Support Warning

WebGPU is currently only supported on Chrome starting with version 113, and only on desktop. If they don't work on your configuration, you can check the WebGL2 examples here.

//! A shader that renders a mesh multiple times in one draw call.

use bevy::{
    core_pipeline::core_3d::Transparent3d,
    ecs::{
        query::QueryItem,
        system::{lifetimeless::*, SystemParamItem},
    },
    pbr::{
        MeshPipeline, MeshPipelineKey, RenderMeshInstances, SetMeshBindGroup, SetMeshViewBindGroup,
    },
    prelude::*,
    render::{
        extract_component::{ExtractComponent, ExtractComponentPlugin},
        mesh::{GpuBufferInfo, MeshVertexBufferLayout},
        render_asset::RenderAssets,
        render_phase::{
            AddRenderCommand, DrawFunctions, PhaseItem, RenderCommand, RenderCommandResult,
            RenderPhase, SetItemPipeline, TrackedRenderPass,
        },
        render_resource::*,
        renderer::RenderDevice,
        view::{ExtractedView, NoFrustumCulling},
        Render, RenderApp, RenderSet,
    },
};
use bytemuck::{Pod, Zeroable};

fn main() {
    App::new()
        .add_plugins((DefaultPlugins, CustomMaterialPlugin))
        .add_systems(Startup, setup)
        .run();
}

fn setup(mut commands: Commands, mut meshes: ResMut<Assets<Mesh>>) {
    commands.spawn((
        meshes.add(Cuboid::new(0.5, 0.5, 0.5)),
        SpatialBundle::INHERITED_IDENTITY,
        InstanceMaterialData(
            (1..=10)
                .flat_map(|x| (1..=10).map(move |y| (x as f32 / 10.0, y as f32 / 10.0)))
                .map(|(x, y)| InstanceData {
                    position: Vec3::new(x * 10.0 - 5.0, y * 10.0 - 5.0, 0.0),
                    scale: 1.0,
                    color: Color::hsla(x * 360., y, 0.5, 1.0).as_rgba_f32(),
                })
                .collect(),
        ),
        // NOTE: Frustum culling is done based on the Aabb of the Mesh and the GlobalTransform.
        // As the cube is at the origin, if its Aabb moves outside the view frustum, all the
        // instanced cubes will be culled.
        // The InstanceMaterialData contains the 'GlobalTransform' information for this custom
        // instancing, and that is not taken into account with the built-in frustum culling.
        // We must disable the built-in frustum culling by adding the `NoFrustumCulling` marker
        // component to avoid incorrect culling.
        NoFrustumCulling,
    ));

    // camera
    commands.spawn(Camera3dBundle {
        transform: Transform::from_xyz(0.0, 0.0, 15.0).looking_at(Vec3::ZERO, Vec3::Y),
        ..default()
    });
}

#[derive(Component, Deref)]
struct InstanceMaterialData(Vec<InstanceData>);

impl ExtractComponent for InstanceMaterialData {
    type QueryData = &'static InstanceMaterialData;
    type QueryFilter = ();
    type Out = Self;

    fn extract_component(item: QueryItem<'_, Self::QueryData>) -> Option<Self> {
        Some(InstanceMaterialData(item.0.clone()))
    }
}

struct CustomMaterialPlugin;

impl Plugin for CustomMaterialPlugin {
    fn build(&self, app: &mut App) {
        app.add_plugins(ExtractComponentPlugin::<InstanceMaterialData>::default());
        app.sub_app_mut(RenderApp)
            .add_render_command::<Transparent3d, DrawCustom>()
            .init_resource::<SpecializedMeshPipelines<CustomPipeline>>()
            .add_systems(
                Render,
                (
                    queue_custom.in_set(RenderSet::QueueMeshes),
                    prepare_instance_buffers.in_set(RenderSet::PrepareResources),
                ),
            );
    }

    fn finish(&self, app: &mut App) {
        app.sub_app_mut(RenderApp).init_resource::<CustomPipeline>();
    }
}

#[derive(Clone, Copy, Pod, Zeroable)]
#[repr(C)]
struct InstanceData {
    position: Vec3,
    scale: f32,
    color: [f32; 4],
}

#[allow(clippy::too_many_arguments)]
fn queue_custom(
    transparent_3d_draw_functions: Res<DrawFunctions<Transparent3d>>,
    custom_pipeline: Res<CustomPipeline>,
    msaa: Res<Msaa>,
    mut pipelines: ResMut<SpecializedMeshPipelines<CustomPipeline>>,
    pipeline_cache: Res<PipelineCache>,
    meshes: Res<RenderAssets<Mesh>>,
    render_mesh_instances: Res<RenderMeshInstances>,
    material_meshes: Query<Entity, With<InstanceMaterialData>>,
    mut views: Query<(&ExtractedView, &mut RenderPhase<Transparent3d>)>,
) {
    let draw_custom = transparent_3d_draw_functions.read().id::<DrawCustom>();

    let msaa_key = MeshPipelineKey::from_msaa_samples(msaa.samples());

    for (view, mut transparent_phase) in &mut views {
        let view_key = msaa_key | MeshPipelineKey::from_hdr(view.hdr);
        let rangefinder = view.rangefinder3d();
        for entity in &material_meshes {
            let Some(mesh_instance) = render_mesh_instances.get(&entity) else {
                continue;
            };
            let Some(mesh) = meshes.get(mesh_instance.mesh_asset_id) else {
                continue;
            };
            let key = view_key | MeshPipelineKey::from_primitive_topology(mesh.primitive_topology);
            let pipeline = pipelines
                .specialize(&pipeline_cache, &custom_pipeline, key, &mesh.layout)
                .unwrap();
            transparent_phase.add(Transparent3d {
                entity,
                pipeline,
                draw_function: draw_custom,
                distance: rangefinder
                    .distance_translation(&mesh_instance.transforms.transform.translation),
                batch_range: 0..1,
                dynamic_offset: None,
            });
        }
    }
}

#[derive(Component)]
struct InstanceBuffer {
    buffer: Buffer,
    length: usize,
}

fn prepare_instance_buffers(
    mut commands: Commands,
    query: Query<(Entity, &InstanceMaterialData)>,
    render_device: Res<RenderDevice>,
) {
    for (entity, instance_data) in &query {
        let buffer = render_device.create_buffer_with_data(&BufferInitDescriptor {
            label: Some("instance data buffer"),
            contents: bytemuck::cast_slice(instance_data.as_slice()),
            usage: BufferUsages::VERTEX | BufferUsages::COPY_DST,
        });
        commands.entity(entity).insert(InstanceBuffer {
            buffer,
            length: instance_data.len(),
        });
    }
}

#[derive(Resource)]
struct CustomPipeline {
    shader: Handle<Shader>,
    mesh_pipeline: MeshPipeline,
}

impl FromWorld for CustomPipeline {
    fn from_world(world: &mut World) -> Self {
        let asset_server = world.resource::<AssetServer>();
        let shader = asset_server.load("shaders/instancing.wgsl");

        let mesh_pipeline = world.resource::<MeshPipeline>();

        CustomPipeline {
            shader,
            mesh_pipeline: mesh_pipeline.clone(),
        }
    }
}

impl SpecializedMeshPipeline for CustomPipeline {
    type Key = MeshPipelineKey;

    fn specialize(
        &self,
        key: Self::Key,
        layout: &MeshVertexBufferLayout,
    ) -> Result<RenderPipelineDescriptor, SpecializedMeshPipelineError> {
        let mut descriptor = self.mesh_pipeline.specialize(key, layout)?;

        descriptor.vertex.shader = self.shader.clone();
        descriptor.vertex.buffers.push(VertexBufferLayout {
            array_stride: std::mem::size_of::<InstanceData>() as u64,
            step_mode: VertexStepMode::Instance,
            attributes: vec![
                VertexAttribute {
                    format: VertexFormat::Float32x4,
                    offset: 0,
                    shader_location: 3, // shader locations 0-2 are taken up by Position, Normal and UV attributes
                },
                VertexAttribute {
                    format: VertexFormat::Float32x4,
                    offset: VertexFormat::Float32x4.size(),
                    shader_location: 4,
                },
            ],
        });
        descriptor.fragment.as_mut().unwrap().shader = self.shader.clone();
        Ok(descriptor)
    }
}

type DrawCustom = (
    SetItemPipeline,
    SetMeshViewBindGroup<0>,
    SetMeshBindGroup<1>,
    DrawMeshInstanced,
);

struct DrawMeshInstanced;

impl<P: PhaseItem> RenderCommand<P> for DrawMeshInstanced {
    type Param = (SRes<RenderAssets<Mesh>>, SRes<RenderMeshInstances>);
    type ViewQuery = ();
    type ItemQuery = Read<InstanceBuffer>;

    #[inline]
    fn render<'w>(
        item: &P,
        _view: (),
        instance_buffer: Option<&'w InstanceBuffer>,
        (meshes, render_mesh_instances): SystemParamItem<'w, '_, Self::Param>,
        pass: &mut TrackedRenderPass<'w>,
    ) -> RenderCommandResult {
        let Some(mesh_instance) = render_mesh_instances.get(&item.entity()) else {
            return RenderCommandResult::Failure;
        };
        let Some(gpu_mesh) = meshes.into_inner().get(mesh_instance.mesh_asset_id) else {
            return RenderCommandResult::Failure;
        };
        let Some(instance_buffer) = instance_buffer else {
            return RenderCommandResult::Failure;
        };

        pass.set_vertex_buffer(0, gpu_mesh.vertex_buffer.slice(..));
        pass.set_vertex_buffer(1, instance_buffer.buffer.slice(..));

        match &gpu_mesh.buffer_info {
            GpuBufferInfo::Indexed {
                buffer,
                index_format,
                count,
            } => {
                pass.set_index_buffer(buffer.slice(..), 0, *index_format);
                pass.draw_indexed(0..*count, 0, 0..instance_buffer.length as u32);
            }
            GpuBufferInfo::NonIndexed => {
                pass.draw(0..gpu_mesh.vertex_count, 0..instance_buffer.length as u32);
            }
        }
        RenderCommandResult::Success
    }
}