Fix point lights not despawning (#19)

* Revert "Use custom point light preparation (#17)"

This reverts commit 2ae0336.

* Write "empty" point light to render world

GpuArrayBuffer won't write to the GPU if we have no point lights (an
empty array).

We first tried writing a more custom integration with the GPU, but ended
up running into a very similar problem.

For now lets use GPUArrayBuffer and all it does for us, writing an "empty"
point light to ensure we'll always have a binding.

* Update changelog

CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Fixed
+
+- Point lights not despawning (#19).
+
 ## [0.2.1] - 2024-07-19
 
 ### Fixed

src/plugin.rs

@@ -6,9 +6,9 @@ use bevy::{
     prelude::*,
     render::{
         extract_component::UniformComponentPlugin,
+        gpu_component_array_buffer::GpuComponentArrayBufferPlugin,
         render_graph::{RenderGraphApp, ViewNodeRunner},
         render_resource::SpecializedRenderPipelines,
-        renderer::RenderDevice,
         view::{check_visibility, VisibilitySystems},
         Render, RenderApp, RenderSet,
     },
@@ -17,12 +17,14 @@ use bevy::{
 use crate::{
     light::{AmbientLight2d, PointLight2d},
     render::{
-        extract::{extract_ambient_lights, extract_point_lights, ExtractedAmbientLight2d},
+        extract::{
+            extract_ambient_lights, extract_point_lights, ExtractedAmbientLight2d,
+            ExtractedPointLight2d,
+        },
         lighting::{
             prepare_lighting_pipelines, LightingNode, LightingPass, LightingPipeline,
             LIGHTING_SHADER,
         },
-        prepare::{prepare_point_lights, GpuPointLights},
     },
 };
 
@@ -38,13 +40,16 @@ impl Plugin for Light2dPlugin {
             Shader::from_wgsl
         );
 
-        app.add_plugins(UniformComponentPlugin::<ExtractedAmbientLight2d>::default())
-            .register_type::<AmbientLight2d>()
-            .register_type::<PointLight2d>()
-            .add_systems(
-                PostUpdate,
-                check_visibility::<With<PointLight2d>>.in_set(VisibilitySystems::CheckVisibility),
-            );
+        app.add_plugins((
+            UniformComponentPlugin::<ExtractedAmbientLight2d>::default(),
+            GpuComponentArrayBufferPlugin::<ExtractedPointLight2d>::default(),
+        ))
+        .register_type::<AmbientLight2d>()
+        .register_type::<PointLight2d>()
+        .add_systems(
+            PostUpdate,
+            check_visibility::<With<PointLight2d>>.in_set(VisibilitySystems::CheckVisibility),
+        );
 
         let Some(render_app) = app.get_sub_app_mut(RenderApp) else {
             return;
@@ -60,10 +65,6 @@ impl Plugin for Light2dPlugin {
                 Render,
                 prepare_lighting_pipelines.in_set(RenderSet::Prepare),
             )
-            .add_systems(
-                Render,
-                prepare_point_lights.in_set(RenderSet::PrepareResources),
-            )
             .add_render_graph_node::<ViewNodeRunner<LightingNode>>(Core2d, LightingPass)
             .add_render_graph_edge(Core2d, Node2d::EndMainPass, LightingPass);
     }
@@ -74,9 +75,5 @@ impl Plugin for Light2dPlugin {
         };
 
         render_app.init_resource::<LightingPipeline>();
-
-        render_app.insert_resource(GpuPointLights::new(
-            render_app.world().resource::<RenderDevice>(),
-        ));
     }
 }

src/render/extract.rs

@@ -5,7 +5,7 @@ use bevy::{
 
 use crate::light::{AmbientLight2d, PointLight2d};
 
-#[derive(Component, Default, Clone, ShaderType, Copy)]
+#[derive(Component, Default, Clone, ShaderType)]
 pub struct ExtractedPointLight2d {
     pub transform: Vec2,
     pub radius: f32,
@@ -35,6 +35,16 @@ pub fn extract_point_lights(
             falloff: point_light.falloff,
         });
     }
+
+    // BufferVec won't write to the GPU if there aren't any point lights.
+    // For now we can spawn an empty point light to get around this.
+    commands.spawn(ExtractedPointLight2d {
+        transform: Vec2::ZERO,
+        intensity: 0.0,
+        radius: 0.0,
+        falloff: 0.0,
+        color: LinearRgba::BLACK,
+    });
 }
 
 pub fn extract_ambient_lights(

src/render/lighting/node.rs

@@ -3,14 +3,14 @@ use bevy::render::extract_component::{ComponentUniforms, DynamicUniformIndex};
 use bevy::render::render_graph::ViewNode;
 
 use bevy::render::render_resource::{
-    BindGroupEntries, Operations, PipelineCache, RenderPassColorAttachment, RenderPassDescriptor,
+    BindGroupEntries, GpuArrayBuffer, Operations, PipelineCache, RenderPassColorAttachment,
+    RenderPassDescriptor,
 };
 use bevy::render::renderer::RenderDevice;
 use bevy::render::view::{ViewTarget, ViewUniformOffset, ViewUniforms};
 use smallvec::{smallvec, SmallVec};
 
-use crate::render::extract::ExtractedAmbientLight2d;
-use crate::render::prepare::GpuPointLights;
+use crate::render::extract::{ExtractedAmbientLight2d, ExtractedPointLight2d};
 
 use super::{LightingPipeline, LightingPipelineId};
 
@@ -58,7 +58,10 @@ impl ViewNode for LightingNode {
             return Ok(());
         };
 
-        let Some(point_light_binding) = world.resource::<GpuPointLights>().binding() else {
+        let Some(point_light_binding) = world
+            .resource::<GpuArrayBuffer<ExtractedPointLight2d>>()
+            .binding()
+        else {
             return Ok(());
         };
 

src/render/mod.rs

@@ -1,3 +1,2 @@
 pub mod extract;
 pub mod lighting;
-pub mod prepare;