bevy_render/renderer/
graph_runner.rs

1use bevy_ecs::{prelude::Entity, world::World};
2use bevy_platform::collections::HashMap;
3#[cfg(feature = "trace")]
4use tracing::info_span;
5
6use alloc::{borrow::Cow, collections::VecDeque};
7use smallvec::{smallvec, SmallVec};
8use thiserror::Error;
9
10use crate::{
11    diagnostic::internal::{DiagnosticsRecorder, RenderDiagnosticsMutex},
12    render_graph::{
13        Edge, InternedRenderLabel, InternedRenderSubGraph, NodeRunError, NodeState, RenderGraph,
14        RenderGraphContext, SlotLabel, SlotType, SlotValue,
15    },
16    renderer::{RenderContext, RenderDevice},
17};
18
19/// The [`RenderGraphRunner`] is responsible for executing a [`RenderGraph`].
20///
21/// It will run all nodes in the graph sequentially in the correct order (defined by the edges).
22/// Each [`Node`](crate::render_graph::Node) can run any arbitrary code, but will generally
23/// either send directly a [`CommandBuffer`] or a task that will asynchronously generate a [`CommandBuffer`]
24///
25/// After running the graph, the [`RenderGraphRunner`] will execute in parallel all the tasks to get
26/// an ordered list of [`CommandBuffer`]s to execute. These [`CommandBuffer`] will be submitted to the GPU
27/// sequentially in the order that the tasks were submitted. (which is the order of the [`RenderGraph`])
28///
29/// [`CommandBuffer`]: wgpu::CommandBuffer
30pub(crate) struct RenderGraphRunner;
31
32#[derive(Error, Debug)]
33pub enum RenderGraphRunnerError {
34    #[error(transparent)]
35    NodeRunError(#[from] NodeRunError),
36    #[error("node output slot not set (index {slot_index}, name {slot_name})")]
37    EmptyNodeOutputSlot {
38        type_name: &'static str,
39        slot_index: usize,
40        slot_name: Cow<'static, str>,
41    },
42    #[error("graph '{sub_graph:?}' could not be run because slot '{slot_name}' at index {slot_index} has no value")]
43    MissingInput {
44        slot_index: usize,
45        slot_name: Cow<'static, str>,
46        sub_graph: Option<InternedRenderSubGraph>,
47    },
48    #[error("attempted to use the wrong type for input slot")]
49    MismatchedInputSlotType {
50        slot_index: usize,
51        label: SlotLabel,
52        expected: SlotType,
53        actual: SlotType,
54    },
55    #[error(
56        "node (name: '{node_name:?}') has {slot_count} input slots, but was provided {value_count} values"
57    )]
58    MismatchedInputCount {
59        node_name: InternedRenderLabel,
60        slot_count: usize,
61        value_count: usize,
62    },
63}
64
65impl RenderGraphRunner {
66    pub fn run(
67        graph: &RenderGraph,
68        render_device: RenderDevice,
69        mut diagnostics_recorder: Option<DiagnosticsRecorder>,
70        queue: &wgpu::Queue,
71        world: &World,
72        finalizer: impl FnOnce(&mut wgpu::CommandEncoder),
73    ) -> Result<Option<DiagnosticsRecorder>, RenderGraphRunnerError> {
74        if let Some(recorder) = &mut diagnostics_recorder {
75            recorder.begin_frame();
76        }
77
78        let mut render_context = RenderContext::new(render_device, diagnostics_recorder);
79        Self::run_graph(graph, None, &mut render_context, world, &[], None)?;
80        finalizer(render_context.command_encoder());
81
82        let (render_device, mut diagnostics_recorder) = {
83            let (commands, render_device, diagnostics_recorder) = render_context.finish();
84
85            #[cfg(feature = "trace")]
86            let _span = info_span!("submit_graph_commands").entered();
87            queue.submit(commands);
88
89            (render_device, diagnostics_recorder)
90        };
91
92        if let Some(recorder) = &mut diagnostics_recorder {
93            let render_diagnostics_mutex = world.resource::<RenderDiagnosticsMutex>().0.clone();
94            recorder.finish_frame(&render_device, move |diagnostics| {
95                *render_diagnostics_mutex.lock().expect("lock poisoned") = Some(diagnostics);
96            });
97        }
98
99        Ok(diagnostics_recorder)
100    }
101
102    /// Runs the [`RenderGraph`] and all its sub-graphs sequentially, making sure that all nodes are
103    /// run in the correct order. (a node only runs when all its dependencies have finished running)
104    fn run_graph<'w>(
105        graph: &RenderGraph,
106        sub_graph: Option<InternedRenderSubGraph>,
107        render_context: &mut RenderContext<'w>,
108        world: &'w World,
109        inputs: &[SlotValue],
110        view_entity: Option<Entity>,
111    ) -> Result<(), RenderGraphRunnerError> {
112        let mut node_outputs: HashMap<InternedRenderLabel, SmallVec<[SlotValue; 4]>> =
113            HashMap::default();
114        #[cfg(feature = "trace")]
115        let span = if let Some(label) = &sub_graph {
116            info_span!("run_graph", name = format!("{label:?}"))
117        } else {
118            info_span!("run_graph", name = "main_graph")
119        };
120        #[cfg(feature = "trace")]
121        let _guard = span.enter();
122
123        // Queue up nodes without inputs, which can be run immediately
124        let mut node_queue: VecDeque<&NodeState> = graph
125            .iter_nodes()
126            .filter(|node| node.input_slots.is_empty())
127            .collect();
128
129        // pass inputs into the graph
130        if let Some(input_node) = graph.get_input_node() {
131            let mut input_values: SmallVec<[SlotValue; 4]> = SmallVec::new();
132            for (i, input_slot) in input_node.input_slots.iter().enumerate() {
133                if let Some(input_value) = inputs.get(i) {
134                    if input_slot.slot_type != input_value.slot_type() {
135                        return Err(RenderGraphRunnerError::MismatchedInputSlotType {
136                            slot_index: i,
137                            actual: input_value.slot_type(),
138                            expected: input_slot.slot_type,
139                            label: input_slot.name.clone().into(),
140                        });
141                    }
142                    input_values.push(input_value.clone());
143                } else {
144                    return Err(RenderGraphRunnerError::MissingInput {
145                        slot_index: i,
146                        slot_name: input_slot.name.clone(),
147                        sub_graph,
148                    });
149                }
150            }
151
152            node_outputs.insert(input_node.label, input_values);
153
154            for (_, node_state) in graph
155                .iter_node_outputs(input_node.label)
156                .expect("node exists")
157            {
158                node_queue.push_front(node_state);
159            }
160        }
161
162        'handle_node: while let Some(node_state) = node_queue.pop_back() {
163            // skip nodes that are already processed
164            if node_outputs.contains_key(&node_state.label) {
165                continue;
166            }
167
168            let mut slot_indices_and_inputs: SmallVec<[(usize, SlotValue); 4]> = SmallVec::new();
169            // check if all dependencies have finished running
170            for (edge, input_node) in graph
171                .iter_node_inputs(node_state.label)
172                .expect("node is in graph")
173            {
174                match edge {
175                    Edge::SlotEdge {
176                        output_index,
177                        input_index,
178                        ..
179                    } => {
180                        if let Some(outputs) = node_outputs.get(&input_node.label) {
181                            slot_indices_and_inputs
182                                .push((*input_index, outputs[*output_index].clone()));
183                        } else {
184                            node_queue.push_front(node_state);
185                            continue 'handle_node;
186                        }
187                    }
188                    Edge::NodeEdge { .. } => {
189                        if !node_outputs.contains_key(&input_node.label) {
190                            node_queue.push_front(node_state);
191                            continue 'handle_node;
192                        }
193                    }
194                }
195            }
196
197            // construct final sorted input list
198            slot_indices_and_inputs.sort_by_key(|(index, _)| *index);
199            let inputs: SmallVec<[SlotValue; 4]> = slot_indices_and_inputs
200                .into_iter()
201                .map(|(_, value)| value)
202                .collect();
203
204            if inputs.len() != node_state.input_slots.len() {
205                return Err(RenderGraphRunnerError::MismatchedInputCount {
206                    node_name: node_state.label,
207                    slot_count: node_state.input_slots.len(),
208                    value_count: inputs.len(),
209                });
210            }
211
212            let mut outputs: SmallVec<[Option<SlotValue>; 4]> =
213                smallvec![None; node_state.output_slots.len()];
214            {
215                let mut context = RenderGraphContext::new(graph, node_state, &inputs, &mut outputs);
216                if let Some(view_entity) = view_entity {
217                    context.set_view_entity(view_entity);
218                }
219
220                {
221                    #[cfg(feature = "trace")]
222                    let _span = info_span!("node", name = node_state.type_name).entered();
223
224                    node_state.node.run(&mut context, render_context, world)?;
225                }
226
227                for run_sub_graph in context.finish() {
228                    let sub_graph = graph
229                        .get_sub_graph(run_sub_graph.sub_graph)
230                        .expect("sub graph exists because it was validated when queued.");
231                    Self::run_graph(
232                        sub_graph,
233                        Some(run_sub_graph.sub_graph),
234                        render_context,
235                        world,
236                        &run_sub_graph.inputs,
237                        run_sub_graph.view_entity,
238                    )?;
239                }
240            }
241
242            let mut values: SmallVec<[SlotValue; 4]> = SmallVec::new();
243            for (i, output) in outputs.into_iter().enumerate() {
244                if let Some(value) = output {
245                    values.push(value);
246                } else {
247                    let empty_slot = node_state.output_slots.get_slot(i).unwrap();
248                    return Err(RenderGraphRunnerError::EmptyNodeOutputSlot {
249                        type_name: node_state.type_name,
250                        slot_index: i,
251                        slot_name: empty_slot.name.clone(),
252                    });
253                }
254            }
255            node_outputs.insert(node_state.label, values);
256
257            for (_, node_state) in graph
258                .iter_node_outputs(node_state.label)
259                .expect("node exists")
260            {
261                node_queue.push_front(node_state);
262            }
263        }
264
265        Ok(())
266    }
267}
bevy_render/renderer/graph_runner.rs

bevy_render/renderer/
graph_runner.rs
