mesh.rs

use crate::{
    GlobalLightMeta, GpuLights, GpuPointLights, LightMeta, NotShadowCaster, NotShadowReceiver,
    ShadowPipeline, ViewClusterBindings, ViewLightsUniformOffset, ViewShadowBindings,
    CLUSTERED_FORWARD_STORAGE_BUFFER_COUNT,
};
use bevy_app::Plugin;
use bevy_asset::{load_internal_asset, Assets, Handle, HandleUntyped};
use bevy_ecs::{
    prelude::*,
    system::{lifetimeless::*, SystemParamItem, SystemState},
};
use bevy_math::{Mat4, Vec2};
use bevy_reflect::TypeUuid;
use bevy_render::{
    extract_component::{ComponentUniforms, DynamicUniformIndex, UniformComponentPlugin},
    mesh::{
        skinning::{SkinnedMesh, SkinnedMeshInverseBindposes},
        GpuBufferInfo, Mesh, MeshVertexBufferLayout,
    },
    render_asset::RenderAssets,
    render_phase::{EntityRenderCommand, RenderCommandResult, TrackedRenderPass},
    render_resource::*,
    renderer::{AvailableTextureFormats, RenderDevice, RenderQueue},
    texture::{DefaultImageSampler, GpuImage, Image, ImageSampler, TextureFormatPixelInfo},
    view::{ComputedVisibility, ViewUniform, ViewUniformOffset, ViewUniforms},
    Extract, RenderApp, RenderStage,
};
use bevy_transform::components::GlobalTransform;
use std::num::NonZeroU64;

#[derive(Default)]
pub struct MeshRenderPlugin;

const MAX_JOINTS: usize = 256;
const JOINT_SIZE: usize = std::mem::size_of::<Mat4>();
pub(crate) const JOINT_BUFFER_SIZE: usize = MAX_JOINTS * JOINT_SIZE;

pub const MESH_VERTEX_OUTPUT: HandleUntyped =
    HandleUntyped::weak_from_u64(Shader::TYPE_UUID, 2645551199423808407);
pub const MESH_VIEW_TYPES_HANDLE: HandleUntyped =
    HandleUntyped::weak_from_u64(Shader::TYPE_UUID, 8140454348013264787);
pub const MESH_VIEW_BINDINGS_HANDLE: HandleUntyped =
    HandleUntyped::weak_from_u64(Shader::TYPE_UUID, 9076678235888822571);
pub const MESH_TYPES_HANDLE: HandleUntyped =
    HandleUntyped::weak_from_u64(Shader::TYPE_UUID, 2506024101911992377);
pub const MESH_BINDINGS_HANDLE: HandleUntyped =
    HandleUntyped::weak_from_u64(Shader::TYPE_UUID, 16831548636314682308);
pub const MESH_FUNCTIONS_HANDLE: HandleUntyped =
    HandleUntyped::weak_from_u64(Shader::TYPE_UUID, 6300874327833745635);
pub const MESH_SHADER_HANDLE: HandleUntyped =
    HandleUntyped::weak_from_u64(Shader::TYPE_UUID, 3252377289100772450);
pub const SKINNING_HANDLE: HandleUntyped =
    HandleUntyped::weak_from_u64(Shader::TYPE_UUID, 13215291596265391738);

impl Plugin for MeshRenderPlugin {
    fn build(&self, app: &mut bevy_app::App) {
        load_internal_asset!(
            app,
            MESH_VERTEX_OUTPUT,
            "mesh_vertex_output.wgsl",
            Shader::from_wgsl
        );
        load_internal_asset!(
            app,
            MESH_VIEW_TYPES_HANDLE,
            "mesh_view_types.wgsl",
            Shader::from_wgsl
        );
        load_internal_asset!(
            app,
            MESH_VIEW_BINDINGS_HANDLE,
            "mesh_view_bindings.wgsl",
            Shader::from_wgsl
        );
        load_internal_asset!(app, MESH_TYPES_HANDLE, "mesh_types.wgsl", Shader::from_wgsl);
        load_internal_asset!(
            app,
            MESH_BINDINGS_HANDLE,
            "mesh_bindings.wgsl",
            Shader::from_wgsl
        );
        load_internal_asset!(
            app,
            MESH_FUNCTIONS_HANDLE,
            "mesh_functions.wgsl",
            Shader::from_wgsl
        );
        load_internal_asset!(app, MESH_SHADER_HANDLE, "mesh.wgsl", Shader::from_wgsl);
        load_internal_asset!(app, SKINNING_HANDLE, "skinning.wgsl", Shader::from_wgsl);

        app.add_plugin(UniformComponentPlugin::<MeshUniform>::default());

        if let Ok(render_app) = app.get_sub_app_mut(RenderApp) {
            render_app
                .init_resource::<MeshPipeline>()
                .init_resource::<SkinnedMeshUniform>()
                .add_system_to_stage(RenderStage::Extract, extract_meshes)
                .add_system_to_stage(RenderStage::Extract, extract_skinned_meshes)
                .add_system_to_stage(RenderStage::Prepare, prepare_skinned_meshes)
                .add_system_to_stage(RenderStage::Queue, queue_mesh_bind_group)
                .add_system_to_stage(RenderStage::Queue, queue_mesh_view_bind_groups);
        }
    }
}

#[derive(Component, ShaderType, Clone)]
pub struct MeshUniform {
    pub transform: Mat4,
    pub inverse_transpose_model: Mat4,
    pub flags: u32,
}

// NOTE: These must match the bit flags in bevy_pbr2/src/render/mesh.wgsl!
bitflags::bitflags! {
    #[repr(transparent)]
    struct MeshFlags: u32 {
        const SHADOW_RECEIVER            = (1 << 0);
        const NONE                       = 0;
        const UNINITIALIZED              = 0xFFFF;
    }
}

pub fn extract_meshes(
    mut commands: Commands,
    mut prev_caster_commands_len: Local<usize>,
    mut prev_not_caster_commands_len: Local<usize>,
    meshes_query: Extract<
        Query<(
            Entity,
            &ComputedVisibility,
            &GlobalTransform,
            &Handle<Mesh>,
            Option<With<NotShadowReceiver>>,
            Option<With<NotShadowCaster>>,
        )>,
    >,
) {
    let mut caster_commands = Vec::with_capacity(*prev_caster_commands_len);
    let mut not_caster_commands = Vec::with_capacity(*prev_not_caster_commands_len);
    let visible_meshes = meshes_query.iter().filter(|(_, vis, ..)| vis.is_visible());

    for (entity, _, transform, handle, not_receiver, not_caster) in visible_meshes {
        let transform = transform.compute_matrix();
        let shadow_receiver_flags = if not_receiver.is_some() {
            MeshFlags::empty().bits
        } else {
            MeshFlags::SHADOW_RECEIVER.bits
        };
        let uniform = MeshUniform {
            flags: shadow_receiver_flags,
            transform,
            inverse_transpose_model: transform.inverse().transpose(),
        };
        if not_caster.is_some() {
            not_caster_commands.push((entity, (handle.clone_weak(), uniform, NotShadowCaster)));
        } else {
            caster_commands.push((entity, (handle.clone_weak(), uniform)));
        }
    }
    *prev_caster_commands_len = caster_commands.len();
    *prev_not_caster_commands_len = not_caster_commands.len();
    commands.insert_or_spawn_batch(caster_commands);
    commands.insert_or_spawn_batch(not_caster_commands);
}

#[derive(Debug, Default)]
pub struct ExtractedJoints {
    pub buffer: Vec<Mat4>,
}

#[derive(Component)]
pub struct SkinnedMeshJoints {
    pub index: u32,
}

impl SkinnedMeshJoints {
    #[inline]
    pub fn build(
        skin: &SkinnedMesh,
        inverse_bindposes: &Assets<SkinnedMeshInverseBindposes>,
        joints: &Query<&GlobalTransform>,
        buffer: &mut Vec<Mat4>,
    ) -> Option<Self> {
        let inverse_bindposes = inverse_bindposes.get(&skin.inverse_bindposes)?;
        let bindposes = inverse_bindposes.iter();
        let skin_joints = skin.joints.iter();
        let start = buffer.len();
        for (inverse_bindpose, joint) in bindposes.zip(skin_joints).take(MAX_JOINTS) {
            if let Ok(joint) = joints.get(*joint) {
                buffer.push(joint.affine() * *inverse_bindpose);
            } else {
                buffer.truncate(start);
                return None;
            }
        }

        // Pad to 256 byte alignment
        while buffer.len() % 4 != 0 {
            buffer.push(Mat4::ZERO);
        }
        Some(Self {
            index: start as u32,
        })
    }

    pub fn to_buffer_index(mut self) -> Self {
        self.index *= std::mem::size_of::<Mat4>() as u32;
        self
    }
}

pub fn extract_skinned_meshes(
    mut commands: Commands,
    mut previous_len: Local<usize>,
    mut previous_joint_len: Local<usize>,
    query: Extract<Query<(Entity, &ComputedVisibility, &SkinnedMesh)>>,
    inverse_bindposes: Extract<Res<Assets<SkinnedMeshInverseBindposes>>>,
    joint_query: Extract<Query<&GlobalTransform>>,
) {
    let mut values = Vec::with_capacity(*previous_len);
    let mut joints = Vec::with_capacity(*previous_joint_len);
    let mut last_start = 0;

    for (entity, computed_visibility, skin) in query.iter() {
        if !computed_visibility.is_visible() {
            continue;
        }
        // PERF: This can be expensive, can we move this to prepare?
        if let Some(skinned_joints) =
            SkinnedMeshJoints::build(skin, &inverse_bindposes, &joint_query, &mut joints)
        {
            last_start = last_start.max(skinned_joints.index as usize);
            values.push((entity, (skinned_joints.to_buffer_index(),)));
        }
    }

    // Pad out the buffer to ensure that there's enough space for bindings
    while joints.len() - last_start < MAX_JOINTS {
        joints.push(Mat4::ZERO);
    }

    *previous_len = values.len();
    *previous_joint_len = joints.len();
    commands.insert_resource(ExtractedJoints { buffer: joints });
    commands.insert_or_spawn_batch(values);
}

#[derive(Clone)]
pub struct MeshPipeline {
    pub view_layout: BindGroupLayout,
    pub mesh_layout: BindGroupLayout,
    pub skinned_mesh_layout: BindGroupLayout,
    // This dummy white texture is to be used in place of optional StandardMaterial textures
    pub dummy_white_gpu_image: GpuImage,
    pub clustered_forward_buffer_binding_type: BufferBindingType,
}

impl FromWorld for MeshPipeline {
    fn from_world(world: &mut World) -> Self {
        let mut system_state: SystemState<(
            Res<RenderDevice>,
            Res<DefaultImageSampler>,
            Res<RenderQueue>,
            Res<AvailableTextureFormats>,
        )> = SystemState::new(world);
        let (render_device, default_sampler, render_queue, available_texture_formats) =
            system_state.get_mut(world);
        let clustered_forward_buffer_binding_type = render_device
            .get_supported_read_only_binding_type(CLUSTERED_FORWARD_STORAGE_BUFFER_COUNT);

        let view_layout = render_device.create_bind_group_layout(&BindGroupLayoutDescriptor {
            entries: &[
                // View
                BindGroupLayoutEntry {
                    binding: 0,
                    visibility: ShaderStages::VERTEX | ShaderStages::FRAGMENT,
                    ty: BindingType::Buffer {
                        ty: BufferBindingType::Uniform,
                        has_dynamic_offset: true,
                        min_binding_size: Some(ViewUniform::min_size()),
                    },
                    count: None,
                },
                // Lights
                BindGroupLayoutEntry {
                    binding: 1,
                    visibility: ShaderStages::FRAGMENT,
                    ty: BindingType::Buffer {
                        ty: BufferBindingType::Uniform,
                        has_dynamic_offset: true,
                        min_binding_size: Some(GpuLights::min_size()),
                    },
                    count: None,
                },
                // Point Shadow Texture Cube Array
                BindGroupLayoutEntry {
                    binding: 2,
                    visibility: ShaderStages::FRAGMENT,
                    ty: BindingType::Texture {
                        multisampled: false,
                        sample_type: TextureSampleType::Depth,
                        #[cfg(not(feature = "webgl"))]
                        view_dimension: TextureViewDimension::CubeArray,
                        #[cfg(feature = "webgl")]
                        view_dimension: TextureViewDimension::Cube,
                    },
                    count: None,
                },
                // Point Shadow Texture Array Sampler
                BindGroupLayoutEntry {
                    binding: 3,
                    visibility: ShaderStages::FRAGMENT,
                    ty: BindingType::Sampler(SamplerBindingType::Comparison),
                    count: None,
                },
                // Directional Shadow Texture Array
                BindGroupLayoutEntry {
                    binding: 4,
                    visibility: ShaderStages::FRAGMENT,
                    ty: BindingType::Texture {
                        multisampled: false,
                        sample_type: TextureSampleType::Depth,
                        #[cfg(not(feature = "webgl"))]
                        view_dimension: TextureViewDimension::D2Array,
                        #[cfg(feature = "webgl")]
                        view_dimension: TextureViewDimension::D2,
                    },
                    count: None,
                },
                // Directional Shadow Texture Array Sampler
                BindGroupLayoutEntry {
                    binding: 5,
                    visibility: ShaderStages::FRAGMENT,
                    ty: BindingType::Sampler(SamplerBindingType::Comparison),
                    count: None,
                },
                // PointLights
                BindGroupLayoutEntry {
                    binding: 6,
                    visibility: ShaderStages::FRAGMENT,
                    ty: BindingType::Buffer {
                        ty: clustered_forward_buffer_binding_type,
                        has_dynamic_offset: false,
                        min_binding_size: Some(GpuPointLights::min_size(
                            clustered_forward_buffer_binding_type,
                        )),
                    },
                    count: None,
                },
                // ClusteredLightIndexLists
                BindGroupLayoutEntry {
                    binding: 7,
                    visibility: ShaderStages::FRAGMENT,
                    ty: BindingType::Buffer {
                        ty: clustered_forward_buffer_binding_type,
                        has_dynamic_offset: false,
                        min_binding_size: Some(
                            ViewClusterBindings::min_size_cluster_light_index_lists(
                                clustered_forward_buffer_binding_type,
                            ),
                        ),
                    },
                    count: None,
                },
                // ClusterOffsetsAndCounts
                BindGroupLayoutEntry {
                    binding: 8,
                    visibility: ShaderStages::FRAGMENT,
                    ty: BindingType::Buffer {
                        ty: clustered_forward_buffer_binding_type,
                        has_dynamic_offset: false,
                        min_binding_size: Some(
                            ViewClusterBindings::min_size_cluster_offsets_and_counts(
                                clustered_forward_buffer_binding_type,
                            ),
                        ),
                    },
                    count: None,
                },
            ],
            label: Some("mesh_view_layout"),
        });

        let mesh_binding = BindGroupLayoutEntry {
            binding: 0,
            visibility: ShaderStages::VERTEX | ShaderStages::FRAGMENT,
            ty: BindingType::Buffer {
                ty: BufferBindingType::Uniform,
                has_dynamic_offset: true,
                min_binding_size: Some(MeshUniform::min_size()),
            },
            count: None,
        };

        let mesh_layout = render_device.create_bind_group_layout(&BindGroupLayoutDescriptor {
            entries: &[mesh_binding],
            label: Some("mesh_layout"),
        });

        let skinned_mesh_layout =
            render_device.create_bind_group_layout(&BindGroupLayoutDescriptor {
                entries: &[
                    mesh_binding,
                    BindGroupLayoutEntry {
                        binding: 1,
                        visibility: ShaderStages::VERTEX,
                        ty: BindingType::Buffer {
                            ty: BufferBindingType::Uniform,
                            has_dynamic_offset: true,
                            min_binding_size: BufferSize::new(JOINT_BUFFER_SIZE as u64),
                        },
                        count: None,
                    },
                ],
                label: Some("skinned_mesh_layout"),
            });

        // A 1x1x1 'all 1.0' texture to use as a dummy texture to use in place of optional StandardMaterial textures
        let dummy_white_gpu_image = {
            let image = Image::new_fill(
                Extent3d::default(),
                TextureDimension::D2,
                &[255u8; 4],
                available_texture_formats[0],
            );
            let texture = render_device.create_texture(&image.texture_descriptor);
            let sampler = match image.sampler_descriptor {
                ImageSampler::Default => (**default_sampler).clone(),
                ImageSampler::Descriptor(descriptor) => render_device.create_sampler(&descriptor),
            };

            let format_size = image.texture_descriptor.format.pixel_size();
            render_queue.write_texture(
                ImageCopyTexture {
                    texture: &texture,
                    mip_level: 0,
                    origin: Origin3d::ZERO,
                    aspect: TextureAspect::All,
                },
                &image.data,
                ImageDataLayout {
                    offset: 0,
                    bytes_per_row: Some(
                        std::num::NonZeroU32::new(
                            image.texture_descriptor.size.width * format_size as u32,
                        )
                        .unwrap(),
                    ),
                    rows_per_image: None,
                },
                image.texture_descriptor.size,
            );

            let texture_view = texture.create_view(&TextureViewDescriptor::default());
            GpuImage {
                texture,
                texture_view,
                texture_format: image.texture_descriptor.format,
                sampler,
                size: Vec2::new(
                    image.texture_descriptor.size.width as f32,
                    image.texture_descriptor.size.height as f32,
                ),
            }
        };
        MeshPipeline {
            view_layout,
            mesh_layout,
            skinned_mesh_layout,
            clustered_forward_buffer_binding_type,
            dummy_white_gpu_image,
        }
    }
}

impl MeshPipeline {
    pub fn get_image_texture<'a>(
        &'a self,
        gpu_images: &'a RenderAssets<Image>,
        handle_option: &Option<Handle<Image>>,
    ) -> Option<(&'a TextureView, &'a Sampler)> {
        if let Some(handle) = handle_option {
            let gpu_image = gpu_images.get(handle)?;
            Some((&gpu_image.texture_view, &gpu_image.sampler))
        } else {
            Some((
                &self.dummy_white_gpu_image.texture_view,
                &self.dummy_white_gpu_image.sampler,
            ))
        }
    }
}

bitflags::bitflags! {
    #[repr(transparent)]
    // NOTE: Apparently quadro drivers support up to 64x MSAA.
    /// MSAA uses the highest 6 bits for the MSAA sample count - 1 to support up to 64x MSAA.
    pub struct MeshPipelineKey: u32 {
        const NONE                        = 0;
        const TRANSPARENT_MAIN_PASS       = (1 << 0);
        const MSAA_RESERVED_BITS          = MeshPipelineKey::MSAA_MASK_BITS << MeshPipelineKey::MSAA_SHIFT_BITS;
        const PRIMITIVE_TOPOLOGY_RESERVED_BITS = MeshPipelineKey::PRIMITIVE_TOPOLOGY_MASK_BITS << MeshPipelineKey::PRIMITIVE_TOPOLOGY_SHIFT_BITS;
    }
}

impl MeshPipelineKey {
    const MSAA_MASK_BITS: u32 = 0b111111;
    const MSAA_SHIFT_BITS: u32 = 32 - 6;
    const PRIMITIVE_TOPOLOGY_MASK_BITS: u32 = 0b111;
    const PRIMITIVE_TOPOLOGY_SHIFT_BITS: u32 = Self::MSAA_SHIFT_BITS - 3;

    pub fn from_msaa_samples(msaa_samples: u32) -> Self {
        let msaa_bits = ((msaa_samples - 1) & Self::MSAA_MASK_BITS) << Self::MSAA_SHIFT_BITS;
        MeshPipelineKey::from_bits(msaa_bits).unwrap()
    }

    pub fn msaa_samples(&self) -> u32 {
        ((self.bits >> Self::MSAA_SHIFT_BITS) & Self::MSAA_MASK_BITS) + 1
    }

    pub fn from_primitive_topology(primitive_topology: PrimitiveTopology) -> Self {
        let primitive_topology_bits = ((primitive_topology as u32)
            & Self::PRIMITIVE_TOPOLOGY_MASK_BITS)
            << Self::PRIMITIVE_TOPOLOGY_SHIFT_BITS;
        MeshPipelineKey::from_bits(primitive_topology_bits).unwrap()
    }

    pub fn primitive_topology(&self) -> PrimitiveTopology {
        let primitive_topology_bits =
            (self.bits >> Self::PRIMITIVE_TOPOLOGY_SHIFT_BITS) & Self::PRIMITIVE_TOPOLOGY_MASK_BITS;
        match primitive_topology_bits {
            x if x == PrimitiveTopology::PointList as u32 => PrimitiveTopology::PointList,
            x if x == PrimitiveTopology::LineList as u32 => PrimitiveTopology::LineList,
            x if x == PrimitiveTopology::LineStrip as u32 => PrimitiveTopology::LineStrip,
            x if x == PrimitiveTopology::TriangleList as u32 => PrimitiveTopology::TriangleList,
            x if x == PrimitiveTopology::TriangleStrip as u32 => PrimitiveTopology::TriangleStrip,
            _ => PrimitiveTopology::default(),
        }
    }
}

impl SpecializedMeshPipeline for MeshPipeline {
    type Key = MeshPipelineKey;

    fn specialize(
        &self,
        key: Self::Key,
        layout: &MeshVertexBufferLayout,
    ) -> Result<RenderPipelineDescriptor, SpecializedMeshPipelineError> {
        let mut vertex_attributes = vec![
            Mesh::ATTRIBUTE_POSITION.at_shader_location(0),
            Mesh::ATTRIBUTE_NORMAL.at_shader_location(1),
        ];

        let mut shader_defs = Vec::new();
        if layout.contains(Mesh::ATTRIBUTE_UV_0) {
            shader_defs.push(String::from("VERTEX_UVS"));
            vertex_attributes.push(Mesh::ATTRIBUTE_UV_0.at_shader_location(2));
        }

        if layout.contains(Mesh::ATTRIBUTE_TANGENT) {
            shader_defs.push(String::from("VERTEX_TANGENTS"));
            vertex_attributes.push(Mesh::ATTRIBUTE_TANGENT.at_shader_location(3));
        }

        if layout.contains(Mesh::ATTRIBUTE_COLOR) {
            shader_defs.push(String::from("VERTEX_COLORS"));
            vertex_attributes.push(Mesh::ATTRIBUTE_COLOR.at_shader_location(4));
        }

        let mut bind_group_layout = vec![self.view_layout.clone()];
        if layout.contains(Mesh::ATTRIBUTE_JOINT_INDEX)
            && layout.contains(Mesh::ATTRIBUTE_JOINT_WEIGHT)
        {
            shader_defs.push(String::from("SKINNED"));
            vertex_attributes.push(Mesh::ATTRIBUTE_JOINT_INDEX.at_shader_location(5));
            vertex_attributes.push(Mesh::ATTRIBUTE_JOINT_WEIGHT.at_shader_location(6));
            bind_group_layout.push(self.skinned_mesh_layout.clone());
        } else {
            bind_group_layout.push(self.mesh_layout.clone());
        };

        let vertex_buffer_layout = layout.get_layout(&vertex_attributes)?;

        let (label, blend, depth_write_enabled);
        if key.contains(MeshPipelineKey::TRANSPARENT_MAIN_PASS) {
            label = "transparent_mesh_pipeline".into();
            blend = Some(BlendState::ALPHA_BLENDING);
            // For the transparent pass, fragments that are closer will be alpha blended
            // but their depth is not written to the depth buffer
            depth_write_enabled = false;
        } else {
            label = "opaque_mesh_pipeline".into();
            blend = Some(BlendState::REPLACE);
            // For the opaque and alpha mask passes, fragments that are closer will replace
            // the current fragment value in the output and the depth is written to the
            // depth buffer
            depth_write_enabled = true;
        }

        Ok(RenderPipelineDescriptor {
            vertex: VertexState {
                shader: MESH_SHADER_HANDLE.typed::<Shader>(),
                entry_point: "vertex".into(),
                shader_defs: shader_defs.clone(),
                buffers: vec![vertex_buffer_layout],
            },
            fragment: Some(FragmentState {
                shader: MESH_SHADER_HANDLE.typed::<Shader>(),
                shader_defs,
                entry_point: "fragment".into(),
                targets: vec![Some(ColorTargetState {
                    format: self.dummy_white_gpu_image.texture_format,
                    blend,
                    write_mask: ColorWrites::ALL,
                })],
            }),
            layout: Some(bind_group_layout),
            primitive: PrimitiveState {
                front_face: FrontFace::Ccw,
                cull_mode: Some(Face::Back),
                unclipped_depth: false,
                polygon_mode: PolygonMode::Fill,
                conservative: false,
                topology: key.primitive_topology(),
                strip_index_format: None,
            },
            depth_stencil: Some(DepthStencilState {
                format: TextureFormat::Depth32Float,
                depth_write_enabled,
                depth_compare: CompareFunction::Greater,
                stencil: StencilState {
                    front: StencilFaceState::IGNORE,
                    back: StencilFaceState::IGNORE,
                    read_mask: 0,
                    write_mask: 0,
                },
                bias: DepthBiasState {
                    constant: 0,
                    slope_scale: 0.0,
                    clamp: 0.0,
                },
            }),
            multisample: MultisampleState {
                count: key.msaa_samples(),
                mask: !0,
                alpha_to_coverage_enabled: false,
            },
            label: Some(label),
        })
    }
}

pub struct MeshBindGroup {
    pub normal: BindGroup,
    pub skinned: Option<BindGroup>,
}

pub fn queue_mesh_bind_group(
    mut commands: Commands,
    mesh_pipeline: Res<MeshPipeline>,
    render_device: Res<RenderDevice>,
    mesh_uniforms: Res<ComponentUniforms<MeshUniform>>,
    skinned_mesh_uniform: Res<SkinnedMeshUniform>,
) {
    if let Some(mesh_binding) = mesh_uniforms.uniforms().binding() {
        let mut mesh_bind_group = MeshBindGroup {
            normal: render_device.create_bind_group(&BindGroupDescriptor {
                entries: &[BindGroupEntry {
                    binding: 0,
                    resource: mesh_binding.clone(),
                }],
                label: Some("mesh_bind_group"),
                layout: &mesh_pipeline.mesh_layout,
            }),
            skinned: None,
        };

        if let Some(skinned_joints_buffer) = skinned_mesh_uniform.buffer.buffer() {
            mesh_bind_group.skinned = Some(render_device.create_bind_group(&BindGroupDescriptor {
                entries: &[
                    BindGroupEntry {
                        binding: 0,
                        resource: mesh_binding,
                    },
                    BindGroupEntry {
                        binding: 1,
                        resource: BindingResource::Buffer(BufferBinding {
                            buffer: skinned_joints_buffer,
                            offset: 0,
                            size: Some(NonZeroU64::new(JOINT_BUFFER_SIZE as u64).unwrap()),
                        }),
                    },
                ],
                label: Some("skinned_mesh_bind_group"),
                layout: &mesh_pipeline.skinned_mesh_layout,
            }));
        }
        commands.insert_resource(mesh_bind_group);
    }
}

// NOTE: This is using BufferVec because it is using a trick to allow a fixed-size array
// in a uniform buffer to be used like a variable-sized array by only writing the valid data
// into the buffer, knowing the number of valid items starting from the dynamic offset, and
// ignoring the rest, whether they're valid for other dynamic offsets or not. This trick may
// be supported later in encase, and then we should make use of it.

pub struct SkinnedMeshUniform {
    pub buffer: BufferVec<Mat4>,
}

impl Default for SkinnedMeshUniform {
    fn default() -> Self {
        Self {
            buffer: BufferVec::new(BufferUsages::UNIFORM),
        }
    }
}

pub fn prepare_skinned_meshes(
    render_device: Res<RenderDevice>,
    render_queue: Res<RenderQueue>,
    extracted_joints: Res<ExtractedJoints>,
    mut skinned_mesh_uniform: ResMut<SkinnedMeshUniform>,
) {
    if extracted_joints.buffer.is_empty() {
        return;
    }

    skinned_mesh_uniform.buffer.clear();
    skinned_mesh_uniform
        .buffer
        .reserve(extracted_joints.buffer.len(), &render_device);
    for joint in &extracted_joints.buffer {
        skinned_mesh_uniform.buffer.push(*joint);
    }
    skinned_mesh_uniform
        .buffer
        .write_buffer(&render_device, &render_queue);
}

#[derive(Component)]
pub struct MeshViewBindGroup {
    pub value: BindGroup,
}

#[allow(clippy::too_many_arguments)]
pub fn queue_mesh_view_bind_groups(
    mut commands: Commands,
    render_device: Res<RenderDevice>,
    mesh_pipeline: Res<MeshPipeline>,
    shadow_pipeline: Res<ShadowPipeline>,
    light_meta: Res<LightMeta>,
    global_light_meta: Res<GlobalLightMeta>,
    view_uniforms: Res<ViewUniforms>,
    views: Query<(Entity, &ViewShadowBindings, &ViewClusterBindings)>,
) {
    if let (Some(view_binding), Some(light_binding), Some(point_light_binding)) = (
        view_uniforms.uniforms.binding(),
        light_meta.view_gpu_lights.binding(),
        global_light_meta.gpu_point_lights.binding(),
    ) {
        for (entity, view_shadow_bindings, view_cluster_bindings) in &views {
            let view_bind_group = render_device.create_bind_group(&BindGroupDescriptor {
                entries: &[
                    BindGroupEntry {
                        binding: 0,
                        resource: view_binding.clone(),
                    },
                    BindGroupEntry {
                        binding: 1,
                        resource: light_binding.clone(),
                    },
                    BindGroupEntry {
                        binding: 2,
                        resource: BindingResource::TextureView(
                            &view_shadow_bindings.point_light_depth_texture_view,
                        ),
                    },
                    BindGroupEntry {
                        binding: 3,
                        resource: BindingResource::Sampler(&shadow_pipeline.point_light_sampler),
                    },
                    BindGroupEntry {
                        binding: 4,
                        resource: BindingResource::TextureView(
                            &view_shadow_bindings.directional_light_depth_texture_view,
                        ),
                    },
                    BindGroupEntry {
                        binding: 5,
                        resource: BindingResource::Sampler(
                            &shadow_pipeline.directional_light_sampler,
                        ),
                    },
                    BindGroupEntry {
                        binding: 6,
                        resource: point_light_binding.clone(),
                    },
                    BindGroupEntry {
                        binding: 7,
                        resource: view_cluster_bindings.light_index_lists_binding().unwrap(),
                    },
                    BindGroupEntry {
                        binding: 8,
                        resource: view_cluster_bindings.offsets_and_counts_binding().unwrap(),
                    },
                ],
                label: Some("mesh_view_bind_group"),
                layout: &mesh_pipeline.view_layout,
            });

            commands.entity(entity).insert(MeshViewBindGroup {
                value: view_bind_group,
            });
        }
    }
}

pub struct SetMeshViewBindGroup<const I: usize>;
impl<const I: usize> EntityRenderCommand for SetMeshViewBindGroup<I> {
    type Param = SQuery<(
        Read<ViewUniformOffset>,
        Read<ViewLightsUniformOffset>,
        Read<MeshViewBindGroup>,
    )>;
    #[inline]
    fn render<'w>(
        view: Entity,
        _item: Entity,
        view_query: SystemParamItem<'w, '_, Self::Param>,
        pass: &mut TrackedRenderPass<'w>,
    ) -> RenderCommandResult {
        let (view_uniform, view_lights, mesh_view_bind_group) = view_query.get_inner(view).unwrap();
        pass.set_bind_group(
            I,
            &mesh_view_bind_group.value,
            &[view_uniform.offset, view_lights.offset],
        );

        RenderCommandResult::Success
    }
}

pub struct SetMeshBindGroup<const I: usize>;
impl<const I: usize> EntityRenderCommand for SetMeshBindGroup<I> {
    type Param = (
        SRes<MeshBindGroup>,
        SQuery<(
            Read<DynamicUniformIndex<MeshUniform>>,
            Option<Read<SkinnedMeshJoints>>,
        )>,
    );
    #[inline]
    fn render<'w>(
        _view: Entity,
        item: Entity,
        (mesh_bind_group, mesh_query): SystemParamItem<'w, '_, Self::Param>,
        pass: &mut TrackedRenderPass<'w>,
    ) -> RenderCommandResult {
        let (mesh_index, skinned_mesh_joints) = mesh_query.get(item).unwrap();
        if let Some(joints) = skinned_mesh_joints {
            pass.set_bind_group(
                I,
                mesh_bind_group.into_inner().skinned.as_ref().unwrap(),
                &[mesh_index.index(), joints.index],
            );
        } else {
            pass.set_bind_group(
                I,
                &mesh_bind_group.into_inner().normal,
                &[mesh_index.index()],
            );
        }
        RenderCommandResult::Success
    }
}

pub struct DrawMesh;
impl EntityRenderCommand for DrawMesh {
    type Param = (SRes<RenderAssets<Mesh>>, SQuery<Read<Handle<Mesh>>>);
    #[inline]
    fn render<'w>(
        _view: Entity,
        item: Entity,
        (meshes, mesh_query): SystemParamItem<'w, '_, Self::Param>,
        pass: &mut TrackedRenderPass<'w>,
    ) -> RenderCommandResult {
        let mesh_handle = mesh_query.get(item).unwrap();
        if let Some(gpu_mesh) = meshes.into_inner().get(mesh_handle) {
            pass.set_vertex_buffer(0, gpu_mesh.vertex_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..1);
                }
                GpuBufferInfo::NonIndexed { vertex_count } => {
                    pass.draw(0..*vertex_count, 0..1);
                }
            }
            RenderCommandResult::Success
        } else {
            RenderCommandResult::Failure
        }
    }
}

#[cfg(test)]
mod tests {
    use super::MeshPipelineKey;
    #[test]
    fn mesh_key_msaa_samples() {
        for i in 1..=64 {
            assert_eq!(MeshPipelineKey::from_msaa_samples(i).msaa_samples(), i);
        }
    }
}