Switch bins from parallel key/value arrays to IndexMaps. (#17819)

Conceptually, bins are ordered hash maps. We currently implement these
as a list of keys with an associated hash map. But we already have a
data type that implements ordered hash maps directly: `IndexMap`. This
patch switches Bevy to use `IndexMap`s for bins. Because we're memory
bound, this doesn't affect performance much, but it is cleaner.

Author: pcwalton

crates/bevy_core_pipeline/src/deferred/node.rs

@@ -147,9 +147,9 @@ impl ViewNode for DeferredGBufferPrepassNode {
             }
 
             // Opaque draws
-            if !opaque_deferred_phase.multidrawable_mesh_keys.is_empty()
-                || !opaque_deferred_phase.batchable_mesh_keys.is_empty()
-                || !opaque_deferred_phase.unbatchable_mesh_keys.is_empty()
+            if !opaque_deferred_phase.multidrawable_meshes.is_empty()
+                || !opaque_deferred_phase.batchable_meshes.is_empty()
+                || !opaque_deferred_phase.unbatchable_meshes.is_empty()
             {
                 #[cfg(feature = "trace")]
                 let _opaque_prepass_span = info_span!("opaque_deferred_prepass").entered();

crates/bevy_render/src/batching/gpu_preprocessing.rs

@@ -1374,11 +1374,11 @@ pub fn batch_and_prepare_binned_render_phase<BPI, GFBD>(
 
         // Prepare multidrawables.
 
-        for batch_set_key in &phase.multidrawable_mesh_keys {
+        for (batch_set_key, bins) in &phase.multidrawable_meshes {
             let mut batch_set = None;
             let indirect_parameters_base =
                 indirect_parameters_buffers.batch_count(batch_set_key.indexed()) as u32;
-            for (bin_key, bin) in &phase.multidrawable_mesh_values[batch_set_key] {
+            for (bin_key, bin) in bins {
                 let first_output_index = data_buffer.len() as u32;
                 let mut batch: Option<BinnedRenderPhaseBatch> = None;
 
@@ -1472,11 +1472,11 @@ pub fn batch_and_prepare_binned_render_phase<BPI, GFBD>(
 
         // Prepare batchables.
 
-        for key in &phase.batchable_mesh_keys {
+        for (key, bin) in &phase.batchable_meshes {
             let first_output_index = data_buffer.len() as u32;
 
             let mut batch: Option<BinnedRenderPhaseBatch> = None;
-            for (&main_entity, &input_index) in phase.batchable_mesh_values[key].entities() {
+            for (&main_entity, &input_index) in bin.entities() {
                 let output_index = data_buffer.add() as u32;
 
                 match batch {
@@ -1589,9 +1589,7 @@ pub fn batch_and_prepare_binned_render_phase<BPI, GFBD>(
         }
 
         // Prepare unbatchables.
-        for key in &phase.unbatchable_mesh_keys {
-            let unbatchables = phase.unbatchable_mesh_values.get_mut(key).unwrap();
-
+        for (key, unbatchables) in &mut phase.unbatchable_meshes {
             // Allocate the indirect parameters if necessary.
             let mut indirect_parameters_offset = if no_indirect_drawing {
                 None

crates/bevy_render/src/batching/mod.rs

@@ -190,23 +190,9 @@ where
     BPI: BinnedPhaseItem,
 {
     for phase in phases.values_mut() {
-        phase.multidrawable_mesh_keys.clear();
-        phase
-            .multidrawable_mesh_keys
-            .extend(phase.multidrawable_mesh_values.keys().cloned());
-        phase.multidrawable_mesh_keys.sort_unstable();
-
-        phase.batchable_mesh_keys.clear();
-        phase
-            .batchable_mesh_keys
-            .extend(phase.batchable_mesh_values.keys().cloned());
-        phase.batchable_mesh_keys.sort_unstable();
-
-        phase.unbatchable_mesh_keys.clear();
-        phase
-            .unbatchable_mesh_keys
-            .extend(phase.unbatchable_mesh_values.keys().cloned());
-        phase.unbatchable_mesh_keys.sort_unstable();
+        phase.multidrawable_meshes.sort_unstable_keys();
+        phase.batchable_meshes.sort_unstable_keys();
+        phase.unbatchable_meshes.sort_unstable_keys();
     }
 }
 

crates/bevy_render/src/batching/no_gpu_preprocessing.rs

@@ -108,9 +108,9 @@ pub fn batch_and_prepare_binned_render_phase<BPI, GFBD>(
     for phase in phases.values_mut() {
         // Prepare batchables.
 
-        for key in &phase.batchable_mesh_keys {
+        for bin in phase.batchable_meshes.values_mut() {
             let mut batch_set: SmallVec<[BinnedRenderPhaseBatch; 1]> = smallvec![];
-            for main_entity in phase.batchable_mesh_values[key].entities().keys() {
+            for main_entity in bin.entities().keys() {
                 let Some(buffer_data) =
                     GFBD::get_binned_batch_data(&system_param_item, *main_entity)
                 else {
@@ -156,8 +156,7 @@ pub fn batch_and_prepare_binned_render_phase<BPI, GFBD>(
         }
 
         // Prepare unbatchables.
-        for key in &phase.unbatchable_mesh_keys {
-            let unbatchables = phase.unbatchable_mesh_values.get_mut(key).unwrap();
+        for unbatchables in phase.unbatchable_meshes.values_mut() {
             for main_entity in unbatchables.entities.keys() {
                 let Some(buffer_data) =
                     GFBD::get_binned_batch_data(&system_param_item, *main_entity)