clean up

Cargo.toml

@@ -85,6 +85,8 @@ bevy_gltf = ["bevy_internal/bevy_gltf", "bevy_asset", "bevy_scene", "bevy_pbr"]
 # Adds PBR rendering
 bevy_pbr = ["bevy_internal/bevy_pbr", "bevy_asset", "bevy_render", "bevy_core_pipeline"]
 
+gpu_picking = []
+
 # Provides rendering functionality
 bevy_render = ["bevy_internal/bevy_render"]
 

crates/bevy_core_pipeline/src/core_3d/mod.rs

@@ -86,6 +86,7 @@ impl Plugin for Core3dPlugin {
                     prepare_core_3d_depth_textures
                         .in_set(RenderSet::Prepare)
                         .after(bevy_render::view::prepare_windows),
+                    // #[cfg(feature = "gpu_picking")]
                     prepare_entity_textures
                         .in_set(RenderSet::Prepare)
                         .after(bevy_render::view::prepare_windows),

crates/bevy_core_pipeline/src/entity_index_buffer_copy/mod.rs

@@ -25,11 +25,9 @@ impl ViewNode for EntityIndexBufferCopyNode {
             return Ok(());
         };
 
-        // copy entity index texture
         buffers.copy_texture_to_buffer(
             render_context.command_encoder(),
             &entity_index_textures.main.texture,
-            &buffers.entity_buffer,
         );
 
         Ok(())

crates/bevy_gizmos/src/lib.rs

@@ -37,14 +37,16 @@ use bevy_reflect::{
 use bevy_render::{
     color::Color,
     mesh::Mesh,
-    picking,
     primitives::Aabb,
     render_phase::AddRenderCommand,
     render_resource::{PrimitiveTopology, Shader, SpecializedMeshPipelines},
     Extract, ExtractSchedule, Render, RenderApp, RenderSet,
 };
 use bevy_transform::components::{GlobalTransform, Transform};
 
+// #[cfg(feature = "gpu_picking")]
+use bevy_render::picking;
+
 #[cfg(feature = "bevy_pbr")]
 use bevy_pbr::MeshUniform;
 #[cfg(feature = "bevy_sprite")]
@@ -326,6 +328,7 @@ fn extract_gizmo_data(
                             transform,
                             previous_transform: transform,
                             inverse_transpose_model,
+                            // #[cfg(feature = "gpu_picking")]
                             entity: picking::entity_as_uvec2(Entity::PLACEHOLDER),
                         },
                     ),

crates/bevy_pbr/Cargo.toml

@@ -10,6 +10,7 @@ keywords = ["bevy"]
 
 [features]
 webgl = []
+gpu_picking = []
 
 [dependencies]
 # bevy

crates/bevy_pbr/src/render/mesh.rs

@@ -132,7 +132,7 @@ pub struct MeshUniform {
     pub transform: Mat4,
     pub previous_transform: Mat4,
     pub inverse_transpose_model: Mat4,
-    // TODO should probably be a separate uniform in case gpu picking is disabled
+    // #[cfg(feature = "gpu_picking")]
     pub entity: UVec2,
     pub flags: u32,
 }
@@ -187,6 +187,7 @@ pub fn extract_meshes(
             flags: flags.bits(),
             transform,
             previous_transform,
+            // #[cfg(feature = "gpu_picking")]
             entity: picking::entity_as_uvec2(entity),
             inverse_transpose_model: transform.inverse().transpose(),
         };

crates/bevy_render/src/lib.rs

@@ -45,7 +45,6 @@ pub mod prelude {
 use bevy_window::{PrimaryWindow, RawHandleWrapper};
 use globals::GlobalsPlugin;
 pub use once_cell;
-use picking::GpuPickingPlugin;
 use renderer::{RenderAdapter, RenderAdapterInfo, RenderDevice, RenderQueue};
 use wgpu::Instance;
 
@@ -336,8 +335,7 @@ impl Plugin for RenderPlugin {
             .add_plugin(CameraPlugin)
             .add_plugin(ViewPlugin)
             .add_plugin(MeshPlugin)
-            .add_plugin(GlobalsPlugin)
-            .add_plugin(GpuPickingPlugin);
+            .add_plugin(GlobalsPlugin);
 
         app.register_type::<color::Color>()
             .register_type::<primitives::Aabb>()

crates/bevy_render/src/picking.rs

@@ -1,132 +1,106 @@
 use crate::{
     camera::ExtractedCamera,
     extract_component::ExtractComponentPlugin,
-    render_resource::{Buffer, BufferSlice, Texture},
+    render_resource::{Buffer, Texture},
     renderer::RenderDevice,
     texture::{CachedTexture, TextureFormatPixelInfo},
     Render, RenderApp, RenderSet,
 };
-use async_channel::{Receiver, Sender, TrySendError};
+use async_channel::{Receiver, Sender};
 use bevy_app::{Plugin, Update};
 use bevy_ecs::prelude::*;
 
 use bevy_math::UVec2;
 use bevy_render_macros::ExtractComponent;
 use bevy_tasks::AsyncComputeTaskPool;
-use bevy_utils::{default, HashMap};
+use bevy_utils::default;
 use wgpu::{
-    BufferDescriptor, BufferUsages, Color, CommandEncoder, Extent3d, ImageDataLayout, Maintain,
-    MapMode, Operations, RenderPassColorAttachment, TextureFormat,
+    BufferDescriptor, BufferUsages, Color, CommandEncoder, Extent3d, ImageDataLayout, MapMode,
+    Operations, RenderPassColorAttachment, TextureFormat,
 };
 
 pub const ENTITY_TEXTURE_FORMAT: TextureFormat = TextureFormat::Rg32Uint;
 
+/// This plugin enables the gpu picking feature of bevy.
+///
+/// Gpu picking let's you know which entity is currently under the mouse.
+///
+/// # How this works:
+///
+/// - For each entity being rendered, it will output it's entity id to a texture.
+/// - Once everything is rendered it will copy that texture to the cpu and send it to the main world
+/// - From the main world you can give it a position like the current mouse position and
+///   know exactly which entity was rendered at that specific screen location.
+/// - This works at the [`Camera`] level, so it will work with multiple windows or split screen
+///
+/// # Api Overview:
+///
+/// You need to add the [`GpuPickingCamera`] to any `Camera` that will be used for picking.
+/// Then add the [`GpuPickingMesh`] comnponent to any `Mesh` that will need to be picked.
+///
+/// Once those components are added, you can query for [`GpuPickingCamera`]
+/// and use `GpuPickingCamera::get_entity(position)` to know which entity is at the given position on screen
 pub struct GpuPickingPlugin;
 impl Plugin for GpuPickingPlugin {
     fn build(&self, app: &mut bevy_app::App) {
         app.add_plugin(ExtractComponentPlugin::<GpuPickingMesh>::default())
             .add_plugin(ExtractComponentPlugin::<GpuPickingCamera>::default())
-            .add_systems(Update, update_entity_buffer);
+            .add_systems(Update, receive_buffer);
 
         let Ok(render_app) = app.get_sub_app_mut(RenderApp) else { return; };
 
         render_app.add_systems(
             Render,
             (
                 prepare_gpu_picking_buffers.in_set(RenderSet::Prepare),
-                send_buffer_to_main_world.in_set(RenderSet::RenderFlush),
+                map_and_send_buffer_async.in_set(RenderSet::RenderFlush),
             ),
         );
     }
 }
 
-/// Copies the entity buffer to the cpu and sends it to the main world
-fn send_buffer_to_main_world(
-    query: Query<&ExtractedGpuPickingCamera, With<ExtractedCamera>>,
-    render_device: Res<RenderDevice>,
-) {
+/// Maps the entity buffer and sends it to the main world asynchronously
+fn map_and_send_buffer_async(query: Query<&ExtractedGpuPickingCamera, With<ExtractedCamera>>) {
     for gpu_picking_camera in &query {
         let Some(buffers) = gpu_picking_camera.buffers.as_ref() else {
             return;
         };
+        let buffers = buffers.clone();
+        let sender = gpu_picking_camera.sender.clone();
 
-        // Send the data to the main world
-        fn send(
-            sender: Sender<GpuPickingData>,
-            padded_bytes_per_row: usize,
-            entity_buffer: &Buffer,
-            buffer_slice: BufferSlice,
-        ) {
-            let buffer_view = buffer_slice.get_mapped_range();
-            // immediately copy the data to CPU to avoid holding the mapped view for long
-            let entity_data = Vec::from(&*buffer_view);
-            drop(buffer_view);
-            entity_buffer.unmap();
+        // Mapping the buffer is an asynchronous process.
+        // This means we need to wait until the buffer is mapped before sending it to the main world
+        let task = async move {
+            let (tx, rx) = async_channel::bounded(1);
 
-            if let Err(err) = sender.try_send(GpuPickingData {
-                padded_bytes_per_row,
-                entity_data,
-            }) {
-                match err {
-                    TrySendError::Full(_) => bevy_log::error!("GPU Picking channel is full"),
-                    TrySendError::Closed(_) => {
-                        bevy_log::error!("GPU Picking channel is closed");
-                    }
-                }
-            }
-
-            // This can only fail if the sender is full or closed
-            // and we can't do anything if either of those things happen
-            // let _ = sender.try_send(GpuPickingData {
-            //     padded_bytes_per_row,
-            //     entity_data,
-            // });
-        }
-
-        if true {
-            // sync
+            // map entity buffer
             let buffer_slice = buffers.entity_buffer.slice(..);
             buffer_slice.map_async(MapMode::Read, move |result| match result {
-                Ok(_) => {}
+                Ok(_) => tx.try_send(()).unwrap(),
                 Err(err) => bevy_log::error!("Failed to map entity buffer: {err}"),
             });
 
-            // WARN This is blocking
-            render_device.poll(Maintain::Wait);
+            // Buffer is mapped and ready to be sent
+            rx.recv().await.unwrap();
 
             // Send the buffer to the main world
-            send(
-                gpu_picking_camera.sender.clone(),
-                buffers.buffer_dimensions.padded_bytes_per_row,
-                &buffers.entity_buffer,
-                buffer_slice,
-            );
-        } else {
-            // async
-            let entity_buffer = buffers.entity_buffer.clone();
-            let sender = gpu_picking_camera.sender.clone();
-            let padded_bytes_per_row = buffers.buffer_dimensions.padded_bytes_per_row;
-
-            // Mapping the buffer is an asynchronous process.
-            // This means we need to wait until the buffer is mapped before sending it to the main world
-            let task = async move {
-                let (tx, rx) = async_channel::bounded(1);
-
-                // map entity buffer
-                let buffer_slice = entity_buffer.slice(..);
-                buffer_slice.map_async(MapMode::Read, move |result| match result {
-                    Ok(_) => tx.try_send(()).unwrap(),
-                    Err(err) => bevy_log::error!("Failed to map entity buffer: {err}"),
-                });
-
-                // Buffer is mapped and ready to be sent
-                rx.recv().await.unwrap();
-
-                // Send the buffer to the main world
-                send(sender, padded_bytes_per_row, &entity_buffer, buffer_slice);
-            };
-            AsyncComputeTaskPool::get().spawn(task).detach();
-        }
+            let entity_buffer = &buffers.entity_buffer;
+            let buffer_view = buffer_slice.get_mapped_range();
+            // immediately copy the data to CPU to avoid holding the mapped view for long
+            let entity_data = Vec::from(&*buffer_view);
+            drop(buffer_view);
+            entity_buffer.unmap();
+
+            // Because the channel is bounded to 1 entry, it's pretty common to have the channel full.
+            // This isn't ideal but not blocking makes it faster which is preferred.
+            //
+            // The other possible error is for the channel to be closed and in that case we can't do anything
+            let _ = sender.try_send(GpuPickingData {
+                padded_bytes_per_row: buffers.buffer_dimensions.padded_bytes_per_row,
+                entity_data,
+            });
+        };
+        AsyncComputeTaskPool::get().spawn(task).detach();
     }
 }
 
@@ -166,7 +140,7 @@ impl Default for GpuPickingCamera {
 impl GpuPickingCamera {
     pub fn new() -> Self {
         Self {
-            channel: async_channel::unbounded(),
+            channel: async_channel::bounded(1),
             data: GpuPickingData::default(),
         }
     }
@@ -218,24 +192,21 @@ impl crate::extract_component::ExtractComponent for GpuPickingCamera {
 }
 
 /// Contains the buffer and it's dimension required for gpu picking
+#[derive(Clone)]
 pub struct GpuPickingCameraBuffers {
     pub entity_buffer: Buffer,
     buffer_dimensions: BufferDimensions,
 }
 
 impl GpuPickingCameraBuffers {
-    pub fn copy_texture_to_buffer(
-        &self,
-        encoder: &mut CommandEncoder,
-        texture: &Texture,
-        buffer: &Buffer,
-    ) {
+    /// Copies the given texture to the entity buffer
+    pub fn copy_texture_to_buffer(&self, encoder: &mut CommandEncoder, texture: &Texture) {
         // This can't be in the Node because it needs access to wgpu but
         // bevy_core_pipeline doesn't depend on wgpu
         encoder.copy_texture_to_buffer(
             texture.as_image_copy(),
             wgpu::ImageCopyBuffer {
-                buffer,
+                buffer: &self.entity_buffer,
                 layout: ImageDataLayout {
                     offset: 0,
                     bytes_per_row: Some(self.buffer_dimensions.padded_bytes_per_row as u32),
@@ -251,16 +222,11 @@ impl GpuPickingCameraBuffers {
     }
 }
 
-fn update_entity_buffer(mut q: Query<&mut GpuPickingCamera>) {
+fn receive_buffer(mut q: Query<&mut GpuPickingCamera>) {
     for mut cam in &mut q {
         let (_, receiver) = cam.channel.clone();
-        loop {
-            let Ok(buffer) = receiver.try_recv() else { break; };
-            if receiver.is_empty() {
-                cam.data = buffer;
-                break;
-            }
-        }
+        let Ok(data) = receiver.try_recv() else { continue; };
+        cam.data = data;
     }
 }
 
@@ -316,39 +282,25 @@ impl EntityTextures {
 fn prepare_gpu_picking_buffers(
     render_device: Res<RenderDevice>,
     mut cameras: Query<
-        (Entity, &ExtractedCamera, &mut ExtractedGpuPickingCamera),
+        (&ExtractedCamera, &mut ExtractedGpuPickingCamera),
         Changed<ExtractedCamera>,
     >,
-    mut buffer_cache: Local<HashMap<Entity, (BufferDimensions, Buffer)>>,
 ) {
-    for (entity, camera, mut gpu_picking_camera) in &mut cameras {
+    for (camera, mut gpu_picking_camera) in &mut cameras {
         let Some(size) = camera.physical_target_size else { continue; };
 
-        // TODO create 2 buffers and altenate between each buffer each frame
-
-        // Only create a buffer if it doesn't already exist or the size is different
-        let mut create_buffer = true;
-        if let Some((buffer_dimensions, _)) = buffer_cache.get(&entity) {
-            create_buffer = buffer_dimensions.width != size.x as usize
-                || buffer_dimensions.height != size.y as usize;
-        }
-
-        if create_buffer {
-            let buffer_dimensions =
-                BufferDimensions::new(size.x as usize, size.y as usize, ENTITY_TEXTURE_FORMAT);
-            let entity_buffer = render_device.create_buffer(&BufferDescriptor {
-                label: Some("Entity Buffer"),
-                size: (buffer_dimensions.padded_bytes_per_row * buffer_dimensions.height) as u64,
-                usage: BufferUsages::COPY_DST | BufferUsages::MAP_READ,
-                mapped_at_creation: false,
-            });
-            buffer_cache.insert(entity, (buffer_dimensions, entity_buffer));
-        }
+        let buffer_dimensions =
+            BufferDimensions::new(size.x as usize, size.y as usize, ENTITY_TEXTURE_FORMAT);
+        let entity_buffer = render_device.create_buffer(&BufferDescriptor {
+            label: Some("Entity Buffer"),
+            size: (buffer_dimensions.padded_bytes_per_row * buffer_dimensions.height) as u64,
+            usage: BufferUsages::COPY_DST | BufferUsages::MAP_READ,
+            mapped_at_creation: false,
+        });
 
-        let Some((buffer_dimensions, entity_buffer)) = buffer_cache.get(&entity) else { continue; };
         gpu_picking_camera.buffers = Some(GpuPickingCameraBuffers {
             entity_buffer: entity_buffer.clone(),
-            buffer_dimensions: *buffer_dimensions,
+            buffer_dimensions,
         });
     }
 }