bevy/crates/bevy_pbr/src/render/mesh.rs

use crate::{
    GlobalLightMeta, GpuLights, GpuPointLights, LightMeta, NotShadowCaster, NotShadowReceiver,
    ShadowPipeline, ViewClusterBindings, ViewLightsUniformOffset, ViewShadowBindings,
    CLUSTERED_FORWARD_STORAGE_BUFFER_COUNT, MAX_DIRECTIONAL_LIGHTS,
};
use bevy_app::Plugin;
use bevy_asset::{load_internal_asset, Assets, Handle, HandleUntyped};
use bevy_core_pipeline::prepass::ViewPrepassTextures;
use bevy_ecs::{
    prelude::*,
    query::ROQueryItem,
    system::{lifetimeless::*, SystemParamItem, SystemState},
};
use bevy_math::{Mat3A, Mat4, Vec2};
use bevy_reflect::TypeUuid;
use bevy_render::{
    extract_component::{ComponentUniforms, DynamicUniformIndex, UniformComponentPlugin},
    globals::{GlobalsBuffer, GlobalsUniform},
    mesh::{
        skinning::{SkinnedMesh, SkinnedMeshInverseBindposes},
        GpuBufferInfo, Mesh, MeshVertexBufferLayout,
    },
    prelude::Msaa,
    render_asset::RenderAssets,
    render_phase::{PhaseItem, RenderCommand, RenderCommandResult, TrackedRenderPass},
    render_resource::*,
    renderer::{RenderDevice, RenderQueue},
    texture::{
        BevyDefault, DefaultImageSampler, FallbackImagesDepth, FallbackImagesMsaa, GpuImage, Image,
        ImageSampler, TextureFormatPixelInfo,
    },
    view::{ComputedVisibility, ViewTarget, 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_pbr/src/render/mesh_types.wgsl!
bitflags::bitflags! {
    #[repr(transparent)]
    struct MeshFlags: u32 {
        const SHADOW_RECEIVER            = (1 << 0);
        // Indicates the sign of the determinant of the 3x3 model matrix. If the sign is positive,
        // then the flag should be set, else it should not be set.
        const SIGN_DETERMINANT_MODEL_3X3 = (1 << 31);
        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 mut flags = if not_receiver.is_some() {
            MeshFlags::empty()
        } else {
            MeshFlags::SHADOW_RECEIVER
        };
        if Mat3A::from_mat4(transform).determinant().is_sign_positive() {
            flags |= MeshFlags::SIGN_DETERMINANT_MODEL_3X3;
        }
        let uniform = MeshUniform {
            flags: flags.bits,
            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(Component)]
pub struct SkinnedMeshJoints {
    pub index: u32,
}

impl SkinnedMeshJoints {
    #[inline]
    pub fn build(
        skin: &SkinnedMesh,
        inverse_bindposes: &Assets<SkinnedMeshInverseBindposes>,
        joints: &Query<&GlobalTransform>,
        buffer: &mut BufferVec<Mat4>,
    ) -> Option<Self> {
        let inverse_bindposes = inverse_bindposes.get(&skin.inverse_bindposes)?;
        let start = buffer.len();
        let target = start + skin.joints.len().min(MAX_JOINTS);
        buffer.extend(
            joints
                .iter_many(&skin.joints)
                .zip(inverse_bindposes.iter())
                .map(|(joint, bindpose)| joint.affine() * *bindpose),
        );
        // iter_many will skip any failed fetches. This will cause it to assign the wrong bones,
        // so just bail by truncating to the start.
        if buffer.len() != target {
            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 uniform: ResMut<SkinnedMeshUniform>,
    query: Extract<Query<(Entity, &ComputedVisibility, &SkinnedMesh)>>,
    inverse_bindposes: Extract<Res<Assets<SkinnedMeshInverseBindposes>>>,
    joint_query: Extract<Query<&GlobalTransform>>,
) {
    uniform.buffer.clear();
    let mut values = Vec::with_capacity(*previous_len);
    let mut last_start = 0;

    for (entity, computed_visibility, skin) in &query {
        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 uniform.buffer)
        {
            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 uniform.buffer.len() - last_start < MAX_JOINTS {
        uniform.buffer.push(Mat4::ZERO);
    }

    *previous_len = values.len();
    commands.insert_or_spawn_batch(values);
}

#[derive(Resource, Clone)]
pub struct MeshPipeline {
    pub view_layout: BindGroupLayout,
    pub view_layout_multisampled: 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>,
        )> = SystemState::new(world);
        let (render_device, default_sampler, render_queue) = system_state.get_mut(world);
        let clustered_forward_buffer_binding_type = render_device
            .get_supported_read_only_binding_type(CLUSTERED_FORWARD_STORAGE_BUFFER_COUNT);

        /// Returns the appropriate bind group layout vec based on the parameters
        fn layout_entries(
            clustered_forward_buffer_binding_type: BufferBindingType,
            multisampled: bool,
        ) -> Vec<BindGroupLayoutEntry> {
            let mut entries = vec![
                // 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,
                },
                // Globals
                BindGroupLayoutEntry {
                    binding: 9,
                    visibility: ShaderStages::VERTEX_FRAGMENT,
                    ty: BindingType::Buffer {
                        ty: BufferBindingType::Uniform,
                        has_dynamic_offset: false,
                        min_binding_size: Some(GlobalsUniform::min_size()),
                    },
                    count: None,
                },
            ];
            if cfg!(not(feature = "webgl")) {
                // Depth texture
                entries.push(BindGroupLayoutEntry {
                    binding: 10,
                    visibility: ShaderStages::FRAGMENT,
                    ty: BindingType::Texture {
                        multisampled,
                        sample_type: TextureSampleType::Depth,
                        view_dimension: TextureViewDimension::D2,
                    },
                    count: None,
                });
                // Normal texture
                entries.push(BindGroupLayoutEntry {
                    binding: 11,
                    visibility: ShaderStages::FRAGMENT,
                    ty: BindingType::Texture {
                        multisampled,
                        sample_type: TextureSampleType::Float { filterable: true },
                        view_dimension: TextureViewDimension::D2,
                    },
                    count: None,
                });
            }
            entries
        }

        let view_layout = render_device.create_bind_group_layout(&BindGroupLayoutDescriptor {
            label: Some("mesh_view_layout"),
            entries: &layout_entries(clustered_forward_buffer_binding_type, false),
        });

        let view_layout_multisampled =
            render_device.create_bind_group_layout(&BindGroupLayoutDescriptor {
                label: Some("mesh_view_layout_multisampled"),
                entries: &layout_entries(clustered_forward_buffer_binding_type, true),
            });

        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],
                TextureFormat::bevy_default(),
            );
            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,
            view_layout_multisampled,
            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 3 bits for the MSAA log2(sample count) to support up to 128x MSAA.
    pub struct MeshPipelineKey: u32 {
        const NONE                        = 0;
        const TRANSPARENT_MAIN_PASS       = (1 << 0);
        const HDR                         = (1 << 1);
        const TONEMAP_IN_SHADER           = (1 << 2);
        const DEBAND_DITHER               = (1 << 3);
        const DEPTH_PREPASS               = (1 << 4);
        const NORMAL_PREPASS              = (1 << 5);
        const ALPHA_MASK                  = (1 << 6);
        const MSAA_RESERVED_BITS          = Self::MSAA_MASK_BITS << Self::MSAA_SHIFT_BITS;
        const PRIMITIVE_TOPOLOGY_RESERVED_BITS = Self::PRIMITIVE_TOPOLOGY_MASK_BITS << Self::PRIMITIVE_TOPOLOGY_SHIFT_BITS;
    }
}

impl MeshPipelineKey {
    const MSAA_MASK_BITS: u32 = 0b111;
    const MSAA_SHIFT_BITS: u32 = 32 - Self::MSAA_MASK_BITS.count_ones();
    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.trailing_zeros() & Self::MSAA_MASK_BITS) << Self::MSAA_SHIFT_BITS;
        Self::from_bits(msaa_bits).unwrap()
    }

    pub fn from_hdr(hdr: bool) -> Self {
        if hdr {
            MeshPipelineKey::HDR
        } else {
            MeshPipelineKey::NONE
        }
    }

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

    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;
        Self::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 shader_defs = Vec::new();
        let mut vertex_attributes = Vec::new();

        if layout.contains(Mesh::ATTRIBUTE_POSITION) {
            shader_defs.push("VERTEX_POSITIONS".into());
            vertex_attributes.push(Mesh::ATTRIBUTE_POSITION.at_shader_location(0));
        }

        if layout.contains(Mesh::ATTRIBUTE_NORMAL) {
            shader_defs.push("VERTEX_NORMALS".into());
            vertex_attributes.push(Mesh::ATTRIBUTE_NORMAL.at_shader_location(1));
        }

        shader_defs.push(ShaderDefVal::UInt(
            "MAX_DIRECTIONAL_LIGHTS".to_string(),
            MAX_DIRECTIONAL_LIGHTS as u32,
        ));

        if layout.contains(Mesh::ATTRIBUTE_UV_0) {
            shader_defs.push("VERTEX_UVS".into());
            vertex_attributes.push(Mesh::ATTRIBUTE_UV_0.at_shader_location(2));
        }

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

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

        let mut bind_group_layout = match key.msaa_samples() {
            1 => vec![self.view_layout.clone()],
            _ => {
                shader_defs.push("MULTISAMPLED".into());
                vec![self.view_layout_multisampled.clone()]
            }
        };

        if layout.contains(Mesh::ATTRIBUTE_JOINT_INDEX)
            && layout.contains(Mesh::ATTRIBUTE_JOINT_WEIGHT)
        {
            shader_defs.push("SKINNED".into());
            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;
        }

        if key.contains(MeshPipelineKey::TONEMAP_IN_SHADER) {
            shader_defs.push("TONEMAP_IN_SHADER".into());

            // Debanding is tied to tonemapping in the shader, cannot run without it.
            if key.contains(MeshPipelineKey::DEBAND_DITHER) {
                shader_defs.push("DEBAND_DITHER".into());
            }
        }

        let format = if key.contains(MeshPipelineKey::HDR) {
            ViewTarget::TEXTURE_FORMAT_HDR
        } else {
            TextureFormat::bevy_default()
        };

        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,
                    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::GreaterEqual,
                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),
        })
    }
}

#[derive(Resource)]
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.

#[derive(Resource)]
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>,
    mut skinned_mesh_uniform: ResMut<SkinnedMeshUniform>,
) {
    if skinned_mesh_uniform.buffer.is_empty() {
        return;
    }

    let len = skinned_mesh_uniform.buffer.len();
    skinned_mesh_uniform.buffer.reserve(len, &render_device);
    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,
        Option<&ViewPrepassTextures>,
    )>,
    mut fallback_images: FallbackImagesMsaa,
    mut fallback_depths: FallbackImagesDepth,
    msaa: Res<Msaa>,
    globals_buffer: Res<GlobalsBuffer>,
) {
    if let (Some(view_binding), Some(light_binding), Some(point_light_binding), Some(globals)) = (
        view_uniforms.uniforms.binding(),
        light_meta.view_gpu_lights.binding(),
        global_light_meta.gpu_point_lights.binding(),
        globals_buffer.buffer.binding(),
    ) {
        for (entity, view_shadow_bindings, view_cluster_bindings, prepass_textures) in &views {
            let layout = if msaa.samples > 1 {
                &mesh_pipeline.view_layout_multisampled
            } else {
                &mesh_pipeline.view_layout
            };

            let mut entries = vec![
                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(),
                },
                BindGroupEntry {
                    binding: 9,
                    resource: globals.clone(),
                },
            ];

            // When using WebGL with MSAA, we can't create the fallback textures required by the prepass
            // When using WebGL, and MSAA is disabled, we can't bind the textures either
            if cfg!(not(feature = "webgl")) {
                let depth_view = match prepass_textures.and_then(|x| x.depth.as_ref()) {
                    Some(texture) => &texture.default_view,
                    None => {
                        &fallback_depths
                            .image_for_samplecount(msaa.samples)
                            .texture_view
                    }
                };
                entries.push(BindGroupEntry {
                    binding: 10,
                    resource: BindingResource::TextureView(depth_view),
                });

                let normal_view = match prepass_textures.and_then(|x| x.normal.as_ref()) {
                    Some(texture) => &texture.default_view,
                    None => {
                        &fallback_images
                            .image_for_samplecount(msaa.samples)
                            .texture_view
                    }
                };
                entries.push(BindGroupEntry {
                    binding: 11,
                    resource: BindingResource::TextureView(normal_view),
                });
            }

            let view_bind_group = render_device.create_bind_group(&BindGroupDescriptor {
                entries: &entries,
                label: Some("mesh_view_bind_group"),
                layout,
            });

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

pub struct SetMeshViewBindGroup<const I: usize>;
impl<P: PhaseItem, const I: usize> RenderCommand<P> for SetMeshViewBindGroup<I> {
    type Param = ();
    type ViewWorldQuery = (
        Read<ViewUniformOffset>,
        Read<ViewLightsUniformOffset>,
        Read<MeshViewBindGroup>,
    );
    type ItemWorldQuery = ();

    #[inline]
    fn render<'w>(
        _item: &P,
        (view_uniform, view_lights, mesh_view_bind_group): ROQueryItem<'w, Self::ViewWorldQuery>,
        _entity: (),
        _: SystemParamItem<'w, '_, Self::Param>,
        pass: &mut TrackedRenderPass<'w>,
    ) -> RenderCommandResult {
        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<P: PhaseItem, const I: usize> RenderCommand<P> for SetMeshBindGroup<I> {
    type Param = SRes<MeshBindGroup>;
    type ViewWorldQuery = ();
    type ItemWorldQuery = (
        Read<DynamicUniformIndex<MeshUniform>>,
        Option<Read<SkinnedMeshJoints>>,
    );
    #[inline]
    fn render<'w>(
        _item: &P,
        _view: (),
        (mesh_index, skinned_mesh_joints): ROQueryItem<'_, Self::ItemWorldQuery>,
        mesh_bind_group: SystemParamItem<'w, '_, Self::Param>,
        pass: &mut TrackedRenderPass<'w>,
    ) -> RenderCommandResult {
        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<P: PhaseItem> RenderCommand<P> for DrawMesh {
    type Param = SRes<RenderAssets<Mesh>>;
    type ViewWorldQuery = ();
    type ItemWorldQuery = Read<Handle<Mesh>>;
    #[inline]
    fn render<'w>(
        _item: &P,
        _view: (),
        mesh_handle: ROQueryItem<'_, Self::ItemWorldQuery>,
        meshes: SystemParamItem<'w, '_, Self::Param>,
        pass: &mut TrackedRenderPass<'w>,
    ) -> RenderCommandResult {
        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, 2, 4, 8, 16, 32, 64, 128] {
            assert_eq!(MeshPipelineKey::from_msaa_samples(i).msaa_samples(), i);
        }
    }
}