roast2d_internal 0.4.0

//! PBR (Physically Based Rendering) mesh shader.

use std::borrow::Cow;

use glam::Mat4;

use crate::engine::Engine;
use crate::platform::types::TextureResource;

use super::mesh::Mesh3D;
use super::shader_standard::Mesh3DShader;
use super::vertex::Mesh3DVertex;

/// Maximum lights for PBR (must match shader)
const PBR_MAX_LIGHTS: usize = 4;

/// Uniform data for PBR rendering (supports up to 4 lights)
#[repr(C)]
#[derive(Clone, Copy, bytemuck::Pod, bytemuck::Zeroable, Debug)]
struct PbrUniform {
    // Matrices
    mvp: [[f32; 4]; 4],
    model: [[f32; 4]; 4],
    // Camera
    camera_pos: [f32; 4],
    // PBR Material
    albedo: [f32; 4],
    pbr_params: [f32; 4], // x=metallic, y=roughness, z=ao, w=unused
    emissive: [f32; 4],
    // Lighting
    ambient: [f32; 4],
    // 4 lights - each light has: dir, color, pos (w=type), params (x=radius, y=inner, z=outer, w=intensity)
    light_dirs: [[f32; 4]; PBR_MAX_LIGHTS],
    light_colors: [[f32; 4]; PBR_MAX_LIGHTS],
    light_positions: [[f32; 4]; PBR_MAX_LIGHTS], // w = light type (0=dir, 1=point, 2=spot)
    light_params: [[f32; 4]; PBR_MAX_LIGHTS], // x=radius, y=inner_angle, z=outer_angle, w=intensity
    // Misc
    has_texture: f32,
    _padding: [f32; 3],
}

/// PBR draw command
#[derive(Clone)]
pub struct Draw3DPbr {
    /// The mesh to draw
    pub mesh: Mesh3D,
    /// Model transformation matrix
    pub model: Mat4,
    /// PBR material properties
    pub material: crate::light3d::PbrMaterial,
    /// Optional texture (albedo map)
    pub texture: Option<crate::handle::Handle>,
}

impl Draw3DPbr {
    /// Create a new PBR draw command
    pub fn new(mesh: Mesh3D, model: Mat4) -> Self {
        Self {
            mesh,
            model,
            material: crate::light3d::PbrMaterial::default(),
            texture: None,
        }
    }

    /// Set the PBR material
    pub fn with_material(mut self, material: crate::light3d::PbrMaterial) -> Self {
        self.material = material;
        self
    }

    /// Set the albedo texture
    pub fn with_texture(mut self, texture: crate::handle::Handle) -> Self {
        self.texture = Some(texture);
        self
    }
}

/// Maximum number of PBR draw calls per frame
const MAX_PBR_DRAWS: usize = 256;

/// PBR shader renderer using Cook-Torrance BRDF
pub struct Mesh3DPbrShader {
    pipeline: wgpu::RenderPipeline,
    uniform: wgpu::Buffer,
    uniform_alignment: u32,
    uniform_bind_group: wgpu::BindGroup,
    texture_bind_group_layout: wgpu::BindGroupLayout,
    default_texture_bind_group: wgpu::BindGroup,
    texture_bind_group_cache: hashbrown::HashMap<usize, wgpu::BindGroup>,
}

impl Mesh3DPbrShader {
    /// Create a PBR shader renderer
    pub fn new(g: &Engine) -> Self {
        let state = g.backend_state();
        let device = &state.device;
        let format = state.surface_view_format;

        let shader = device.create_shader_module(wgpu::ShaderModuleDescriptor {
            label: Some("mesh3d_pbr.shader"),
            source: wgpu::ShaderSource::Wgsl(Cow::Borrowed(include_str!(
                "../../assets/shaders/mesh3d_pbr.wgsl"
            ))),
        });

        let uniform_alignment = device.limits().min_uniform_buffer_offset_alignment;
        let uniform_size = std::mem::size_of::<PbrUniform>() as u32;
        let aligned_uniform_size = uniform_size.div_ceil(uniform_alignment) * uniform_alignment;

        let uniform = device.create_buffer(&wgpu::BufferDescriptor {
            label: Some("mesh3d_pbr.uniform"),
            size: (aligned_uniform_size as usize * MAX_PBR_DRAWS) as u64,
            usage: wgpu::BufferUsages::UNIFORM | wgpu::BufferUsages::COPY_DST,
            mapped_at_creation: false,
        });

        let uniform_bind_group_layout =
            device.create_bind_group_layout(&wgpu::BindGroupLayoutDescriptor {
                label: Some("mesh3d_pbr.uniform_bgl"),
                entries: &[wgpu::BindGroupLayoutEntry {
                    binding: 0,
                    visibility: wgpu::ShaderStages::VERTEX | wgpu::ShaderStages::FRAGMENT,
                    ty: wgpu::BindingType::Buffer {
                        ty: wgpu::BufferBindingType::Uniform,
                        has_dynamic_offset: true,
                        min_binding_size: wgpu::BufferSize::new(uniform_size as u64),
                    },
                    count: None,
                }],
            });

        let uniform_bind_group = device.create_bind_group(&wgpu::BindGroupDescriptor {
            label: Some("mesh3d_pbr.uniform_bg"),
            layout: &uniform_bind_group_layout,
            entries: &[wgpu::BindGroupEntry {
                binding: 0,
                resource: wgpu::BindingResource::Buffer(wgpu::BufferBinding {
                    buffer: &uniform,
                    offset: 0,
                    size: wgpu::BufferSize::new(uniform_size as u64),
                }),
            }],
        });

        let texture_bind_group_layout =
            device.create_bind_group_layout(&wgpu::BindGroupLayoutDescriptor {
                label: Some("mesh3d_pbr.texture_bgl"),
                entries: &[
                    wgpu::BindGroupLayoutEntry {
                        binding: 0,
                        visibility: wgpu::ShaderStages::FRAGMENT,
                        ty: wgpu::BindingType::Texture {
                            sample_type: wgpu::TextureSampleType::Float { filterable: true },
                            view_dimension: wgpu::TextureViewDimension::D2,
                            multisampled: false,
                        },
                        count: None,
                    },
                    wgpu::BindGroupLayoutEntry {
                        binding: 1,
                        visibility: wgpu::ShaderStages::FRAGMENT,
                        ty: wgpu::BindingType::Sampler(wgpu::SamplerBindingType::Filtering),
                        count: None,
                    },
                ],
            });

        let default_texture = Mesh3DShader::create_default_texture(device, &state.queue);
        let default_texture_bind_group = device.create_bind_group(&wgpu::BindGroupDescriptor {
            label: Some("mesh3d_pbr.default_texture_bg"),
            layout: &texture_bind_group_layout,
            entries: &[
                wgpu::BindGroupEntry {
                    binding: 0,
                    resource: wgpu::BindingResource::TextureView(&default_texture.view),
                },
                wgpu::BindGroupEntry {
                    binding: 1,
                    resource: wgpu::BindingResource::Sampler(&default_texture.sampler),
                },
            ],
        });

        let pipeline_layout = device.create_pipeline_layout(&wgpu::PipelineLayoutDescriptor {
            label: Some("mesh3d_pbr.pipeline_layout"),
            bind_group_layouts: &[&uniform_bind_group_layout, &texture_bind_group_layout],
            push_constant_ranges: &[],
        });

        let pipeline = device.create_render_pipeline(&wgpu::RenderPipelineDescriptor {
            label: Some("mesh3d_pbr.pipeline"),
            layout: Some(&pipeline_layout),
            vertex: wgpu::VertexState {
                module: &shader,
                entry_point: Some("vs_main"),
                compilation_options: Default::default(),
                buffers: &[wgpu::VertexBufferLayout {
                    array_stride: std::mem::size_of::<Mesh3DVertex>() as wgpu::BufferAddress,
                    step_mode: wgpu::VertexStepMode::Vertex,
                    attributes: &wgpu::vertex_attr_array![0 => Float32x3, 1 => Float32x3, 2 => Float32x2],
                }],
            },
            fragment: Some(wgpu::FragmentState {
                module: &shader,
                entry_point: Some("fs_main"),
                compilation_options: Default::default(),
                targets: &[Some(wgpu::ColorTargetState {
                    format,
                    blend: None,
                    write_mask: wgpu::ColorWrites::ALL,
                })],
            }),
            primitive: wgpu::PrimitiveState {
                topology: wgpu::PrimitiveTopology::TriangleList,
                strip_index_format: None,
                front_face: wgpu::FrontFace::Ccw,
                cull_mode: Some(wgpu::Face::Back),
                unclipped_depth: false,
                polygon_mode: wgpu::PolygonMode::Fill,
                conservative: false,
            },
            depth_stencil: Some(wgpu::DepthStencilState {
                format: wgpu::TextureFormat::Depth32Float,
                depth_write_enabled: true,
                depth_compare: wgpu::CompareFunction::Greater,
                stencil: wgpu::StencilState::default(),
                bias: wgpu::DepthBiasState::default(),
            }),
            multisample: wgpu::MultisampleState::default(),
            multiview: None,
            cache: None,
        });

        Self {
            pipeline,
            uniform,
            uniform_alignment,
            uniform_bind_group,
            texture_bind_group_layout,
            default_texture_bind_group,
            texture_bind_group_cache: hashbrown::HashMap::new(),
        }
    }

    /// Clear cached bind groups at frame start
    pub fn frame_start(&mut self) {
        self.texture_bind_group_cache.clear();
    }

    fn create_texture_bind_group(
        &mut self,
        device: &wgpu::Device,
        texture: &TextureResource,
    ) -> wgpu::BindGroup {
        let key = &texture.view as *const _ as usize;
        if let Some(bg) = self.texture_bind_group_cache.get(&key) {
            return bg.clone();
        }
        let bg = device.create_bind_group(&wgpu::BindGroupDescriptor {
            label: Some("mesh3d_pbr.texture_bg"),
            layout: &self.texture_bind_group_layout,
            entries: &[
                wgpu::BindGroupEntry {
                    binding: 0,
                    resource: wgpu::BindingResource::TextureView(&texture.view),
                },
                wgpu::BindGroupEntry {
                    binding: 1,
                    resource: wgpu::BindingResource::Sampler(&texture.sampler),
                },
            ],
        });
        self.texture_bind_group_cache.insert(key, bg.clone());
        bg
    }

    /// Record PBR draw commands
    #[allow(clippy::too_many_arguments)]
    pub fn record(
        &mut self,
        g: &Engine,
        color_target: &wgpu::Texture,
        depth_view: &wgpu::TextureView,
        view_proj: Mat4,
        draws: &[(
            &Mesh3D,
            Mat4,
            Option<&TextureResource>,
            &crate::light3d::PbrMaterial,
        )],
        encoder: &mut wgpu::CommandEncoder,
        should_clear: bool,
    ) {
        if draws.is_empty() {
            return;
        }

        let state = g.backend_state();
        let camera = g.camera3d();
        let lighting = g.lighting();

        // Get aligned uniform size
        let uniform_size = std::mem::size_of::<PbrUniform>() as u32;
        let aligned_uniform_size =
            uniform_size.div_ceil(self.uniform_alignment) * self.uniform_alignment;

        // Collect all lights (up to PBR_MAX_LIGHTS)
        let mut light_dirs = [[0.0f32; 4]; PBR_MAX_LIGHTS];
        let mut light_colors = [[0.0f32; 4]; PBR_MAX_LIGHTS];
        let mut light_positions = [[0.0f32; 4]; PBR_MAX_LIGHTS];
        let mut light_params_arr = [[0.0f32; 4]; PBR_MAX_LIGHTS];

        for (i, light_opt) in lighting.lights.iter().enumerate() {
            if i >= PBR_MAX_LIGHTS {
                break;
            }
            if let Some(light) = light_opt
                && light.enabled
            {
                let (light_type, radius, inner, outer) = match light.kind {
                    crate::light3d::LightKind::Directional => (0.0, 0.0, 0.0, 0.0),
                    crate::light3d::LightKind::Point { radius } => (1.0, radius, 0.0, 0.0),
                    crate::light3d::LightKind::Spot {
                        radius,
                        inner_angle,
                        outer_angle,
                    } => (2.0, radius, inner_angle.cos(), outer_angle.cos()),
                };
                light_dirs[i] = [light.direction.x, light.direction.y, light.direction.z, 0.0];
                light_colors[i] = [light.color.r, light.color.g, light.color.b, light.color.a];
                light_positions[i] = [
                    light.position.x,
                    light.position.y,
                    light.position.z,
                    light_type,
                ];
                light_params_arr[i] = [radius, inner, outer, light.intensity];
            }
        }

        // Prepare uniforms for each draw
        let mut uniform_data = Vec::with_capacity(draws.len() * aligned_uniform_size as usize);
        for (_, model, texture_res, material) in draws.iter() {
            let mvp = view_proj * *model;
            let has_texture = if texture_res.is_some() {
                1.0f32
            } else {
                0.0f32
            };

            let u = PbrUniform {
                mvp: mvp.to_cols_array_2d(),
                model: model.to_cols_array_2d(),
                camera_pos: [camera.eye.x, camera.eye.y, camera.eye.z, 0.0],
                albedo: [
                    material.albedo.r,
                    material.albedo.g,
                    material.albedo.b,
                    material.albedo.a,
                ],
                pbr_params: [material.metallic, material.roughness, material.ao, 0.0],
                emissive: [
                    material.emissive.r,
                    material.emissive.g,
                    material.emissive.b,
                    material.emissive.a,
                ],
                ambient: [
                    lighting.ambient.r,
                    lighting.ambient.g,
                    lighting.ambient.b,
                    lighting.ambient.a,
                ],
                light_dirs,
                light_colors,
                light_positions,
                light_params: light_params_arr,
                has_texture,
                _padding: [0.0; 3],
            };

            uniform_data.extend_from_slice(bytemuck::bytes_of(&u));
            // Pad to alignment
            let padding = aligned_uniform_size as usize - std::mem::size_of::<PbrUniform>();
            uniform_data.extend(std::iter::repeat_n(0u8, padding));
        }
        state.queue.write_buffer(&self.uniform, 0, &uniform_data);

        // Begin render pass
        let color_view = color_target.create_view(&wgpu::TextureViewDescriptor::default());
        let (color_load, depth_load) = if should_clear {
            (
                wgpu::LoadOp::Clear(wgpu::Color::TRANSPARENT),
                wgpu::LoadOp::Clear(0.0),
            )
        } else {
            (wgpu::LoadOp::Load, wgpu::LoadOp::Load)
        };

        let mut pass = encoder.begin_render_pass(&wgpu::RenderPassDescriptor {
            label: Some("mesh3d_pbr.pass"),
            color_attachments: &[Some(wgpu::RenderPassColorAttachment {
                view: &color_view,
                resolve_target: None,
                ops: wgpu::Operations {
                    load: color_load,
                    store: wgpu::StoreOp::Store,
                },
                depth_slice: None,
            })],
            depth_stencil_attachment: Some(wgpu::RenderPassDepthStencilAttachment {
                view: depth_view,
                depth_ops: Some(wgpu::Operations {
                    load: depth_load,
                    store: wgpu::StoreOp::Store,
                }),
                stencil_ops: None,
            }),
            occlusion_query_set: None,
            timestamp_writes: None,
        });

        pass.set_pipeline(&self.pipeline);

        for (i, (mesh, _, texture_res, _)) in draws.iter().enumerate() {
            let offset = i as u32 * aligned_uniform_size;
            pass.set_bind_group(0, &self.uniform_bind_group, &[offset]);

            if let Some(tex_res) = texture_res {
                let tex_bg = self.create_texture_bind_group(&state.device, tex_res);
                pass.set_bind_group(1, &tex_bg, &[]);
            } else {
                pass.set_bind_group(1, &self.default_texture_bind_group, &[]);
            }

            pass.set_vertex_buffer(0, mesh.vertex.slice(..));
            pass.set_index_buffer(mesh.index.slice(..), wgpu::IndexFormat::Uint16);
            pass.draw_indexed(0..mesh.index_count, 0, 0..1);
        }
    }
}