681 lines
25 KiB
Rust
681 lines
25 KiB
Rust
//! wgpu resources for the fractal: the render pipeline, the uniform buffer, the
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//! reference-orbit storage buffer, and the egui paint callback that drives them.
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//!
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//! Rendering strategy: the expensive per-pixel perturbation shader renders into
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//! an offscreen **cache texture**, and only when the view/coloring/size actually
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//! change (tracked by `rendered`). Every egui frame then just blits that cached
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//! texture onto egui's surface with a cheap textured fullscreen triangle — so
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//! incidental repaints (mouse-move, hover, the worker-pending poll) cost a blit,
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//! not a full fractal recompute. The fragment shader iterates each pixel as an
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//! f32 perturbation delta from the reference orbit stored in `ref_buffer`.
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use std::sync::Arc;
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use eframe::egui_wgpu::{self, wgpu};
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/// Maximum reference-orbit length (points) the storage buffer can hold. Also
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/// bounds the iteration count. 128k points * 8 bytes = 1 MiB.
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pub const MAX_REF_POINTS: usize = 1 << 17;
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/// GPU-side view + coloring parameters. Layout must match `Uniforms` in the
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/// WGSL shader; total size is a multiple of 16 bytes for uniform-buffer rules.
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#[repr(C)]
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#[derive(Copy, Clone, bytemuck::Pod, bytemuck::Zeroable)]
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pub struct Uniforms {
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/// Complex-plane span (width, height) covered by the view. Per-pixel `dc`
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/// is `centered * span`, where `centered` is in [-0.5, 0.5].
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pub span: [f32; 2],
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pub max_iter: u32,
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pub ref_len: u32,
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pub color_offset: f32,
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pub color_scale: f32,
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pub bailout_sq: f32,
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/// 0 = Mandelbrot, 1 = Julia.
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pub is_julia: u32,
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pub palette_id: u32,
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/// Supersampling factor per axis: 1 = off, 2 = 2×2 (4 samples).
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pub aa_level: u32,
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/// Iteration formula (`FractalKind::shader_id`).
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pub kind: u32,
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/// Exponent for the Multibrot kind.
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pub power: u32,
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/// Complex offset of the view center from the reference center, so a stale
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/// or reused reference (computed at a slightly different center) still maps
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/// correctly. Added to every pixel's per-pixel offset.
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pub dc_offset: [f32; 2],
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/// 0 = escape-time coloring, 1 = distance-estimation shading.
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pub de_coloring: u32,
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/// Padding to a 16-byte multiple (uniform buffer requirement).
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pub _pad: u32,
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}
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/// Offscreen texture the fractal is rendered into, plus the bind group used to
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/// blit it. Recreated whenever the widget's pixel size changes.
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struct CacheTarget {
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view: wgpu::TextureView,
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blit_bind_group: wgpu::BindGroup,
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width: u32,
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height: u32,
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}
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/// State the cache texture was last rendered with. If the next frame's inputs
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/// match this, the cache is still valid and the fractal shader is skipped.
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struct RenderedState {
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uniforms: Uniforms,
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generation: u64,
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width: u32,
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height: u32,
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}
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pub struct FractalRenderer {
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pipeline: wgpu::RenderPipeline,
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bind_group_layout: wgpu::BindGroupLayout,
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uniform_buffer: wgpu::Buffer,
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ref_buffer: wgpu::Buffer,
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bind_group: wgpu::BindGroup,
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target_format: wgpu::TextureFormat,
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/// Generation of the reference orbit currently uploaded to `ref_buffer`.
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uploaded_generation: u64,
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/// Blit pipeline + resources that copy the cache texture to egui's surface.
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blit_pipeline: wgpu::RenderPipeline,
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blit_bind_group_layout: wgpu::BindGroupLayout,
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blit_sampler: wgpu::Sampler,
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/// The offscreen cache; `None` until the first frame sizes it.
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cache: Option<CacheTarget>,
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/// What the cache currently holds; `None` forces a re-render.
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rendered: Option<RenderedState>,
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}
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impl FractalRenderer {
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pub fn new(device: &wgpu::Device, target_format: wgpu::TextureFormat) -> Self {
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let shader = device.create_shader_module(wgpu::ShaderModuleDescriptor {
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label: Some("mandelbrot"),
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source: wgpu::ShaderSource::Wgsl(include_str!("../shaders/mandelbrot.wgsl").into()),
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});
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let uniform_buffer = device.create_buffer(&wgpu::BufferDescriptor {
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label: Some("fractal uniforms"),
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size: std::mem::size_of::<Uniforms>() as u64,
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usage: wgpu::BufferUsages::UNIFORM | wgpu::BufferUsages::COPY_DST,
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mapped_at_creation: false,
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});
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let ref_buffer = device.create_buffer(&wgpu::BufferDescriptor {
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label: Some("reference orbit"),
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size: (MAX_REF_POINTS * std::mem::size_of::<[f32; 2]>()) as u64,
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usage: wgpu::BufferUsages::STORAGE | wgpu::BufferUsages::COPY_DST,
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mapped_at_creation: false,
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});
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let bind_group_layout = device.create_bind_group_layout(&wgpu::BindGroupLayoutDescriptor {
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label: Some("fractal bind group layout"),
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entries: &[
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wgpu::BindGroupLayoutEntry {
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binding: 0,
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visibility: wgpu::ShaderStages::FRAGMENT,
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ty: wgpu::BindingType::Buffer {
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ty: wgpu::BufferBindingType::Uniform,
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has_dynamic_offset: false,
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min_binding_size: None,
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},
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count: None,
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},
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wgpu::BindGroupLayoutEntry {
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binding: 1,
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visibility: wgpu::ShaderStages::FRAGMENT,
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ty: wgpu::BindingType::Buffer {
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ty: wgpu::BufferBindingType::Storage { read_only: true },
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has_dynamic_offset: false,
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min_binding_size: None,
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},
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count: None,
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},
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],
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});
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let bind_group = device.create_bind_group(&wgpu::BindGroupDescriptor {
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label: Some("fractal bind group"),
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layout: &bind_group_layout,
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entries: &[
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wgpu::BindGroupEntry {
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binding: 0,
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resource: uniform_buffer.as_entire_binding(),
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},
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wgpu::BindGroupEntry {
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binding: 1,
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resource: ref_buffer.as_entire_binding(),
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},
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],
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});
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let pipeline_layout = device.create_pipeline_layout(&wgpu::PipelineLayoutDescriptor {
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label: Some("fractal pipeline layout"),
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bind_group_layouts: &[Some(&bind_group_layout)],
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immediate_size: 0,
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});
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let pipeline = device.create_render_pipeline(&wgpu::RenderPipelineDescriptor {
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label: Some("fractal pipeline"),
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layout: Some(&pipeline_layout),
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vertex: wgpu::VertexState {
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module: &shader,
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entry_point: Some("vs_main"),
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buffers: &[],
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compilation_options: Default::default(),
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},
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fragment: Some(wgpu::FragmentState {
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module: &shader,
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entry_point: Some("fs_main"),
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targets: &[Some(wgpu::ColorTargetState {
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format: target_format,
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blend: None,
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write_mask: wgpu::ColorWrites::ALL,
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})],
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compilation_options: Default::default(),
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}),
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primitive: wgpu::PrimitiveState::default(),
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depth_stencil: None,
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multisample: wgpu::MultisampleState::default(),
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multiview_mask: None,
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cache: None,
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});
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// Blit pipeline: samples the cache texture onto egui's surface.
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let blit_shader = device.create_shader_module(wgpu::ShaderModuleDescriptor {
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label: Some("blit"),
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source: wgpu::ShaderSource::Wgsl(include_str!("../shaders/blit.wgsl").into()),
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});
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let blit_bind_group_layout =
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device.create_bind_group_layout(&wgpu::BindGroupLayoutDescriptor {
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label: Some("blit bind group layout"),
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entries: &[
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wgpu::BindGroupLayoutEntry {
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binding: 0,
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visibility: wgpu::ShaderStages::FRAGMENT,
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ty: wgpu::BindingType::Texture {
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sample_type: wgpu::TextureSampleType::Float { filterable: true },
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view_dimension: wgpu::TextureViewDimension::D2,
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multisampled: false,
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},
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count: None,
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},
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wgpu::BindGroupLayoutEntry {
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binding: 1,
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visibility: wgpu::ShaderStages::FRAGMENT,
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ty: wgpu::BindingType::Sampler(wgpu::SamplerBindingType::Filtering),
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count: None,
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},
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],
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});
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let blit_sampler = device.create_sampler(&wgpu::SamplerDescriptor {
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label: Some("blit sampler"),
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mag_filter: wgpu::FilterMode::Linear,
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min_filter: wgpu::FilterMode::Linear,
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..Default::default()
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});
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let blit_pipeline_layout = device.create_pipeline_layout(&wgpu::PipelineLayoutDescriptor {
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label: Some("blit pipeline layout"),
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bind_group_layouts: &[Some(&blit_bind_group_layout)],
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immediate_size: 0,
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});
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let blit_pipeline = device.create_render_pipeline(&wgpu::RenderPipelineDescriptor {
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label: Some("blit pipeline"),
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layout: Some(&blit_pipeline_layout),
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vertex: wgpu::VertexState {
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module: &blit_shader,
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entry_point: Some("vs_main"),
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buffers: &[],
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compilation_options: Default::default(),
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},
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fragment: Some(wgpu::FragmentState {
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module: &blit_shader,
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entry_point: Some("fs_main"),
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targets: &[Some(wgpu::ColorTargetState {
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format: target_format,
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blend: None,
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write_mask: wgpu::ColorWrites::ALL,
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})],
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compilation_options: Default::default(),
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}),
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primitive: wgpu::PrimitiveState::default(),
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depth_stencil: None,
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multisample: wgpu::MultisampleState::default(),
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multiview_mask: None,
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cache: None,
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});
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Self {
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pipeline,
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bind_group_layout,
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uniform_buffer,
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ref_buffer,
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bind_group,
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target_format,
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uploaded_generation: u64::MAX,
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blit_pipeline,
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blit_bind_group_layout,
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blit_sampler,
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cache: None,
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rendered: None,
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}
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}
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/// Ensure the cache texture exists at `width`×`height`. Recreates it (and its
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/// blit bind group) on a size change, invalidating any previous render.
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fn ensure_cache(&mut self, device: &wgpu::Device, width: u32, height: u32) {
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if let Some(c) = &self.cache
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&& c.width == width
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&& c.height == height
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{
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return;
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}
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let texture = device.create_texture(&wgpu::TextureDescriptor {
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label: Some("fractal cache"),
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size: wgpu::Extent3d {
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width,
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height,
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depth_or_array_layers: 1,
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},
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mip_level_count: 1,
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sample_count: 1,
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dimension: wgpu::TextureDimension::D2,
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format: self.target_format,
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usage: wgpu::TextureUsages::RENDER_ATTACHMENT | wgpu::TextureUsages::TEXTURE_BINDING,
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view_formats: &[],
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});
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let view = texture.create_view(&wgpu::TextureViewDescriptor::default());
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let blit_bind_group = device.create_bind_group(&wgpu::BindGroupDescriptor {
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label: Some("blit bind group"),
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layout: &self.blit_bind_group_layout,
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entries: &[
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wgpu::BindGroupEntry {
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binding: 0,
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resource: wgpu::BindingResource::TextureView(&view),
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},
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wgpu::BindGroupEntry {
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binding: 1,
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resource: wgpu::BindingResource::Sampler(&self.blit_sampler),
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},
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],
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});
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self.cache = Some(CacheTarget {
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view,
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blit_bind_group,
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width,
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height,
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});
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// New texture → old render is gone.
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self.rendered = None;
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}
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/// Handles needed to build a standalone [`ExportRender`] off the UI thread:
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/// the (immutable) pipeline and its bind-group layout, plus the target
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/// format. Cloned so the caller can drop the render-state lock before use.
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pub fn export_handles(&self) -> (wgpu::RenderPipeline, wgpu::BindGroupLayout, wgpu::TextureFormat) {
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(
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self.pipeline.clone(),
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self.bind_group_layout.clone(),
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self.target_format,
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)
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}
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}
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/// A self-contained render of one export image. It owns its own uniform and
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/// reference buffers (a snapshot of the view at export time), so it is unaffected
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/// by panning/zooming on the main thread, and can run on a background thread.
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/// The image is rendered in horizontal tiles so progress can be reported as the
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/// GPU works through it.
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pub struct ExportRender {
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pipeline: wgpu::RenderPipeline,
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bind_group: wgpu::BindGroup,
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texture: wgpu::Texture,
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view: wgpu::TextureView,
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readback: wgpu::Buffer,
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/// Padded bytes-per-row of the readback buffer.
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pub padded_bpr: u32,
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pub width: u32,
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pub height: u32,
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/// Number of horizontal tiles the render is split into.
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pub tiles: u32,
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pub swap_rb: bool,
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}
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impl ExportRender {
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/// Allocate the export's dedicated GPU resources and upload the snapshot.
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#[allow(clippy::too_many_arguments)]
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pub fn new(
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device: &wgpu::Device,
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queue: &wgpu::Queue,
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pipeline: wgpu::RenderPipeline,
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bind_group_layout: &wgpu::BindGroupLayout,
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target_format: wgpu::TextureFormat,
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width: u32,
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height: u32,
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uniforms: Uniforms,
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reference: &[[f32; 2]],
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) -> Self {
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let uniform_buffer = device.create_buffer(&wgpu::BufferDescriptor {
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label: Some("export uniforms"),
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size: std::mem::size_of::<Uniforms>() as u64,
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usage: wgpu::BufferUsages::UNIFORM | wgpu::BufferUsages::COPY_DST,
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mapped_at_creation: false,
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});
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queue.write_buffer(&uniform_buffer, 0, bytemuck::bytes_of(&uniforms));
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let count = reference.len().min(MAX_REF_POINTS);
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let ref_buffer = device.create_buffer(&wgpu::BufferDescriptor {
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label: Some("export reference orbit"),
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size: (count.max(1) * std::mem::size_of::<[f32; 2]>()) as u64,
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usage: wgpu::BufferUsages::STORAGE | wgpu::BufferUsages::COPY_DST,
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mapped_at_creation: false,
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});
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if count > 0 {
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queue.write_buffer(&ref_buffer, 0, bytemuck::cast_slice(&reference[..count]));
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}
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let bind_group = device.create_bind_group(&wgpu::BindGroupDescriptor {
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label: Some("export bind group"),
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layout: bind_group_layout,
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entries: &[
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wgpu::BindGroupEntry {
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binding: 0,
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resource: uniform_buffer.as_entire_binding(),
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},
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wgpu::BindGroupEntry {
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binding: 1,
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resource: ref_buffer.as_entire_binding(),
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},
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],
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});
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let texture = device.create_texture(&wgpu::TextureDescriptor {
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label: Some("export target"),
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size: wgpu::Extent3d {
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width,
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height,
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depth_or_array_layers: 1,
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},
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mip_level_count: 1,
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sample_count: 1,
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dimension: wgpu::TextureDimension::D2,
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format: target_format,
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usage: wgpu::TextureUsages::RENDER_ATTACHMENT | wgpu::TextureUsages::COPY_SRC,
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view_formats: &[],
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});
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let view = texture.create_view(&wgpu::TextureViewDescriptor::default());
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let align = wgpu::COPY_BYTES_PER_ROW_ALIGNMENT;
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let padded_bpr = (width * 4).div_ceil(align) * align;
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let readback = device.create_buffer(&wgpu::BufferDescriptor {
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label: Some("export readback"),
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size: (padded_bpr * height) as u64,
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usage: wgpu::BufferUsages::COPY_DST | wgpu::BufferUsages::MAP_READ,
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mapped_at_creation: false,
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});
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// ~128px bands, kept to a sane range so progress is smooth without too
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// many submissions.
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let tiles = (height / 128).clamp(8, 64).min(height.max(1));
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let swap_rb = matches!(
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target_format,
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wgpu::TextureFormat::Bgra8Unorm | wgpu::TextureFormat::Bgra8UnormSrgb
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);
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Self {
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pipeline,
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bind_group,
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texture,
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view,
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readback,
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padded_bpr,
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width,
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height,
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tiles,
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swap_rb,
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}
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}
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/// Pixel row range `[y0, y1)` covered by tile `t`.
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fn tile_rows(&self, t: u32) -> (u32, u32) {
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let band = self.height.div_ceil(self.tiles);
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let y0 = (t * band).min(self.height);
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let y1 = (y0 + band).min(self.height);
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(y0, y1)
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}
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/// Render one horizontal tile into the export texture and submit it. Tile 0
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/// clears the whole attachment; later tiles preserve earlier ones.
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pub fn render_tile(&self, device: &wgpu::Device, queue: &wgpu::Queue, t: u32) {
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let (y0, y1) = self.tile_rows(t);
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if y1 <= y0 {
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return;
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}
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let load = if t == 0 {
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wgpu::LoadOp::Clear(wgpu::Color::BLACK)
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} else {
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wgpu::LoadOp::Load
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};
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let mut encoder = device.create_command_encoder(&wgpu::CommandEncoderDescriptor {
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label: Some("export tile"),
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});
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{
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let mut pass = encoder.begin_render_pass(&wgpu::RenderPassDescriptor {
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label: Some("export tile pass"),
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color_attachments: &[Some(wgpu::RenderPassColorAttachment {
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view: &self.view,
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depth_slice: None,
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resolve_target: None,
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ops: wgpu::Operations {
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load,
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store: wgpu::StoreOp::Store,
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},
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})],
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depth_stencil_attachment: None,
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timestamp_writes: None,
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occlusion_query_set: None,
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multiview_mask: None,
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});
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// Full-viewport triangle (so pixel→plane mapping matches the whole
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// image), scissored to this tile's rows.
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pass.set_scissor_rect(0, y0, self.width, y1 - y0);
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pass.set_pipeline(&self.pipeline);
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pass.set_bind_group(0, &self.bind_group, &[]);
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||
pass.draw(0..3, 0..1);
|
||
}
|
||
queue.submit(std::iter::once(encoder.finish()));
|
||
}
|
||
|
||
/// Copy the finished texture into the mappable readback buffer and submit.
|
||
pub fn copy_to_readback(&self, device: &wgpu::Device, queue: &wgpu::Queue) {
|
||
let mut encoder = device.create_command_encoder(&wgpu::CommandEncoderDescriptor {
|
||
label: Some("export copy"),
|
||
});
|
||
encoder.copy_texture_to_buffer(
|
||
wgpu::TexelCopyTextureInfo {
|
||
texture: &self.texture,
|
||
mip_level: 0,
|
||
origin: wgpu::Origin3d::ZERO,
|
||
aspect: wgpu::TextureAspect::All,
|
||
},
|
||
wgpu::TexelCopyBufferInfo {
|
||
buffer: &self.readback,
|
||
layout: wgpu::TexelCopyBufferLayout {
|
||
offset: 0,
|
||
bytes_per_row: Some(self.padded_bpr),
|
||
rows_per_image: Some(self.height),
|
||
},
|
||
},
|
||
wgpu::Extent3d {
|
||
width: self.width,
|
||
height: self.height,
|
||
depth_or_array_layers: 1,
|
||
},
|
||
);
|
||
queue.submit(std::iter::once(encoder.finish()));
|
||
}
|
||
|
||
/// The mappable readback buffer (valid after [`copy_to_readback`]).
|
||
pub fn readback(&self) -> &wgpu::Buffer {
|
||
&self.readback
|
||
}
|
||
}
|
||
|
||
/// Convert a padded BGRA/RGBA readback into tightly-packed RGBA8 and encode it
|
||
/// as PNG bytes, reporting progress in `[0, 1]` via `on_progress` as rows are
|
||
/// streamed to the compressor (encoding is the slow, subdividable phase).
|
||
pub fn encode_png_with_progress(
|
||
padded: &[u8],
|
||
width: u32,
|
||
height: u32,
|
||
padded_bpr: u32,
|
||
swap_rb: bool,
|
||
mut on_progress: impl FnMut(f32),
|
||
) -> Vec<u8> {
|
||
use std::io::Write as _;
|
||
|
||
let row = (width * 4) as usize;
|
||
let mut out = Vec::new();
|
||
{
|
||
let mut encoder = png::Encoder::new(&mut out, width, height);
|
||
encoder.set_color(png::ColorType::Rgba);
|
||
encoder.set_depth(png::BitDepth::Eight);
|
||
let mut writer = encoder.write_header().expect("png header");
|
||
let mut stream = writer.stream_writer().expect("png stream");
|
||
let mut line = vec![0u8; row];
|
||
for y in 0..height as usize {
|
||
let src_off = y * padded_bpr as usize;
|
||
let src = &padded[src_off..src_off + row];
|
||
if swap_rb {
|
||
for x in 0..width as usize {
|
||
line[x * 4] = src[x * 4 + 2];
|
||
line[x * 4 + 1] = src[x * 4 + 1];
|
||
line[x * 4 + 2] = src[x * 4];
|
||
line[x * 4 + 3] = src[x * 4 + 3];
|
||
}
|
||
stream.write_all(&line).expect("png data");
|
||
} else {
|
||
stream.write_all(src).expect("png data");
|
||
}
|
||
if y % 64 == 0 {
|
||
on_progress(y as f32 / height as f32);
|
||
}
|
||
}
|
||
stream.finish().expect("png finish");
|
||
}
|
||
on_progress(1.0);
|
||
out
|
||
}
|
||
|
||
/// A per-frame paint callback. Carries this frame's uniforms plus a reference to
|
||
/// the current reference orbit (cheap `Arc` clone). The orbit is only re-uploaded
|
||
/// to the GPU when its `generation` changes, and the fractal is only re-rendered
|
||
/// into the cache when the uniforms, generation, or `size_px` change.
|
||
pub struct FractalCallback {
|
||
pub uniforms: Uniforms,
|
||
pub reference: Arc<Vec<[f32; 2]>>,
|
||
pub generation: u64,
|
||
/// Widget size in physical pixels — the cache texture resolution.
|
||
pub size_px: [u32; 2],
|
||
}
|
||
|
||
impl egui_wgpu::CallbackTrait for FractalCallback {
|
||
fn prepare(
|
||
&self,
|
||
device: &wgpu::Device,
|
||
queue: &wgpu::Queue,
|
||
_screen_descriptor: &egui_wgpu::ScreenDescriptor,
|
||
egui_encoder: &mut wgpu::CommandEncoder,
|
||
resources: &mut egui_wgpu::CallbackResources,
|
||
) -> Vec<wgpu::CommandBuffer> {
|
||
let Some(renderer) = resources.get_mut::<FractalRenderer>() else {
|
||
return Vec::new();
|
||
};
|
||
|
||
let width = self.size_px[0].max(1);
|
||
let height = self.size_px[1].max(1);
|
||
renderer.ensure_cache(device, width, height);
|
||
|
||
if renderer.uploaded_generation != self.generation && !self.reference.is_empty() {
|
||
let count = self.reference.len().min(MAX_REF_POINTS);
|
||
queue.write_buffer(
|
||
&renderer.ref_buffer,
|
||
0,
|
||
bytemuck::cast_slice(&self.reference[..count]),
|
||
);
|
||
renderer.uploaded_generation = self.generation;
|
||
}
|
||
|
||
// Re-render the cache only when what it depends on changed.
|
||
let dirty = renderer.rendered.as_ref().is_none_or(|r| {
|
||
r.generation != self.generation
|
||
|| r.width != width
|
||
|| r.height != height
|
||
|| bytemuck::bytes_of(&r.uniforms) != bytemuck::bytes_of(&self.uniforms)
|
||
});
|
||
if !dirty {
|
||
return Vec::new();
|
||
}
|
||
|
||
queue.write_buffer(
|
||
&renderer.uniform_buffer,
|
||
0,
|
||
bytemuck::bytes_of(&self.uniforms),
|
||
);
|
||
|
||
if let Some(cache) = &renderer.cache {
|
||
let mut pass = egui_encoder.begin_render_pass(&wgpu::RenderPassDescriptor {
|
||
label: Some("fractal cache pass"),
|
||
color_attachments: &[Some(wgpu::RenderPassColorAttachment {
|
||
view: &cache.view,
|
||
depth_slice: None,
|
||
resolve_target: None,
|
||
ops: wgpu::Operations {
|
||
load: wgpu::LoadOp::Clear(wgpu::Color::BLACK),
|
||
store: wgpu::StoreOp::Store,
|
||
},
|
||
})],
|
||
depth_stencil_attachment: None,
|
||
timestamp_writes: None,
|
||
occlusion_query_set: None,
|
||
multiview_mask: None,
|
||
});
|
||
pass.set_pipeline(&renderer.pipeline);
|
||
pass.set_bind_group(0, &renderer.bind_group, &[]);
|
||
pass.draw(0..3, 0..1);
|
||
}
|
||
|
||
renderer.rendered = Some(RenderedState {
|
||
uniforms: self.uniforms,
|
||
generation: self.generation,
|
||
width,
|
||
height,
|
||
});
|
||
Vec::new()
|
||
}
|
||
|
||
fn paint(
|
||
&self,
|
||
_info: egui::PaintCallbackInfo,
|
||
render_pass: &mut wgpu::RenderPass<'static>,
|
||
resources: &egui_wgpu::CallbackResources,
|
||
) {
|
||
if let Some(renderer) = resources.get::<FractalRenderer>()
|
||
&& let Some(cache) = &renderer.cache
|
||
{
|
||
render_pass.set_pipeline(&renderer.blit_pipeline);
|
||
render_pass.set_bind_group(0, &cache.blit_bind_group, &[]);
|
||
render_pass.draw(0..3, 0..1);
|
||
}
|
||
}
|
||
}
|