Disable broken effect batching

Batching of compatible effects (and in particular, multiple instances of
the same effect) is currently broken due to the inability for a particle
to tell which effect it's associated with, and therefore which
`GpuSpawnerParams` struct it should index.

To prevent batching to trigger, set the minimum buffer capacity to 1
particle, which effectively means each effect will get a dedicated GPU
buffer that just fits it, preventing another effect from using the same
buffer, and effectively disabling batching.o

Bug: #73

Cargo.toml

@@ -85,6 +85,10 @@ required-features = [ "bevy/bevy_winit", "bevy/bevy_sprite", "2d" ]
 name = "lifetime"
 required-features = [ "bevy/bevy_winit", "bevy/bevy_pbr", "3d" ]
 
+[[example]]
+name = "instancing"
+required-features = [ "bevy/bevy_winit", "bevy/bevy_pbr", "3d" ]
+
 [workspace]
 resolver = "2"
 members = ["."]

examples/instancing.rs

@@ -0,0 +1,91 @@
+use bevy::{prelude::*, render::mesh::shape::Cube};
+use bevy_inspector_egui::WorldInspectorPlugin;
+
+use bevy_hanabi::prelude::*;
+
+fn main() {
+    App::default()
+        .insert_resource(bevy::log::LogSettings {
+            level: bevy::log::Level::WARN,
+            filter: "bevy_hanabi=trace,instancing=trace".to_string(),
+        })
+        .add_plugins(DefaultPlugins)
+        .add_system(bevy::window::close_on_esc)
+        .add_plugin(HanabiPlugin)
+        .add_plugin(WorldInspectorPlugin::new())
+        .add_startup_system(setup)
+        .run();
+}
+
+fn setup(
+    mut commands: Commands,
+    mut effects: ResMut<Assets<EffectAsset>>,
+    mut meshes: ResMut<Assets<Mesh>>,
+    mut materials: ResMut<Assets<StandardMaterial>>,
+) {
+    let mut camera = Camera3dBundle::default();
+    camera.transform.translation = Vec3::new(0.0, 0.0, 180.0);
+    commands.spawn_bundle(camera);
+
+    commands.spawn_bundle(DirectionalLightBundle {
+        directional_light: DirectionalLight {
+            color: Color::WHITE,
+            // Crank the illuminance way (too) high to make the reference cube clearly visible
+            illuminance: 100000.,
+            shadows_enabled: false,
+            ..Default::default()
+        },
+        ..Default::default()
+    });
+
+    let cube = meshes.add(Mesh::from(Cube { size: 1.0 }));
+    let mat = materials.add(Color::PURPLE.into());
+
+    let mut gradient = Gradient::new();
+    gradient.add_key(0.0, Vec4::new(0.0, 0.0, 1.0, 1.0));
+    gradient.add_key(1.0, Vec4::splat(0.0));
+
+    let effect = effects.add(
+        EffectAsset {
+            name: "effect".to_string(),
+            capacity: 512,
+            spawner: Spawner::rate(50.0.into()),
+            ..Default::default()
+        }
+        .init(PositionSphereModifier {
+            center: Vec3::ZERO,
+            radius: 1.,
+            dimension: ShapeDimension::Volume,
+            speed: 2.0.into(),
+        })
+        .init(ParticleLifetimeModifier { lifetime: 12.0 })
+        .render(ColorOverLifetimeModifier { gradient }),
+    );
+
+    for j in -4..=4 {
+        for i in -5..=5 {
+            commands
+                .spawn()
+                .insert(Name::new(format!("({},{})", i, j)))
+                .insert_bundle(ParticleEffectBundle {
+                    effect: ParticleEffect::new(effect.clone()),
+                    transform: Transform::from_translation(Vec3::new(
+                        i as f32 * 10.,
+                        j as f32 * 10.,
+                        0.,
+                    )),
+                    ..Default::default()
+                })
+                .with_children(|p| {
+                    // Reference cube to visualize the emit origin
+                    p.spawn()
+                        .insert_bundle(PbrBundle {
+                            mesh: cube.clone(),
+                            material: mat.clone(),
+                            ..Default::default()
+                        })
+                        .insert(Name::new("source"));
+                });
+        }
+    }
+}

run_examples.bat

@@ -8,4 +8,5 @@ cargo r --example spawn_on_command --no-default-features --features="bevy/bevy_w
 cargo r --example activate --no-default-features --features="bevy/bevy_winit bevy/bevy_pbr 3d"
 cargo r --example force_field --no-default-features --features="bevy/bevy_winit bevy/bevy_pbr 3d"
 cargo r --example 2d --no-default-features --features="bevy/bevy_winit bevy/bevy_sprite 2d"
-cargo r --example lifetime --no-default-features --features="bevy/bevy_winit bevy/bevy_pbr 3d"
+cargo r --example lifetime --no-default-features --features="bevy/bevy_winit bevy/bevy_pbr 3d"
+cargo r --example instancing --no-default-features --features="bevy/bevy_winit bevy/bevy_pbr 3d"

src/render/effect_cache.rs

@@ -117,7 +117,11 @@ pub enum BufferState {
 
 impl EffectBuffer {
     /// Minimum buffer capacity to allocate, in number of particles.
-    pub const MIN_CAPACITY: u32 = 65536; // at least 64k particles
+    // FIXME - Batching is broken due to binding a single GpuSpawnerParam instead of N,
+    // and inability for a particle index to tell which Spawner it should use. Setting
+    // this to 1 effectively ensures that all new buffers just fit the effect, so batching
+    // never occurs.
+    pub const MIN_CAPACITY: u32 = 1; //65536; // at least 64k particles
 
     /// Create a new group and a GPU buffer to back it up.
     ///

src/render/mod.rs

@@ -1396,6 +1396,7 @@ pub(crate) fn queue_effects(
             resource: BindingResource::Buffer(BufferBinding {
                 buffer: effects_meta.spawner_buffer.buffer().unwrap(),
                 offset: 0,
+                // TODO - should bind N consecutive structs for batching
                 size: Some(GpuSpawnerParams::min_size()),
             }),
         }],
@@ -1980,14 +1981,16 @@ impl Node for ParticleUpdateNode {
                         assert!(
                             spawner_buffer_aligned >= GpuSpawnerParams::min_size().get() as usize
                         );
+                        let spawner_offset = spawner_base * spawner_buffer_aligned as u32;
 
                         trace!(
-                            "record commands for pipeline of effect {:?} ({} items / {}B/item = {} workgroups) spawner_base={} buffer_offset={}...",
+                            "record commands for pipeline of effect {:?} ({} items / {}B/item = {} workgroups) spawner_base={} spawner_offset={} buffer_offset={}...",
                             batch.handle,
                             item_count,
                             item_size,
                             workgroup_count,
                             spawner_base,
+                            spawner_offset,
                             buffer_offset,
                         );
 
@@ -2007,7 +2010,7 @@ impl Node for ParticleUpdateNode {
                         compute_pass.set_bind_group(
                             2,
                             effects_meta.spawner_bind_group.as_ref().unwrap(),
-                            &[spawner_base * spawner_buffer_aligned as u32],
+                            &[spawner_offset],
                         );
                         compute_pass.dispatch_workgroups(workgroup_count, 1, 1);
                         trace!("compute dispatched");