feat: add shadow coloring

Cargo.toml

@@ -26,7 +26,8 @@ web-sys = { version = "0.3.105", features = ["Window", "Location", "Url", "UrlSe
 # Release: optimize hard (fractal math is hot).
 [profile.release]
 opt-level = 3
-codegen-units = 1
+# codegen-units = 1
+debug = true
 
 # Dev: keep our own crate debuggable, but optimize dependencies (dashu, wgpu,
 # egui) so the explorer is actually interactive during development.

src/app.rs

@@ -10,6 +10,7 @@ use crate::fractal::{
 };
 #[cfg(target_arch = "wasm32")]
 use crate::fractal::{compute_reference, compute_set_reference};
+use crate::lights::Light;
 use crate::view::{
     Big, DEFAULT_HALF_HEIGHT, ViewState, big_from_decimal_str, big_from_f64, big_to_decimal_str,
     precision_for,
@@ -29,6 +30,8 @@ const INTERACT_DOWNSCALE: u32 = 2;
 const INTERACT_SETTLE: f64 = 0.12;
 /// Palette names; index maps to `palette_id` in the shader.
 const PALETTE_NAMES: &[&str] = &["Amber", "Rainbow", "Ember", "Lime", "Grayscale"];
+/// Shadow palette names; index maps to `palette_id` in the shader.
+const SHADOW_PALETTE_NAMES: &[&str] = &["Grayscale", "Red & Blue", "Custom lights"];
 /// Buddhabrot tonemap style names; index maps to `BuddhabrotUniforms::palette`.
 const BUDDHA_PALETTE_NAMES: &[&str] = &["Nebula", "Yellow", "Grayscale"];
 
@@ -121,7 +124,7 @@ const SET_PRESETS: [&[SetPreset]; FractalKind::Lambda as usize + 1] = [
             "-0.7436438870371587",
             "0.1318259042053",
             8.0e-8,
-            10000,
+            2000,
             None,
         ),
     ],
@@ -262,11 +265,17 @@ pub struct FractalApp {
     color_scale: f32,
     color_offset: f32,
     palette: u32,
+    shadow_palette: u32,
     /// Supersample each pixel 2×2 for smoother edges (costs ~4× fragment work).
     antialias: bool,
     /// Distance-estimation shading: darkens toward the set boundary using the
     /// orbit derivative, giving crisp filaments at deep zoom instead of speckle.
     de_coloring: bool,
+    // Use shadow coloring
+    shadow: bool,
+
+    /// List of enabled lights in the world
+    lights: Vec<Light>,
 
     /// Render as a Buddhabrot (Monte-Carlo orbit-density histogram) instead of
     /// the ordinary escape-time set. Plain f32 view — no deep zoom, no
@@ -401,8 +410,11 @@ impl FractalApp {
             color_scale: 0.15,
             color_offset: 0.0,
             palette: 0,
+            shadow_palette: 0,
             antialias: false,
             de_coloring: false,
+            shadow: false,
+            lights: vec![Light::default()],
             buddhabrot: false,
             buddha_r_cap: 50,
             buddha_g_cap: 500,
@@ -576,6 +588,7 @@ impl FractalApp {
             color_scale: self.color_scale,
             color_offset: self.color_offset,
             palette: self.palette,
+            shadow_palette: self.shadow_palette,
         }
     }
 
@@ -594,6 +607,8 @@ impl FractalApp {
         self.color_scale = s.color_scale;
         self.color_offset = s.color_offset;
         self.palette = (s.palette as usize).min(PALETTE_NAMES.len() - 1) as u32;
+        self.shadow_palette =
+            (s.shadow_palette as usize).min(SHADOW_PALETTE_NAMES.len() - 1) as u32;
         // The link carries an explicit iteration count; honor it rather than
         // letting the auto-scaler immediately overwrite it.
         self.auto_iterations = false;
@@ -802,14 +817,16 @@ impl FractalApp {
             bailout_sq: BAILOUT_SQ,
             is_julia: matches!(self.mode, FractalMode::Julia) as u32,
             palette_id: self.palette,
+            shadow_palette_id: self.shadow_palette,
             aa_level: if self.antialias { 2 } else { 1 },
             kind: self.kind as u32,
             power: self.power,
             dc_offset: self.dc_offset(),
             phoenix_p: [self.phoenix_p.0 as f32, self.phoenix_p.1 as f32],
             lambda_l: [self.lambda_l.0 as f32, self.lambda_l.1 as f32],
-            de_coloring: self.de_coloring as u32,
-            _pad: [0],
+            de_coloring: (self.de_coloring | self.shadow) as u32,
+            shadow: self.shadow as u32,
+            _pad: [0; _],
         }
     }
 
@@ -1354,6 +1371,8 @@ impl FractalApp {
                 .logarithmic(true),
         );
         ui.add(egui::Slider::new(&mut self.color_offset, 0.0..=1.0).text("color offset"));
+        ui.checkbox(&mut self.shadow, "Shadow");
+        if !self.shadow {
             egui::ComboBox::from_label("palette")
                 .selected_text(PALETTE_NAMES[self.palette as usize])
                 .show_ui(ui, |ui| {
@@ -1361,8 +1380,37 @@ impl FractalApp {
                         ui.selectable_value(&mut self.palette, i as u32, *name);
                     }
                 });
+        } else {
+            egui::ComboBox::from_label("palette")
+                .selected_text(SHADOW_PALETTE_NAMES[self.shadow_palette as usize])
+                .show_ui(ui, |ui| {
+                    for (i, name) in SHADOW_PALETTE_NAMES.iter().enumerate() {
+                        ui.selectable_value(&mut self.shadow_palette, i as u32, *name);
+                    }
+                });
+        }
+        if self.shadow && self.shadow_palette as usize == SHADOW_PALETTE_NAMES.len() - 1 {
+            ui.horizontal(|ui| {
+                ui.label("lights:");
+                if ui.button("+").clicked() {
+                    self.lights.push(Light::default());
+                }
+            });
+            egui::Grid::new("lights")
+                .striped(true)
+                .num_columns(1)
+                .show(ui, |ui| {
+                    self.lights.retain_mut(|light| {
+                        let delete = !light.widget(ui);
+                        ui.end_row();
+                        delete
+                    });
+                });
+        }
+        ui.separator();
         ui.checkbox(&mut self.antialias, "Antialiasing (2×2)")
             .on_hover_text("Supersample each pixel for smoother edges (~4× slower).");
+        if !self.shadow {
             ui.checkbox(&mut self.de_coloring, "Distance shading")
                 .on_hover_text(
                     "Shade by distance to the set boundary (from the orbit derivative) \
@@ -1370,8 +1418,10 @@ impl FractalApp {
                  (Mandelbrot/Multibrot/Phoenix), approximate for the abs-based kinds \
                  (Burning Ship/Tricorn/Celtic/Perpendicular/Buffalo).",
                 );
+        }
 
         ui.collapsing("Animation", |ui| {
+            if !self.shadow {
                 ui.checkbox(&mut self.anim.color, "Cycle colours")
                     .on_hover_text("Scroll the palette offset over time.");
                 if self.anim.color {
@@ -1381,6 +1431,7 @@ impl FractalApp {
                             .logarithmic(true),
                     );
                 }
+            }
 
             ui.checkbox(&mut self.anim.zoom, "Auto-zoom")
                 .on_hover_text("Continuously zoom toward the current center.");
@@ -1754,6 +1805,7 @@ impl FractalApp {
             rect,
             FractalCallback {
                 uniforms,
+                lights: self.lights.clone(),
                 reference: Arc::clone(&self.reference),
                 generation: self.generation,
                 size_px,

src/fractal/renderer.rs

@@ -13,6 +13,8 @@ use std::sync::Arc;
 
 use eframe::egui_wgpu::{self, wgpu};
 
+use crate::lights::{Light, MAX_LIGHT_COUNT};
+
 /// Maximum reference-orbit length (points) the storage buffer can hold. Also
 /// bounds the iteration count. 128k points * 8 bytes = 1 MiB.
 pub const MAX_REF_POINTS: usize = 1 << 17;
@@ -46,6 +48,8 @@ fn color_differs(a: &Uniforms, b: &Uniforms) -> bool {
     a.color_offset != b.color_offset
         || a.color_scale != b.color_scale
         || a.palette_id != b.palette_id
+        || a.shadow_palette_id != b.shadow_palette_id
+        || a.shadow != b.shadow
 }
 
 /// GPU-side view + coloring parameters. Layout must match `Uniforms` in the
@@ -64,12 +68,14 @@ pub struct Uniforms {
     /// 0 = Mandelbrot, 1 = Julia.
     pub is_julia: u32,
     pub palette_id: u32,
+    pub shadow_palette_id: u32,
     /// Supersampling factor per axis: 1 = off, 2 = 2×2 (4 samples).
     pub aa_level: u32,
     /// Iteration formula (`FractalKind::shader_id`).
     pub kind: u32,
     /// Exponent for the Multibrot kind.
     pub power: u32,
+    pub _pad: [u32; 1],
     /// Complex offset of the view center from the reference center, so a stale
     /// or reused reference (computed at a slightly different center) still maps
     /// correctly. Added to every pixel's per-pixel offset.
@@ -83,8 +89,8 @@ pub struct Uniforms {
     pub lambda_l: [f32; 2],
     /// 0 = escape-time coloring, 1 = distance-estimation shading.
     pub de_coloring: u32,
-    /// Padding to a 16-byte multiple (uniform buffer requirement).
-    pub _pad: [u32; 1],
+    // 0 = classic colors, 1 = shadows
+    pub shadow: u32,
 }
 
 /// Offscreen textures for the two-pass render, recreated whenever the widget's
@@ -128,6 +134,7 @@ pub struct FractalRenderer {
     bind_group_layout: wgpu::BindGroupLayout,
     uniform_buffer: wgpu::Buffer,
     ref_buffer: wgpu::Buffer,
+    lights_buffer: wgpu::Buffer,
     bind_group: wgpu::BindGroup,
     target_format: wgpu::TextureFormat,
     /// Generation of the reference orbit currently uploaded to `ref_buffer`.
@@ -170,6 +177,13 @@ impl FractalRenderer {
             mapped_at_creation: false,
         });
 
+        let lights_buffer = device.create_buffer(&wgpu::BufferDescriptor {
+            label: Some("lights parameters"),
+            size: (MAX_LIGHT_COUNT * std::mem::size_of::<Light>()) as u64,
+            usage: wgpu::BufferUsages::UNIFORM | wgpu::BufferUsages::COPY_DST,
+            mapped_at_creation: false,
+        });
+
         let bind_group_layout = device.create_bind_group_layout(&wgpu::BindGroupLayoutDescriptor {
             label: Some("fractal bind group layout"),
             entries: &[
@@ -301,6 +315,16 @@ impl FractalRenderer {
                         },
                         count: None,
                     },
+                    wgpu::BindGroupLayoutEntry {
+                        binding: 2,
+                        visibility: wgpu::ShaderStages::FRAGMENT,
+                        ty: wgpu::BindingType::Buffer {
+                            ty: wgpu::BufferBindingType::Uniform,
+                            has_dynamic_offset: false,
+                            min_binding_size: None,
+                        },
+                        count: None,
+                    },
                 ],
             });
         let colorize_pipeline_layout =
@@ -409,6 +433,7 @@ impl FractalRenderer {
             bind_group_layout,
             uniform_buffer,
             ref_buffer,
+            lights_buffer,
             bind_group,
             target_format,
             uploaded_generation: u64::MAX,
@@ -477,6 +502,10 @@ impl FractalRenderer {
                     binding: 1,
                     resource: wgpu::BindingResource::TextureView(&data_view),
                 },
+                wgpu::BindGroupEntry {
+                    binding: 2,
+                    resource: self.lights_buffer.as_entire_binding(),
+                },
             ],
         });
 
@@ -781,6 +810,7 @@ pub fn encode_png_with_progress(
 /// colourise pass (see `prepare`).
 pub struct FractalCallback {
     pub uniforms: Uniforms,
+    pub lights: Vec<Light>,
     pub reference: Arc<Vec<[f32; 2]>>,
     pub generation: u64,
     /// Widget size in physical pixels — the cache texture resolution.
@@ -827,7 +857,8 @@ impl egui_wgpu::CallbackTrait for FractalCallback {
         let color_dirty = iter_dirty
             || renderer.colored.as_ref().is_none_or(|c| {
                 c.width != width || c.height != height || color_differs(&c.uniforms, &self.uniforms)
-            });
+            })
+            || true;
 
         if !color_dirty {
             return Vec::new(); // cache still valid; paint() just blits it
@@ -839,6 +870,10 @@ impl egui_wgpu::CallbackTrait for FractalCallback {
             0,
             bytemuck::bytes_of(&self.uniforms),
         );
+        let mut bytes = [0; size_of::<Light>() * MAX_LIGHT_COUNT];
+        bytes[..self.lights.len() * size_of::<Light>()]
+            .copy_from_slice(bytemuck::cast_slice(&self.lights));
+        queue.write_buffer(&renderer.lights_buffer, 0, &bytes);
 
         if let Some(cache) = &renderer.cache {
             if iter_dirty {

src/fractal/share.rs

@@ -29,6 +29,8 @@ pub struct ShareState {
     pub color_offset: f32,
     /// Palette index (`palette_id` in the shader).
     pub palette: u32,
+    /// Shadow palette index (`shadow_palette_id` in the shader).
+    pub shadow_palette: u32,
 }
 
 impl ShareState {
@@ -110,6 +112,7 @@ impl ShareState {
             color_scale: map.get("cs").and_then(|s| s.parse().ok()).unwrap_or(0.02),
             color_offset: map.get("co").and_then(|s| s.parse().ok()).unwrap_or(0.0),
             palette: map.get("pal").and_then(|s| s.parse().ok()).unwrap_or(0),
+            shadow_palette: map.get("spal").and_then(|s| s.parse().ok()).unwrap_or(0),
         })
     }
 }
@@ -134,6 +137,7 @@ mod tests {
             color_scale: 0.02,
             color_offset: 0.25,
             palette: 3,
+            shadow_palette: 1,
         };
         let d = ShareState::decode(&s.encode()).unwrap();
         assert_eq!(d.julia, s.julia);
@@ -146,6 +150,7 @@ mod tests {
         assert_eq!(d.julia_c, s.julia_c);
         assert_eq!(d.phoenix_p, s.phoenix_p);
         assert_eq!(d.palette, s.palette);
+        assert_eq!(d.shadow_palette, s.shadow_palette);
     }
 
     #[test]

src/lights.rs

@@ -0,0 +1,55 @@
+use std::f32::consts::PI;
+
+use bytemuck::{Pod, Zeroable};
+use egui::{Color32, Ui};
+
+/// Maximum number of simultaneous lights.
+pub const MAX_LIGHT_COUNT: usize = 16;
+
+#[derive(Clone, Copy, PartialEq, Zeroable, Pod)]
+#[repr(C)]
+pub struct Light {
+    pub azimuth: f32,
+    pub altitude: f32,
+    pub color: Color32,
+    pub _pad: u32,
+}
+
+impl Default for Light {
+    fn default() -> Self {
+        Self {
+            azimuth: PI / 4.,
+            altitude: PI / 4.,
+            color: Color32::WHITE,
+            _pad: 0,
+        }
+    }
+}
+
+impl Light {
+    pub fn widget(&mut self, ui: &mut Ui) -> bool {
+        let formater = |v, _| format!("{}°", ((v as f32 * 180. / PI) as u32));
+        ui.horizontal(|ui| {
+            let del = ui.button("-").clicked();
+            ui.label("color:");
+            ui.color_edit_button_srgba(&mut self.color);
+            ui.label("θ:");
+            ui.add(
+                egui::DragValue::new(&mut self.azimuth)
+                    .range(0.0..=PI * 2.)
+                    .custom_formatter(formater)
+                    .speed(0.02),
+            );
+            ui.label("φ:");
+            ui.add(
+                egui::DragValue::new(&mut self.altitude)
+                    .range(0.0..=PI / 2.)
+                    .custom_formatter(formater)
+                    .speed(0.02),
+            );
+
+            del
+        })
+        .inner
+    }
+}

src/main.rs

@@ -9,6 +9,7 @@
 // and calls the wasm `main`, which boots eframe onto the page's <canvas>.
 
 mod app;
+mod lights;
 mod fractal;
 mod view;
 

src/shaders/colorize.wgsl

@@ -20,32 +20,43 @@ struct Uniforms {
     bailout_sq: f32,
     is_julia: u32,
     palette_id: u32,
+    shadow_palette_id: u32,
     aa_level: u32,
     kind: u32,
     power: u32,
     dc_offset: vec2<f32>,
     phoenix_p: vec2<f32>,
+    lambda_l: vec2<f32>,
     de_coloring: u32,
+    shadow: u32,
+};
+
+struct Light {
+    azimuth: f32,
+    altitude: f32,
+    color: u32,
+    _pad: u32
 };
 
 @group(0) @binding(0) var<uniform> u: Uniforms;
 @group(0) @binding(1) var data_tex: texture_2d<f32>;
+@group(0) @binding(2) var<uniform> lights: array<Light, 16>;
 
 // Smooth cyclic palettes (Inigo Quilez cosine palettes). Must match the palette
 // in mandelbrot.wgsl.
 fn palette(id: u32, t: f32) -> vec3<f32> {
-    if (id == 4u) {
+    if id == 4u {
         return vec3<f32>(t, t, t); // grayscale
     }
     let a = vec3<f32>(0.5, 0.5, 0.5);
     let b = vec3<f32>(0.5, 0.5, 0.5);
     var c = vec3<f32>(1.0, 1.0, 1.0);
     var d = vec3<f32>(0.00, 0.10, 0.20); // 0: amber / blue
-    if (id == 1u) {
+    if id == 1u {
         d = vec3<f32>(0.00, 0.33, 0.67); // rainbow
-    } else if (id == 2u) {
+    } else if id == 2u {
         d = vec3<f32>(0.30, 0.20, 0.20); // warm ember
-    } else if (id == 3u) {
+    } else if id == 3u {
         c = vec3<f32>(1.0, 1.0, 0.5);
         d = vec3<f32>(0.80, 0.90, 0.30); // lime / magenta
     }
@@ -62,8 +73,86 @@ fn vs_main(@builtin(vertex_index) idx: u32) -> @builtin(position) vec4<f32> {
     return vec4<f32>(verts[idx], 0.0, 1.0);
 }
 
+fn load(x: i32, y: i32) -> vec3<f32> {
+    let dist = textureLoad(data_tex, vec2<i32>(x, y), 0).g;
+    return vec3<f32>(f32(x), f32(y), dist);
+}
+
+fn compute_light(normal: vec3<f32>, light: vec3<f32>) -> vec3<f32> {
+    return vec3<f32>(max(0., dot(normal, normalize(light))));
+}
+
+fn uncharted2tonemap(x: vec3<f32>) -> vec3<f32> {
+    let A = 0.15; // Shoulder strength
+    let B = 0.50; // Linear strength
+    let C = 0.10; // Linear angle
+    let D = 0.20; // Toe strength
+    let E = 0.02; // Toe numerator / shoarder angle/etc.
+    let F = 0.30; // Toe denominator
+
+    return ((x * (A * x + C * B) + D * E) / (x * (A * x + B) + D * F)) - E / F;
+}
+
+fn filmic(color: vec3<f32>, white_point: f32) -> vec3<f32> {
+    let exposure_bias = 2.0;
+    let curr = uncharted2tonemap(color * exposure_bias);
+    
+    // Valeur blanche maximale de référence
+    let white_scale = vec3(1.0) / uncharted2tonemap(vec3(white_point));
+    return curr * white_scale;
+}
+
+fn s(color: vec3<f32>, k: f32, c: f32) -> vec3<f32> {
+    return 1. / (1. + exp(-k * (color - c)));
+}
+
+fn contrast(color: vec3<f32>, k: f32, c: f32) -> vec3<f32> {
+    let color_c = s(color, k, c);
+
+    return (color_c - s(vec3<f32>(0), k, c)) / (s(vec3<f32>(1), k, c) - s(vec3<f32>(0), k, c));
+}
+
 @fragment
 fn fs_main(@builtin(position) pos: vec4<f32>) -> @location(0) vec4<f32> {
+    if u.shadow != 0u {
+        if textureLoad(data_tex, vec2<i32>(i32(pos.x), i32(pos.y)), 0).b != 0. {
+            return vec4<f32>(0.1, 0.1, 0.1, 1.0);
+        } else {
+            let d = array<vec3<f32>, 3>(load(i32(pos.x), i32(pos.y)), load(i32(pos.x + 1), i32(pos.y)), load(i32(pos.x), i32(pos.y + 1)));
+
+            let normal = normalize(cross(d[1] - d[0], d[2] - d[0]));
+
+            var color: vec3<f32>;
+            if u.shadow_palette_id == 0u {
+                color = compute_light(normal,vec3<f32>(.5, .5, .5)) + vec3<f32>(0.58, 0.85, 1.) * 0.2;
+
+                color = filmic(color, 2.5);
+                color = contrast(color, 4., 0.67);
+            } else if u.shadow_palette_id == 1u {
+                color = compute_light(normal, vec3<f32>(0., .5, .5)) * vec3<f32>(1., 0.5, 0.5) + compute_light(normal, vec3<f32>(0.5, 0., .5)) * vec3<f32>(0.5, 1., 1.);
+
+                color = filmic(color, 4.2);
+            } else {
+                color = vec3<f32>(0);
+                var light_count = 0;
+                for (var i = 0u ; i < 16; i++) {
+                    let light_color = unpack4x8unorm(lights[i].color);
+                    if any(light_color != vec4<f32>(0)) {
+                        light_count       += 1;
+                    }
+
+                    color       += compute_light(normal, vec3<f32>(
+                        cos(lights[i].azimuth) * cos(lights[i].altitude),
+                        sin(lights[i].azimuth) * cos(lights[i].altitude),
+                        sin(lights[i].altitude))) * light_color.xyz * light_color.a;
+                }
+
+                color = filmic(color, 1. + f32(light_count));
+            }
+
+            return vec4<f32>(color, 1.0);
+        }
+    } else {
         let d = textureLoad(data_tex, vec2<i32>(i32(pos.x), i32(pos.y)), 0);
         let ci = d.r;
         let de = d.g;
@@ -76,3 +165,4 @@ fn fs_main(@builtin(position) pos: vec4<f32>) -> @location(0) vec4<f32> {
         col = col * (1.0 - interior_frac);
         return vec4<f32>(col, 1.0);
     }
+}

src/shaders/mandelbrot.wgsl

@@ -21,6 +21,7 @@ struct Uniforms {
     bailout_sq: f32,
     is_julia: u32,
     palette_id: u32,
+    shadow_palette_id: u32,
     aa_level: u32,
     // Iteration formula (see the KIND_* constants below).
     kind: u32,
@@ -35,6 +36,8 @@ struct Uniforms {
     lambda_l: vec2<f32>,
     // 0 = escape-time coloring, 1 = distance-estimation shading.
     de_coloring: u32,
+    // 0 = classic colors, 1 = shadows
+    shadow: u32,
 };
 
 const KIND_MANDELBROT: u32 = 0u;
@@ -326,7 +329,11 @@ fn iterate_sample(offset: vec2<f32>, px: f32) -> Sample {
         let zmag = sqrt(max(z2, 1.0));
         let dzmag = sqrt(max(dot(dz, dz), 1e-20));
         let d = zmag * log(zmag) / dzmag;
-        de = clamp(d / max(px, 1e-30), 0.0, 1.0);
+        var max_de = 1.;
+        if u.shadow != 0u {
+            max_de = 1000.;
+        }
+        de = clamp(d / max(px, 1e-30), 0.0, max_de);
     }
     return Sample(ci, de, true);
 }