polyscope_render/

tone_mapping.rs

//! Tone mapping post-processing pass.

use std::num::NonZeroU64;
use wgpu::util::DeviceExt;

/// GPU representation of tone mapping uniforms.
#[repr(C)]
#[derive(Debug, Clone, Copy, bytemuck::Pod, bytemuck::Zeroable)]
pub struct ToneMapUniforms {
    pub exposure: f32,
    pub white_level: f32,
    pub gamma: f32,
    pub ssao_enabled: u32, // 0 = disabled, 1 = enabled
    /// Padding to 32 bytes (workaround for wgpu late binding size validation).
    #[allow(clippy::pub_underscore_fields)]
    pub _padding: [f32; 4],
}

impl Default for ToneMapUniforms {
    fn default() -> Self {
        Self {
            exposure: 1.0,
            white_level: 1.0,
            gamma: 2.2,
            ssao_enabled: 0,
            _padding: [0.0; 4],
        }
    }
}

/// Tone mapping render resources.
pub struct ToneMapPass {
    pipeline: wgpu::RenderPipeline,
    bind_group_layout: wgpu::BindGroupLayout,
    uniform_buffer: wgpu::Buffer,
    sampler: wgpu::Sampler,
}

impl ToneMapPass {
    /// Creates a new tone mapping pass.
    #[must_use]
    pub fn new(device: &wgpu::Device, output_format: wgpu::TextureFormat) -> Self {
        // Create bind group layout
        let bind_group_layout = device.create_bind_group_layout(&wgpu::BindGroupLayoutDescriptor {
            label: Some("Tone Map Bind Group Layout"),
            entries: &[
                // Input texture
                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,
                },
                // Sampler
                wgpu::BindGroupLayoutEntry {
                    binding: 1,
                    visibility: wgpu::ShaderStages::FRAGMENT,
                    ty: wgpu::BindingType::Sampler(wgpu::SamplerBindingType::Filtering),
                    count: None,
                },
                // Uniforms
                wgpu::BindGroupLayoutEntry {
                    binding: 2,
                    visibility: wgpu::ShaderStages::FRAGMENT,
                    ty: wgpu::BindingType::Buffer {
                        ty: wgpu::BufferBindingType::Uniform,
                        has_dynamic_offset: false,
                        min_binding_size: NonZeroU64::new(32),
                    },
                    count: None,
                },
                // SSAO texture
                wgpu::BindGroupLayoutEntry {
                    binding: 3,
                    visibility: wgpu::ShaderStages::FRAGMENT,
                    ty: wgpu::BindingType::Texture {
                        sample_type: wgpu::TextureSampleType::Float { filterable: true },
                        view_dimension: wgpu::TextureViewDimension::D2,
                        multisampled: false,
                    },
                    count: None,
                },
            ],
        });

        // Create shader
        let shader = device.create_shader_module(wgpu::ShaderModuleDescriptor {
            label: Some("Tone Map Shader"),
            source: wgpu::ShaderSource::Wgsl(include_str!("shaders/tone_map.wgsl").into()),
        });

        // Create pipeline layout
        let pipeline_layout = device.create_pipeline_layout(&wgpu::PipelineLayoutDescriptor {
            label: Some("Tone Map Pipeline Layout"),
            bind_group_layouts: &[&bind_group_layout],
            push_constant_ranges: &[],
        });

        // Create render pipeline
        let pipeline = device.create_render_pipeline(&wgpu::RenderPipelineDescriptor {
            label: Some("Tone Map Pipeline"),
            layout: Some(&pipeline_layout),
            vertex: wgpu::VertexState {
                module: &shader,
                entry_point: Some("vs_main"),
                buffers: &[],
                compilation_options: wgpu::PipelineCompilationOptions::default(),
            },
            fragment: Some(wgpu::FragmentState {
                module: &shader,
                entry_point: Some("fs_main"),
                targets: &[Some(wgpu::ColorTargetState {
                    format: output_format,
                    blend: None,
                    write_mask: wgpu::ColorWrites::ALL,
                })],
                compilation_options: wgpu::PipelineCompilationOptions::default(),
            }),
            primitive: wgpu::PrimitiveState {
                topology: wgpu::PrimitiveTopology::TriangleList,
                ..Default::default()
            },
            depth_stencil: None,
            multisample: wgpu::MultisampleState::default(),
            multiview: None,
            cache: None,
        });

        // Create uniform buffer
        let uniforms = ToneMapUniforms::default();
        let uniform_buffer = device.create_buffer_init(&wgpu::util::BufferInitDescriptor {
            label: Some("Tone Map Uniform Buffer"),
            contents: bytemuck::cast_slice(&[uniforms]),
            usage: wgpu::BufferUsages::UNIFORM | wgpu::BufferUsages::COPY_DST,
        });

        // Create sampler
        let sampler = device.create_sampler(&wgpu::SamplerDescriptor {
            label: Some("Tone Map Sampler"),
            mag_filter: wgpu::FilterMode::Linear,
            min_filter: wgpu::FilterMode::Linear,
            ..Default::default()
        });

        Self {
            pipeline,
            bind_group_layout,
            uniform_buffer,
            sampler,
        }
    }

    /// Updates the tone mapping uniforms.
    pub fn update_uniforms(
        &self,
        queue: &wgpu::Queue,
        exposure: f32,
        white_level: f32,
        gamma: f32,
        ssao_enabled: bool,
    ) {
        let uniforms = ToneMapUniforms {
            exposure,
            white_level,
            gamma,
            ssao_enabled: u32::from(ssao_enabled),
            _padding: [0.0; 4],
        };
        queue.write_buffer(&self.uniform_buffer, 0, bytemuck::cast_slice(&[uniforms]));
    }

    /// Creates a bind group for rendering.
    #[must_use]
    pub fn create_bind_group(
        &self,
        device: &wgpu::Device,
        input_view: &wgpu::TextureView,
        ssao_view: &wgpu::TextureView,
    ) -> wgpu::BindGroup {
        device.create_bind_group(&wgpu::BindGroupDescriptor {
            label: Some("Tone Map Bind Group"),
            layout: &self.bind_group_layout,
            entries: &[
                wgpu::BindGroupEntry {
                    binding: 0,
                    resource: wgpu::BindingResource::TextureView(input_view),
                },
                wgpu::BindGroupEntry {
                    binding: 1,
                    resource: wgpu::BindingResource::Sampler(&self.sampler),
                },
                wgpu::BindGroupEntry {
                    binding: 2,
                    resource: self.uniform_buffer.as_entire_binding(),
                },
                wgpu::BindGroupEntry {
                    binding: 3,
                    resource: wgpu::BindingResource::TextureView(ssao_view),
                },
            ],
        })
    }

    /// Renders the tone mapping pass.
    pub fn render(
        &self,
        encoder: &mut wgpu::CommandEncoder,
        output_view: &wgpu::TextureView,
        bind_group: &wgpu::BindGroup,
    ) {
        let mut render_pass = encoder.begin_render_pass(&wgpu::RenderPassDescriptor {
            label: Some("Tone Map Pass"),
            color_attachments: &[Some(wgpu::RenderPassColorAttachment {
                view: output_view,
                resolve_target: None,
                ops: wgpu::Operations {
                    load: wgpu::LoadOp::Clear(wgpu::Color::BLACK),
                    store: wgpu::StoreOp::Store,
                },
                depth_slice: None,
            })],
            depth_stencil_attachment: None,
            ..Default::default()
        });

        render_pass.set_pipeline(&self.pipeline);
        render_pass.set_bind_group(0, bind_group, &[]);
        render_pass.draw(0..3, 0..1); // Fullscreen triangle
    }

    /// Renders tone mapping from input HDR texture to output texture.
    /// Convenience method that creates a bind group and renders in one call.
    pub fn render_to_target(
        &self,
        device: &wgpu::Device,
        encoder: &mut wgpu::CommandEncoder,
        input_view: &wgpu::TextureView,
        ssao_view: &wgpu::TextureView,
        output_view: &wgpu::TextureView,
    ) {
        let bind_group = self.create_bind_group(device, input_view, ssao_view);
        self.render(encoder, output_view, &bind_group);
    }
}