph.add_node_edge(
+                ],
-            draw_3d_graph::node::TAA,
-            crate::core_3d::graph::node::TONEMAPPING,
             );
     }
 }
@@ -168,8 +162,8 @@ struct TAANode {
     )>,
 }
 
-impl TAANode {
+impl FromWorld for TAANode {
-    fn new(world: &mut World) -> Self {
+    fn from_world(world: &mut World) -> Self {
         Self {
             view_query: QueryState::new(world),
         }

crates/bevy_render/src/render_graph/app.rs

@@ -0,0 +1,73 @@
+use bevy_app::App;
+use bevy_ecs::world::FromWorld;
+
+use super::{Node, RenderGraph};
+
+/// Adds common [`RenderGraph`] operations to [`App`].
+pub trait RenderGraphApp {
+    /// Add a [`Node`] to the [`RenderGraph`]:
+    /// * Create the [`Node`] using the [`FromWorld`] implementation
+    /// * Add it to the graph
+    fn add_render_graph_node<T: Node + FromWorld>(
+        &mut self,
+        sub_graph_name: &'static str,
+        node_name: &'static str,
+    ) -> &mut Self;
+    /// Automatically add the required node edges based on the given ordering
+    fn add_render_graph_edges(
+        &mut self,
+        sub_graph_name: &'static str,
+        edges: &[&'static str],
+    ) -> &mut Self;
+    /// Add node edge to the specified graph
+    fn add_render_graph_edge(
+        &mut self,
+        sub_graph_name: &'static str,
+        output_edge: &'static str,
+        input_edge: &'static str,
+    ) -> &mut Self;
+}
+
+impl RenderGraphApp for App {
+    fn add_render_graph_node<T: Node + FromWorld>(
+        &mut self,
+        sub_graph_name: &'static str,
+        node_name: &'static str,
+    ) -> &mut Self {
+        let node = T::from_world(&mut self.world);
+        let mut render_graph = self.world.get_resource_mut::<RenderGraph>().expect(
+            "RenderGraph not found. Make sure you are using add_render_graph_node on the RenderApp",
+        );
+
+        let graph = render_graph.sub_graph_mut(sub_graph_name);
+        graph.add_node(node_name, node);
+        self
+    }
+
+    fn add_render_graph_edges(
+        &mut self,
+        sub_graph_name: &'static str,
+        edges: &[&'static str],
+    ) -> &mut Self {
+        let mut render_graph = self.world.get_resource_mut::<RenderGraph>().expect(
+            "RenderGraph not found. Make sure you are using add_render_graph_node on the RenderApp",
+        );
+        let graph = render_graph.sub_graph_mut(sub_graph_name);
+        graph.add_node_edges(edges);
+        self
+    }
+
+    fn add_render_graph_edge(
+        &mut self,
+        sub_graph_name: &'static str,
+        output_edge: &'static str,
+        input_edge: &'static str,
+    ) -> &mut Self {
+        let mut render_graph = self.world.get_resource_mut::<RenderGraph>().expect(
+            "RenderGraph not found. Make sure you are using add_render_graph_node on the RenderApp",
+        );
+        let graph = render_graph.sub_graph_mut(sub_graph_name);
+        graph.add_node_edge(output_edge, input_edge);
+        self
+    }
+}

crates/bevy_render/src/render_graph/graph.rs

@@ -119,6 +119,24 @@ impl RenderGraph {
         id
     }
 
+    /// Add `node_edge`s based on the order of the given `edges` array.
+    ///
+    /// Defining an edge that already exists is not considered an error with this api.
+    /// It simply won't create a new edge.
+    pub fn add_node_edges(&mut self, edges: &[&'static str]) {
+        for window in edges.windows(2) {
+            let [a, b] = window else { break; };
+            if let Err(err) = self.try_add_node_edge(*a, *b) {
+                match err {
+                    // Already existing edges are very easy to produce with this api
+                    // and shouldn't cause a panic
+                    RenderGraphError::EdgeAlreadyExists(_) => {}
+                    _ => panic!("{err:?}"),
+                }
+            }
+        }
+    }
+
     /// Removes the `node` with the `name` from the graph.
     /// If the name is does not exist, nothing happens.
     pub fn remove_node(
@@ -583,6 +601,36 @@ impl RenderGraph {
     pub fn get_sub_graph_mut(&mut self, name: impl AsRef<str>) -> Option<&mut RenderGraph> {
         self.sub_graphs.get_mut(name.as_ref())
     }
+
+    /// Retrieves the sub graph corresponding to the `name`.
+    ///
+    /// # Panics
+    ///
+    /// Panics if any invalid node name is given.
+    ///
+    /// # See also
+    ///
+    /// - [`get_sub_graph`](Self::get_sub_graph) for a fallible version.
+    pub fn sub_graph(&self, name: impl AsRef<str>) -> &RenderGraph {
+        self.sub_graphs
+            .get(name.as_ref())
+            .unwrap_or_else(|| panic!("Node {} not found in sub_graph", name.as_ref()))
+    }
+
+    /// Retrieves the sub graph corresponding to the `name` mutably.
+    ///
+    /// # Panics
+    ///
+    /// Panics if any invalid node name is given.
+    ///
+    /// # See also
+    ///
+    /// - [`get_sub_graph_mut`](Self::get_sub_graph_mut) for a fallible version.
+    pub fn sub_graph_mut(&mut self, name: impl AsRef<str>) -> &mut RenderGraph {
+        self.sub_graphs
+            .get_mut(name.as_ref())
+            .unwrap_or_else(|| panic!("Node {} not found in sub_graph", name.as_ref()))
+    }
 }
 
 impl Debug for RenderGraph {
@@ -635,7 +683,7 @@ mod tests {
         },
         renderer::RenderContext,
     };
-    use bevy_ecs::world::World;
+    use bevy_ecs::world::{FromWorld, World};
     use bevy_utils::HashSet;
 
     #[derive(Debug)]
@@ -676,18 +724,6 @@ mod tests {
         }
     }
 
-    #[test]
-    fn test_graph_edges() {
-        let mut graph = RenderGraph::default();
-        let a_id = graph.add_node("A", TestNode::new(0, 1));
-        let b_id = graph.add_node("B", TestNode::new(0, 1));
-        let c_id = graph.add_node("C", TestNode::new(1, 1));
-        let d_id = graph.add_node("D", TestNode::new(1, 0));
-
-        graph.add_slot_edge("A", "out_0", "C", "in_0");
-        graph.add_node_edge("B", "C");
-        graph.add_slot_edge("C", 0, "D", 0);
-
     fn input_nodes(name: &'static str, graph: &RenderGraph) -> HashSet<NodeId> {
         graph
             .iter_node_inputs(name)
@@ -704,6 +740,18 @@ mod tests {
             .collect::<HashSet<NodeId>>()
     }
 
+    #[test]
+    fn test_graph_edges() {
+        let mut graph = RenderGraph::default();
+        let a_id = graph.add_node("A", TestNode::new(0, 1));
+        let b_id = graph.add_node("B", TestNode::new(0, 1));
+        let c_id = graph.add_node("C", TestNode::new(1, 1));
+        let d_id = graph.add_node("D", TestNode::new(1, 0));
+
+        graph.add_slot_edge("A", "out_0", "C", "in_0");
+        graph.add_node_edge("B", "C");
+        graph.add_slot_edge("C", 0, "D", 0);
+
         assert!(input_nodes("A", &graph).is_empty(), "A has no inputs");
         assert!(
             output_nodes("A", &graph) == HashSet::from_iter(vec![c_id]),
@@ -803,4 +851,48 @@ mod tests {
             "Adding to a duplicate edge should return an error"
         );
     }
+
+    #[test]
+    fn test_add_node_edges() {
+        struct SimpleNode;
+        impl Node for SimpleNode {
+            fn run(
+                &self,
+                _graph: &mut RenderGraphContext,
+                _render_context: &mut RenderContext,
+                _world: &World,
+            ) -> Result<(), NodeRunError> {
+                Ok(())
+            }
+        }
+        impl FromWorld for SimpleNode {
+            fn from_world(_world: &mut World) -> Self {
+                Self
+            }
+        }
+
+        let mut graph = RenderGraph::default();
+        let a_id = graph.add_node("A", SimpleNode);
+        let b_id = graph.add_node("B", SimpleNode);
+        let c_id = graph.add_node("C", SimpleNode);
+
+        graph.add_node_edges(&["A", "B", "C"]);
+
+        assert!(
+            output_nodes("A", &graph) == HashSet::from_iter(vec![b_id]),
+            "A -> B"
+        );
+        assert!(
+            input_nodes("B", &graph) == HashSet::from_iter(vec![a_id]),
+            "A -> B"
+        );
+        assert!(
+            output_nodes("B", &graph) == HashSet::from_iter(vec![c_id]),
+            "B -> C"
+        );
+        assert!(
+            input_nodes("C", &graph) == HashSet::from_iter(vec![b_id]),
+            "B -> C"
+        );
+    }
 }

crates/bevy_render/src/render_graph/mod.rs

@@ -1,9 +1,11 @@
+mod app;
 mod context;
 mod edge;
 mod graph;
 mod node;
 mod node_slot;
 
+pub use app::*;
 pub use context::*;
 pub use edge::*;
 pub use graph::*;

examples/shader/post_process_pass.rs

@@ -15,7 +15,7 @@ use bevy::{
         extract_component::{
             ComponentUniforms, ExtractComponent, ExtractComponentPlugin, UniformComponentPlugin,
         },
-        render_graph::{Node, NodeRunError, RenderGraph, RenderGraphContext},
+        render_graph::{Node, NodeRunError, RenderGraphApp, RenderGraphContext},
         render_resource::{
             BindGroupDescriptor, BindGroupEntry, BindGroupLayout, BindGroupLayoutDescriptor,
             BindGroupLayoutEntry, BindingResource, BindingType, CachedRenderPipelineId,
@@ -53,7 +53,8 @@ impl Plugin for PostProcessPlugin {
             // be extracted to the render world every frame.
             // This makes it possible to control the effect from the main world.
             // This plugin will take care of extracting it automatically.
-            // It's important to derive [`ExtractComponent`] on [`PostProcessingSettings`] for this plugin to work correctly.
+            // It's important to derive [`ExtractComponent`] on [`PostProcessingSettings`]
+            // for this plugin to work correctly.
             .add_plugin(ExtractComponentPlugin::<PostProcessSettings>::default())
             // The settings will also be the data used in the shader.
             // This plugin will prepare the component for the GPU by creating a uniform buffer
@@ -65,37 +66,34 @@ impl Plugin for PostProcessPlugin {
             return;
         };
 
+        render_app
             // Initialize the pipeline
-        render_app.init_resource::<PostProcessPipeline>();
+            .init_resource::<PostProcessPipeline>()
-
             // Bevy's renderer uses a render graph which is a collection of nodes in a directed acyclic graph.
             // It currently runs on each view/camera and executes each node in the specified order.
-        // It will make sure that any node that needs a dependency from another node only runs when that dependency is done.
+            // It will make sure that any node that needs a dependency from another node
+            // only runs when that dependency is done.
             //
             // Each node can execute arbitrary work, but it generally runs at least one render pass.
             // A node only has access to the render world, so if you need data from the main world
             // you need to extract it manually or with the plugin like above.
-
+            // Add a [`Node`] to the [`RenderGraph`]
-        // Create the node with the render world
+            // The Node needs to impl FromWorld
-        let node = PostProcessNode::new(&mut render_app.world);
+            .add_render_graph_node::<PostProcessNode>(
-
+                // Specifiy the name of the graph, in this case we want the graph for 3d
-        // Get the render graph for the entire app
+                core_3d::graph::NAME,
-        let mut graph = render_app.world.resource_mut::<RenderGraph>();
+                // It also needs the name of the node
-
+                PostProcessNode::NAME,
-        // Get the render graph for 3d cameras/views
+            )
-        let core_3d_graph = graph.get_sub_graph_mut(core_3d::graph::NAME).unwrap();
+            .add_render_graph_edges(
-
+                core_3d::graph::NAME,
-        // Register the post process node in the 3d render graph
+                // Specify the node ordering.
-        core_3d_graph.add_node(PostProcessNode::NAME, node);
+                // This will automatically create all required node edges to enforce the given ordering.
-
+                &[
-        // We now need to add an edge between our node and the nodes from bevy
+                    core_3d::graph::node::TONEMAPPING,
-        // to make sure our node is ordered correctly relative to other nodes.
-        //
-        // Here we want our effect to run after tonemapping and before the end of the main pass post processing
-        core_3d_graph.add_node_edge(core_3d::graph::node::TONEMAPPING, PostProcessNode::NAME);
-        core_3d_graph.add_node_edge(
                     PostProcessNode::NAME,
                     core_3d::graph::node::END_MAIN_PASS_POST_PROCESSING,
+                ],
             );
     }
 }
@@ -109,8 +107,10 @@ struct PostProcessNode {
 
 impl PostProcessNode {
     pub const NAME: &str = "post_process";
+}
 
-    fn new(world: &mut World) -> Self {
+impl FromWorld for PostProcessNode {
+    fn from_world(world: &mut World) -> Self {
         Self {
             query: QueryState::new(world),
         }