Add 2d meshes and materials (#3460)

# Objective

The current 2d rendering is specialized to render sprites, we need a generic way to render 2d items, using meshes and materials like we have for 3d.

## Solution

I cloned a good part of `bevy_pbr` into `bevy_sprite/src/mesh2d`, removed lighting and pbr itself, adapted it to 2d rendering, added a `ColorMaterial`, and modified the sprite rendering to break batches around 2d meshes.

~~The PR is a bit crude; I tried to change as little as I could in both the parts copied from 3d and the current sprite rendering to make reviewing easier. In the future, I expect we could make the sprite rendering a normal 2d material, cleanly integrated with the rest.~~ _edit: see <https://github.com/bevyengine/bevy/pull/3460#issuecomment-1003605194>_

## Remaining work

- ~~don't require mesh normals~~ _out of scope_
- ~~add an example~~ _done_
- support 2d meshes & materials in the UI?
- bikeshed names (I didn't think hard about naming, please check if it's fine)

## Remaining questions

- ~~should we add a depth buffer to 2d now that there are 2d meshes?~~ _let's revisit that when we have an opaque render phase_
- ~~should we add MSAA support to the sprites, or remove it from the 2d meshes?~~ _I added MSAA to sprites since it's really needed for 2d meshes_
- ~~how to customize vertex attributes?~~ _#3120_



Co-authored-by: Carter Anderson <mcanders1@gmail.com>

Cargo.toml

@@ -119,6 +119,14 @@ path = "examples/2d/contributors.rs"
 name = "many_sprites"
 path = "examples/2d/many_sprites.rs"
 
+[[example]]
+name = "mesh2d"
+path = "examples/2d/mesh2d.rs"
+
+[[example]]
+name = "mesh2d_manual"
+path = "examples/2d/mesh2d_manual.rs"
+
 [[example]]
 name = "rect"
 path = "examples/2d/rect.rs"

crates/bevy_core_pipeline/src/lib.rs

@@ -15,6 +15,8 @@ pub use main_pass_2d::*;
 pub use main_pass_3d::*;
 pub use main_pass_driver::*;
 
+use std::ops::Range;
+
 use bevy_app::{App, Plugin};
 use bevy_core::FloatOrd;
 use bevy_ecs::prelude::*;
@@ -23,8 +25,8 @@ use bevy_render::{
     color::Color,
     render_graph::{EmptyNode, RenderGraph, SlotInfo, SlotType},
     render_phase::{
-        sort_phase_system, CachedPipelinePhaseItem, DrawFunctionId, DrawFunctions, EntityPhaseItem,
-        PhaseItem, RenderPhase,
+        batch_phase_system, sort_phase_system, BatchedPhaseItem, CachedPipelinePhaseItem,
+        DrawFunctionId, DrawFunctions, EntityPhaseItem, PhaseItem, RenderPhase,
     },
     render_resource::*,
     renderer::RenderDevice,
@@ -84,6 +86,11 @@ pub mod clear_graph {
 #[derive(Default)]
 pub struct CorePipelinePlugin;
 
+#[derive(Debug, Hash, PartialEq, Eq, Clone, SystemLabel)]
+pub enum CorePipelineRenderSystems {
+    SortTransparent2d,
+}
+
 impl Plugin for CorePipelinePlugin {
     fn build(&self, app: &mut App) {
         app.init_resource::<ClearColor>();
@@ -97,7 +104,16 @@ impl Plugin for CorePipelinePlugin {
             .add_system_to_stage(RenderStage::Extract, extract_clear_color)
             .add_system_to_stage(RenderStage::Extract, extract_core_pipeline_camera_phases)
             .add_system_to_stage(RenderStage::Prepare, prepare_core_views_system)
-            .add_system_to_stage(RenderStage::PhaseSort, sort_phase_system::<Transparent2d>)
+            .add_system_to_stage(
+                RenderStage::PhaseSort,
+                sort_phase_system::<Transparent2d>
+                    .label(CorePipelineRenderSystems::SortTransparent2d),
+            )
+            .add_system_to_stage(
+                RenderStage::PhaseSort,
+                batch_phase_system::<Transparent2d>
+                    .after(CorePipelineRenderSystems::SortTransparent2d),
+            )
             .add_system_to_stage(RenderStage::PhaseSort, sort_phase_system::<Opaque3d>)
             .add_system_to_stage(RenderStage::PhaseSort, sort_phase_system::<AlphaMask3d>)
             .add_system_to_stage(RenderStage::PhaseSort, sort_phase_system::<Transparent3d>);
@@ -160,6 +176,8 @@ pub struct Transparent2d {
     pub entity: Entity,
     pub pipeline: CachedPipelineId,
     pub draw_function: DrawFunctionId,
+    /// Range in the vertex buffer of this item
+    pub batch_range: Option<Range<u32>>,
 }
 
 impl PhaseItem for Transparent2d {
@@ -176,6 +194,30 @@ impl PhaseItem for Transparent2d {
     }
 }
 
+impl EntityPhaseItem for Transparent2d {
+    #[inline]
+    fn entity(&self) -> Entity {
+        self.entity
+    }
+}
+
+impl CachedPipelinePhaseItem for Transparent2d {
+    #[inline]
+    fn cached_pipeline(&self) -> CachedPipelineId {
+        self.pipeline
+    }
+}
+
+impl BatchedPhaseItem for Transparent2d {
+    fn batch_range(&self) -> &Option<Range<u32>> {
+        &self.batch_range
+    }
+
+    fn batch_range_mut(&mut self) -> &mut Option<Range<u32>> {
+        &mut self.batch_range
+    }
+}
+
 pub struct Opaque3d {
     pub distance: f32,
     pub pipeline: CachedPipelineId,

crates/bevy_core_pipeline/src/main_pass_2d.rs

@@ -3,7 +3,7 @@ use bevy_ecs::prelude::*;
 use bevy_render::{
     render_graph::{Node, NodeRunError, RenderGraphContext, SlotInfo, SlotType},
     render_phase::{DrawFunctions, RenderPhase, TrackedRenderPass},
-    render_resource::{LoadOp, Operations, RenderPassColorAttachment, RenderPassDescriptor},
+    render_resource::{LoadOp, Operations, RenderPassDescriptor},
     renderer::RenderContext,
     view::{ExtractedView, ViewTarget},
 };
@@ -46,14 +46,10 @@ impl Node for MainPass2dNode {
 
         let pass_descriptor = RenderPassDescriptor {
             label: Some("main_pass_2d"),
-            color_attachments: &[RenderPassColorAttachment {
-                view: &target.view,
-                resolve_target: None,
-                ops: Operations {
-                    load: LoadOp::Load,
-                    store: true,
-                },
-            }],
+            color_attachments: &[target.get_color_attachment(Operations {
+                load: LoadOp::Load,
+                store: true,
+            })],
             depth_stencil_attachment: None,
         };
 

crates/bevy_pbr/src/render/mesh.rs

@@ -8,7 +8,7 @@ use bevy_ecs::{
     prelude::*,
     system::{lifetimeless::*, SystemParamItem},
 };
-use bevy_math::Mat4;
+use bevy_math::{Mat4, Size};
 use bevy_reflect::TypeUuid;
 use bevy_render::{
     mesh::{GpuBufferInfo, Mesh},
@@ -328,6 +328,10 @@ impl FromWorld for MeshPipeline {
                 texture,
                 texture_view,
                 sampler,
+                size: Size::new(
+                    image.texture_descriptor.size.width as f32,
+                    image.texture_descriptor.size.height as f32,
+                ),
             }
         };
         MeshPipeline {

crates/bevy_render/Cargo.toml

@@ -53,3 +53,4 @@ hex = "0.4.2"
 hexasphere = "6.0.0"
 parking_lot = "0.11.0"
 regex = "1.5"
+copyless = "0.1.5"

crates/bevy_render/src/render_phase/draw.rs

@@ -13,7 +13,7 @@ use bevy_ecs::{
 };
 use bevy_utils::HashMap;
 use parking_lot::{RwLock, RwLockReadGuard, RwLockWriteGuard};
-use std::{any::TypeId, fmt::Debug, hash::Hash};
+use std::{any::TypeId, fmt::Debug, hash::Hash, ops::Range};
 
 /// A draw function which is used to draw a specific [`PhaseItem`].
 ///
@@ -166,6 +166,49 @@ pub trait CachedPipelinePhaseItem: PhaseItem {
     fn cached_pipeline(&self) -> CachedPipelineId;
 }
 
+/// A [`PhaseItem`] that can be batched dynamically.
+///
+/// Batching is an optimization that regroups multiple items in the same vertex buffer
+/// to render them in a single draw call.
+pub trait BatchedPhaseItem: EntityPhaseItem {
+    /// Range in the vertex buffer of this item
+    fn batch_range(&self) -> &Option<Range<u32>>;
+
+    /// Range in the vertex buffer of this item
+    fn batch_range_mut(&mut self) -> &mut Option<Range<u32>>;
+
+    /// Batches another item within this item if they are compatible.
+    /// Items can be batched together if they have the same entity, and consecutive ranges.
+    /// If batching is successful, the `other` item should be discarded from the render pass.
+    #[inline]
+    fn add_to_batch(&mut self, other: &Self) -> BatchResult {
+        let self_entity = self.entity();
+        if let (Some(self_batch_range), Some(other_batch_range)) = (
+            self.batch_range_mut().as_mut(),
+            other.batch_range().as_ref(),
+        ) {
+            // If the items are compatible, join their range into `self`
+            if self_entity == other.entity() {
+                if self_batch_range.end == other_batch_range.start {
+                    self_batch_range.end = other_batch_range.end;
+                    return BatchResult::Success;
+                } else if self_batch_range.start == other_batch_range.end {
+                    self_batch_range.start = other_batch_range.start;
+                    return BatchResult::Success;
+                }
+            }
+        }
+        BatchResult::IncompatibleItems
+    }
+}
+
+pub enum BatchResult {
+    /// The `other` item was batched into `self`
+    Success,
+    /// `self` and `other` cannot be batched together
+    IncompatibleItems,
+}
+
 impl<P: EntityPhaseItem, E: EntityRenderCommand> RenderCommand<P> for E {
     type Param = E::Param;