xfy
e2e2469971
Restructures the disk block in the main loop: - Off tier: flat disk_color_flat single midplane sample (old behavior). - Volumetric tiers: (A) in-slab per-step sampling accumulates emission × arc length, reusing the RK45 adaptive step density; (B) midplane edge- capture weights one at-plane sample by slab depth along the ray. Removes the Task-5 disk_color shim. physics.rs untouched; cargo test green.
610 lines
24 KiB
WebGPU Shading Language
610 lines
24 KiB
WebGPU Shading Language
// All shader logic is inlined into this single file.
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//
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// HISTORY: the shader used to be split across several naga_oil modules
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// (ray_gen, geodesic, stars, disk, planets, grid, skybox) that each
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// `#define_import_path singularity::...` and were pulled into this file via
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// `#import singularity::...`. That compiled without error, but calling ANY
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// imported function at runtime produced no fragment output — the fullscreen
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// quad silently drew nothing and only the camera clear color (grey) showed.
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// (Local functions worked; only cross-module imports broke.) Rather than chase
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// the naga_oil composition bug, every function is inlined here. The standalone
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// module files still exist on disk but are no longer imported.
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#import bevy_sprite::mesh2d_vertex_output::VertexOutput
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struct BlackHoleUniforms {
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eye: vec4<f32>,
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forward: vec4<f32>,
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right: vec4<f32>,
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up: vec4<f32>,
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resolution: vec2<f32>,
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time: f32,
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_pad3: f32,
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rs: f32,
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disk_inner: f32,
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disk_outer: f32,
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disk_tilt: f32,
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disk_brightness: f32,
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disk_rotation_speed: f32,
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doppler_strength: f32,
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star_intensity: f32,
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skybox_intensity: f32,
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grid_density: f32,
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doppler_enabled: u32,
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grid_enabled: u32,
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planet_count: u32,
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steps: u32,
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spin: f32,
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star_aa: u32,
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bloom_threshold: f32,
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bloom_strength: f32,
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exposure: f32,
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_pad5: f32,
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disk_half_thickness: f32,
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filament_freq: f32,
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filament_sharpness: f32,
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density_freq: f32,
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density_strength: f32,
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arm_count: f32,
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arm_tightness: f32,
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arm_strength: f32,
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disk_quality: u32,
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};
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@group(#{MATERIAL_BIND_GROUP}) @binding(0) var<uniform> uniforms: BlackHoleUniforms;
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// ---------- planets storage (binding 3) ----------
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struct SphereData {
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center: vec4<f32>, // xyz = center (world space), w = radius
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color: vec4<f32>, // xyz = color, w = emissive flag
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};
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@group(#{MATERIAL_BIND_GROUP}) @binding(3) var<storage, read> planets: array<SphereData>;
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// ---------- optional cubemap skybox (bindings 1 & 2) ----------
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@group(#{MATERIAL_BIND_GROUP}) @binding(1) var skybox: texture_cube<f32>;
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@group(#{MATERIAL_BIND_GROUP}) @binding(2) var skybox_sampler: sampler;
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// ====================== inlined helpers ======================
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// Rotate a vector around the X axis by angle a.
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fn rot_x(v: vec3<f32>, a: f32) -> vec3<f32> {
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let c = cos(a);
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let s = sin(a);
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return vec3<f32>(v.x, c * v.y - s * v.z, s * v.y + c * v.z);
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}
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// --- ray_gen ---
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// `fov` is packed into the `.w` of `up` (Rust lays out `up: Vec3` + `fov: f32`
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// as one vec4 block).
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fn ray_direction(uv: vec2<f32>) -> vec3<f32> {
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let tan_half_fov = tan(uniforms.up.w * 0.5);
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let dir =
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normalize(uniforms.forward.xyz)
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+ uniforms.right.xyz * (uv.x * tan_half_fov)
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+ uniforms.up.xyz * (uv.y * tan_half_fov);
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return normalize(dir);
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}
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// --- stars ---
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fn hash13(p: vec3<f32>) -> f32 {
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var q = vec3<f32>(dot(p, vec3<f32>(127.1, 311.7, 74.7)),
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dot(p, vec3<f32>(269.5, 183.3, 246.1)),
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dot(p, vec3<f32>(113.5, 271.9, 124.6)));
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let h = fract(sin(q) * 43758.5453);
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return h.x;
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}
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fn star_color(dir: vec3<f32>, intensity: f32) -> vec3<f32> {
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// The unit-sphere direction is hashed into a 3D cell grid. A pixel's ray
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// usually sits near a cell boundary, so evaluating only the home cell clips
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// any star whose center lies in a neighbor — that clip is what made stars
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// look square even with the Gaussian AA path: the hash changes at the cell
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// edge, so the falloff could never reach zero and the visible shape was
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// just the cell's bounding box. Scan the 3×3×3 neighborhood so each star's
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// radial falloff extends across the whole cell it lives in.
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let scale = 80.0;
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let p = dir * scale;
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let base = floor(p);
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let threshold = 0.985;
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// Brightest contributor wins: `best` = (brightness, r, g, b).
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var best = vec4<f32>(0.0);
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for (var dz: i32 = -1; dz <= 1; dz = dz + 1) {
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for (var dy: i32 = -1; dy <= 1; dy = dy + 1) {
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for (var dx: i32 = -1; dx <= 1; dx = dx + 1) {
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let cell = base + vec3<f32>(f32(dx), f32(dy), f32(dz));
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let h = hash13(cell);
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if (h <= threshold) { continue; }
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let b = (h - threshold) / (1.0 - threshold);
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let center = cell + vec3<f32>(0.5);
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let dist = length(p - center); // Euclidean → round, never square
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let col = mix(vec3<f32>(0.6, 0.7, 1.0), vec3<f32>(1.0, 0.9, 0.7), b);
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// Both paths share the same brightness-driven radius and the
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// same gain, so toggling AA only softens the edge — it does not
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// change peak brightness or visible count. Before, the AA path
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// used a larger radius (up to 0.65 vs 0.5), a heavier gain
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// (4.0 vs 3.0), and a slow-decaying Gaussian whose long tail
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// lifted many dim stars above the visibility floor — that's
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// what made AA look like "bigger and more" stars.
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let radius = 0.25 + b * 0.4;
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let falloff = select(
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smoothstep(radius, 0.0, dist), // hard edge
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exp(-4.6 * dist * dist / (radius * radius)), // soft edge
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uniforms.star_aa != 0u);
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let bright = b * falloff;
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if (bright > best.x) {
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best = vec4<f32>(bright, col.r, col.g, col.b);
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}
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}
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}
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}
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return best.yzw * best.x * 3.0 * intensity;
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}
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// --- skybox ---
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fn skybox_color(dir: vec3<f32>) -> vec3<f32> {
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return textureSample(skybox, skybox_sampler, dir).rgb;
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}
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// --- geodesic ---
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struct Deriv {
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dpos: vec3<f32>,
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ddir: vec3<f32>,
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}
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fn deriv(pos: vec3<f32>, dir: vec3<f32>) -> Deriv {
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let r = length(pos);
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let rs = uniforms.rs;
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// Kerr spin. χ ∈ [0,1]; a = χ·M, M = Rs/2 = 0.5 (Rs=1).
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let chi = uniforms.spin;
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let m = 0.5;
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let a = chi * m;
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// Schwarzschild radial bending (identical to Phase 1 at χ=0).
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let h = cross(pos, dir);
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let h2 = dot(h, h);
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let r5 = max(r * r * r * r * r, 1e-6);
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let radial = -1.5 * rs * h2 / r5 * pos;
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// Frame-dragging (Lense-Thirring leading term). Spin axis = +Y.
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let spin_axis = vec3<f32>(0.0, 1.0, 0.0);
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let r3 = max(r * r * r, 1e-6);
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let drag = 2.0 * m * a / r3 * cross(spin_axis, dir);
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let accel = radial + drag;
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return Deriv(dir, accel);
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}
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// --- disk ---
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fn disk_hit(prev: vec3<f32>, cur: vec3<f32>) -> bool {
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let y0 = prev.y;
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let y1 = cur.y;
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if (y0 * y1 > 0.0) {
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return false;
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}
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let t = y0 / (y0 - y1);
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let cross = mix(prev, cur, vec3<f32>(t));
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let r = length(vec2<f32>(cross.x, cross.z));
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return r >= uniforms.disk_inner && r <= uniforms.disk_outer;
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}
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// --- disk noise (domain-warped FBM) ---
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fn hash33(p: vec3<f32>) -> vec3<f32> {
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let q = vec3<f32>(
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dot(p, vec3<f32>(127.1, 311.7, 74.7)),
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dot(p, vec3<f32>(269.5, 183.3, 246.1)),
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dot(p, vec3<f32>(113.5, 271.9, 124.6)),
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);
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return fract(sin(q) * 43758.5453);
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}
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fn value_noise3(p: vec3<f32>) -> f32 {
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let i = floor(p);
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let f = fract(p);
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let u = f * f * (3.0 - 2.0 * f);
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let n000 = hash33(i + vec3<f32>(0.0, 0.0, 0.0)).x;
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let n100 = hash33(i + vec3<f32>(1.0, 0.0, 0.0)).x;
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let n010 = hash33(i + vec3<f32>(0.0, 1.0, 0.0)).x;
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let n110 = hash33(i + vec3<f32>(1.0, 1.0, 0.0)).x;
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let n001 = hash33(i + vec3<f32>(0.0, 0.0, 1.0)).x;
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let n101 = hash33(i + vec3<f32>(1.0, 0.0, 1.0)).x;
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let n011 = hash33(i + vec3<f32>(0.0, 1.0, 1.0)).x;
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let n111 = hash33(i + vec3<f32>(1.0, 1.0, 1.0)).x;
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let nx00 = mix(n000, n100, u.x);
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let nx10 = mix(n010, n110, u.x);
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let nx01 = mix(n001, n101, u.x);
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let nx11 = mix(n011, n111, u.x);
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let nxy0 = mix(nx00, nx10, u.y);
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let nxy1 = mix(nx01, nx11, u.y);
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return mix(nxy0, nxy1, u.z);
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}
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fn fbm3(p: vec3<f32>, octaves: u32) -> f32 {
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var sum = 0.0;
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var amp = 0.5;
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var freq = 1.0;
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for (var i: u32 = 0u; i < octaves; i = i + 1u) {
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sum = sum + amp * value_noise3(p * freq);
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freq = freq * 2.0;
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amp = amp * 0.5;
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}
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return sum;
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}
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// Ridged multifractal noise: 1 - |2n-1| turns value-noise gradients into
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// sharp ridges (peak where n=0.5, zero at n=0 and n=1). Raising to
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// `sharpness` thins the ridges into filaments. MAX_OCTAVES-with-break is
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// the conservative WebGPU form for a runtime-chosen octave count.
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fn ridged_fbm(p: vec3<f32>, octaves: u32, sharpness: f32) -> f32 {
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const MAX_OCTAVES = 6u;
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var sum = 0.0;
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var amp = 0.5;
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var freq = 1.0;
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for (var i: u32 = 0u; i < MAX_OCTAVES; i = i + 1u) {
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if (i >= octaves) { break; }
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let n = value_noise3(p * freq);
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let ridge = 1.0 - abs(2.0 * n - 1.0);
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sum = sum + amp * pow(ridge, sharpness);
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freq = freq * 2.0;
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amp = amp * 0.5;
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}
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return sum;
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}
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fn disk_noise(pos: vec3<f32>, t: f32) -> f32 {
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let warp = fbm3(pos * 0.8 + vec3<f32>(0.0, 0.0, t * 0.1), 3u);
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let n = fbm3(pos * 2.0 + warp * 1.5 + vec3<f32>(0.0, 0.0, t * 0.3), 4u);
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return n;
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}
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// Result of a disk color query: emitted radiance + opacity contribution.
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// Both the volumetric and flat paths return this struct so the main loop
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// can treat them uniformly.
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struct DiskSample {
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color: vec3<f32>,
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density: f32,
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}
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// Radial temperature gradient: white-hot inner → deep-orange outer.
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fn temperature_color(t: f32) -> vec3<f32> {
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return mix(vec3<f32>(1.0, 0.95, 0.85), vec3<f32>(1.0, 0.45, 0.12), clamp(t, 0.0, 1.0));
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}
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// Radial brightness falloff (∝ 1/r² from the inner edge).
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fn radial_falloff(r: f32, inner: f32) -> f32 {
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return 1.0 / pow(r / inner, 2.0);
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}
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// Cylindrical radius in the disk plane.
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fn r_of(pos: vec3<f32>) -> f32 {
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return length(vec2<f32>(pos.x, pos.z));
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}
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// Relativistic Doppler beaming. `dir` is the ray direction (disk-local).
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fn apply_doppler(col: vec3<f32>, pos: vec3<f32>, dir: vec3<f32>) -> vec3<f32> {
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let phi = atan2(pos.z, pos.x);
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let v_orbital = sqrt(uniforms.rs / (2.0 * r_of(pos)));
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let tangent = normalize(vec3<f32>(-sin(phi), 0.0, cos(phi)));
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let vdotn = dot(tangent * v_orbital, -dir);
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let gamma = 1.0 / sqrt(max(1.0 - v_orbital * v_orbital, 1e-4));
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if (uniforms.doppler_enabled == 0u) {
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return col;
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}
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let delta = 1.0 / (gamma * (1.0 - vdotn));
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let doppler = pow(delta, 3.0) * uniforms.doppler_strength;
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return col * doppler;
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}
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// Off-tier fallback: zero-thickness disk, single sample, fixed alpha.
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// Preserves the exact pre-volumetric appearance. Returns DiskSample so the
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// main loop dispatches both paths uniformly.
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fn disk_color_flat(pos: vec3<f32>, dir: vec3<f32>) -> DiskSample {
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let r = r_of(pos);
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let rot = uniforms.time * uniforms.disk_rotation_speed / pow(r, 1.5);
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// Domain-warped FBM for feathered/smoky gas texture. The Keplerian shear
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// (rot ∝ 1/r^1.5) is folded into the noise flow term so inner radii flow
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// faster than outer — correct differential rotation.
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let noise = disk_noise(vec3<f32>(pos.x * 0.3, pos.z * 0.3, rot), uniforms.time);
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let t = (r - uniforms.disk_inner) / (uniforms.disk_outer - uniforms.disk_inner);
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let tcol = temperature_color(t);
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let falloff = radial_falloff(r, uniforms.disk_inner);
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var col = tcol * (0.6 + 0.4 * noise) * falloff * uniforms.disk_brightness;
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col = apply_doppler(col, pos, dir);
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return DiskSample(vec3<f32>(col), 0.85);
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}
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// Volumetric disk color: ridged filaments drive brightness, a smoothstep-
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// gated FBM drives density clumping, and a logarithmic-spiral term (riding
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// the Keplerian shear `rot`) drives large-scale arm structure. The three
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// signals multiply — density says where matter is, filaments say how bright,
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// arms say how it's distributed.
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fn disk_color_volumetric(pos: vec3<f32>, dir: vec3<f32>) -> DiskSample {
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let r = r_of(pos);
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let rot = uniforms.time * uniforms.disk_rotation_speed / pow(r, 1.5);
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let flow = vec3<f32>(0.0, 0.0, rot);
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// Octave triplet from the quality tier.
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let q = uniforms.disk_quality;
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var filament_octaves = 5u; var density_octaves = 4u; var warp_octaves = 3u;
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if (q == 1u) { filament_octaves = 3u; density_octaves = 2u; warp_octaves = 2u; }
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else if (q == 2u) { filament_octaves = 4u; density_octaves = 3u; warp_octaves = 3u; }
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// q == 3u keeps the High defaults above; q == 0u is never passed here.
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// Domain warp: distorts sample coords so filaments curve and bend.
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let warp = fbm3(pos * 0.8 + flow * 0.1, warp_octaves);
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// Layer 1: ridged bright filaments.
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let filament = ridged_fbm(pos * uniforms.filament_freq + warp * 1.5 + flow * 0.3,
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filament_octaves, uniforms.filament_sharpness);
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// Layer 2: density clumping (smoothstep makes a definite gas/void boundary).
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let density_noise = fbm3(pos * uniforms.density_freq + warp, density_octaves);
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let base_density = smoothstep(0.3, 0.7, density_noise) * uniforms.density_strength;
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// Layer 3: logarithmic-spiral arm modulation, advected by Keplerian shear.
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let phi = atan2(pos.z, pos.x);
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let arm_phase = phi * uniforms.arm_count + log(r) * uniforms.arm_tightness - rot;
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let arm = 0.5 + 0.5 * cos(arm_phase);
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let arm_mod = mix(1.0, pow(arm, 2.0), uniforms.arm_strength);
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let total_density = base_density * arm_mod;
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let brightness = filament;
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let t = (r - uniforms.disk_inner) / (uniforms.disk_outer - uniforms.disk_inner);
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let tcol = temperature_color(t);
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let falloff = radial_falloff(r, uniforms.disk_inner);
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var col = tcol * brightness * falloff * uniforms.disk_brightness;
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col = apply_doppler(col, pos, dir);
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return DiskSample(vec3<f32>(col), total_density);
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}
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// --- planets ---
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// `prev`/`cur` are in DISK-LOCAL space; planet centers are world space, so we
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// rotate each center into disk-local space here.
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fn planet_hit(prev: vec3<f32>, cur: vec3<f32>, dir: vec3<f32>) -> vec4<f32> {
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var nearest_t = 1e9;
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var nearest_col = vec3<f32>(0.0);
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var found = false;
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for (var i: u32 = 0u; i < uniforms.planet_count; i = i + 1u) {
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let s = planets[i];
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let center = rot_x(s.center.xyz, -uniforms.disk_tilt);
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let radius = s.center.w;
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let seg = cur - prev;
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let oc = prev - center;
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let a = dot(seg, seg);
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let b = 2.0 * dot(oc, seg);
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let c = dot(oc, oc) - radius * radius;
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let disc = b * b - 4.0 * a * c;
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if (disc < 0.0) { continue; }
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let sq = sqrt(disc);
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var t = (-b - sq) / (2.0 * a);
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if (t < 0.0) { t = (-b + sq) / (2.0 * a); }
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if (t >= 0.0 && t <= 1.0 && t < nearest_t) {
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nearest_t = t;
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let hit_pos = prev + seg * t;
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let n = normalize(hit_pos - center);
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let light_dir = normalize(vec3<f32>(0.5, 0.8, 0.3));
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let ndl = max(dot(n, light_dir), 0.0);
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var col = s.color.xyz * (0.2 + 0.8 * ndl);
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if (s.color.w > 0.5) { col = s.color.xyz; }
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nearest_col = col;
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found = true;
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}
|
||
}
|
||
if (found) {
|
||
return vec4<f32>(nearest_col, 0.95);
|
||
}
|
||
return vec4<f32>(0.0, 0.0, 0.0, 0.0);
|
||
}
|
||
|
||
// --- grid (Flamm's paraboloid) ---
|
||
fn flamm_depth(r: f32) -> f32 {
|
||
if (r <= uniforms.rs) { return 0.0; }
|
||
return -2.0 * sqrt(uniforms.rs * (r - uniforms.rs));
|
||
}
|
||
|
||
fn grid_hit(prev: vec3<f32>, cur: vec3<f32>) -> vec3<f32> {
|
||
let r0 = length(vec2<f32>(prev.x, prev.z));
|
||
let r1 = length(vec2<f32>(cur.x, cur.z));
|
||
let z0_surf = flamm_depth(r0);
|
||
let z1_surf = flamm_depth(r1);
|
||
if ((prev.y - z0_surf) * (cur.y - z1_surf) > 0.0) {
|
||
return vec3<f32>(0.0);
|
||
}
|
||
var hit = vec3<f32>(0.0);
|
||
var found = false;
|
||
for (var s: i32 = 0; s < 8; s = s + 1) {
|
||
let f = f32(s + 1) / 8.0;
|
||
let p = mix(prev, cur, vec3<f32>(f));
|
||
let r = length(vec2<f32>(p.x, p.z));
|
||
let surf = flamm_depth(r);
|
||
if (abs(p.y - surf) < 0.3) {
|
||
hit = p;
|
||
found = true;
|
||
break;
|
||
}
|
||
}
|
||
if (!found) { return vec3<f32>(0.0); }
|
||
|
||
let r = length(vec2<f32>(hit.x, hit.z));
|
||
let phi = atan2(hit.z, hit.x);
|
||
let ring = smoothstep(0.06, 0.0, abs(fract(r * uniforms.grid_density * 0.5) - 0.5));
|
||
let spoke = smoothstep(0.04, 0.0, abs(fract(phi * 6.0 / 6.283185) - 0.5));
|
||
let grid = max(ring, spoke);
|
||
let fade = smoothstep(-15.0, -1.0, hit.y);
|
||
let col = vec3<f32>(0.15, 0.3, 0.6) * grid * fade;
|
||
return col * 0.5;
|
||
}
|
||
|
||
// One Dormand-Prince RK45 step. Returns the 5th-order solution and the
|
||
// error estimate (y5 - y4) as a vec3 (position error; direction error is
|
||
// folded in via normalize so we only need position error for step control).
|
||
struct RkStep {
|
||
pos: vec3<f32>,
|
||
dir: vec3<f32>,
|
||
err: f32,
|
||
};
|
||
|
||
fn rk45_step(pos: vec3<f32>, dir: vec3<f32>, dt: f32) -> RkStep {
|
||
// Butcher tableau (Dormand-Prince), 6 stages. Each deriv() returns Deriv{dpos, ddir}.
|
||
let k1 = deriv(pos, dir);
|
||
let p2 = pos + k1.dpos * dt * 0.2;
|
||
let d2 = normalize(dir + k1.ddir * dt * 0.2);
|
||
let k2 = deriv(p2, d2);
|
||
let p3 = pos + (k1.dpos * 0.075 + k2.dpos * 0.225) * dt;
|
||
let d3 = normalize(dir + (k1.ddir * 0.075 + k2.ddir * 0.225) * dt);
|
||
let k3 = deriv(p3, d3);
|
||
let p4 = pos + (k1.dpos * 0.3 + k2.dpos * -0.9 + k3.dpos * 1.2) * dt;
|
||
let d4 = normalize(dir + (k1.ddir * 0.3 + k2.ddir * -0.9 + k3.ddir * 1.2) * dt);
|
||
let k4 = deriv(p4, d4);
|
||
let p5 = pos + (k1.dpos * -11.0/54.0 + k2.dpos * 2.5 + k3.dpos * -70.0/27.0 + k4.dpos * 35.0/27.0) * dt;
|
||
let d5 = normalize(dir + (k1.ddir * -11.0/54.0 + k2.ddir * 2.5 + k3.ddir * -70.0/27.0 + k4.ddir * 35.0/27.0) * dt);
|
||
let k5 = deriv(p5, d5);
|
||
let p6 = pos + (k1.dpos * 1631.0/55296.0 + k2.dpos * 175.0/512.0 + k3.dpos * 575.0/13824.0 + k4.dpos * 44275.0/110592.0 + k5.dpos * 253.0/4096.0) * dt;
|
||
let d6 = normalize(dir + (k1.ddir * 1631.0/55296.0 + k2.ddir * 175.0/512.0 + k3.ddir * 575.0/13824.0 + k4.ddir * 44275.0/110592.0 + k5.ddir * 253.0/4096.0) * dt);
|
||
let k6 = deriv(p6, d6);
|
||
// 5th-order solution (used to advance).
|
||
let new_pos = pos + (k1.dpos * 37.0/378.0 + k3.dpos * 250.0/621.0 + k4.dpos * 125.0/594.0 + k5.dpos * 512.0/1771.0 + k6.dpos * 0.0) * dt;
|
||
let new_dir = normalize(dir + (k1.ddir * 37.0/378.0 + k3.ddir * 250.0/621.0 + k4.ddir * 125.0/594.0 + k5.ddir * 512.0/1771.0 + k6.ddir * 0.0) * dt);
|
||
// 4th-order solution (for error estimate).
|
||
let pos4 = pos + (k1.dpos * 2825.0/27648.0 + k3.dpos * 18575.0/48384.0 + k4.dpos * 13525.0/55296.0 + k5.dpos * 277.0/14336.0 + k6.dpos * 0.25) * dt;
|
||
let err = length(new_pos - pos4);
|
||
return RkStep(new_pos, new_dir, err);
|
||
}
|
||
|
||
// ====================== main ======================
|
||
@fragment
|
||
fn fragment(in: VertexOutput) -> @location(0) vec4<f32> {
|
||
let aspect = uniforms.resolution.x / uniforms.resolution.y;
|
||
var uv = (in.uv * 2.0 - 1.0);
|
||
uv.x *= aspect;
|
||
let dir = ray_direction(uv);
|
||
|
||
// Work in disk-local space: rotate eye + dir by -disk_tilt around X so the
|
||
// disk lies on y=0. (disk_hit/disk_color assume disk-local coords.)
|
||
|
||
// Total path length to integrate: enough to go from the camera, past the
|
||
// hole, and far enough beyond to count as escaped.
|
||
let eye_dist = length(uniforms.eye.xyz);
|
||
let escape_r = max(eye_dist * 2.0, 100.0);
|
||
let total_path = eye_dist + escape_r;
|
||
// Adaptive RK45 constants.
|
||
let steps_max = uniforms.steps;
|
||
let dt_init = total_path / f32(steps_max);
|
||
let dt_min = dt_init * 0.25;
|
||
let dt_max = dt_init * 4.0;
|
||
let tol = 1e-3;
|
||
let r_plus = 0.5 + sqrt(max(0.25 - (uniforms.spin * 0.5) * (uniforms.spin * 0.5), 0.0));
|
||
|
||
var pos = rot_x(uniforms.eye.xyz, -uniforms.disk_tilt);
|
||
var d = normalize(rot_x(dir, -uniforms.disk_tilt));
|
||
var dt = dt_init;
|
||
var prev = pos;
|
||
var budget = steps_max;
|
||
|
||
var accum_color = vec3<f32>(0.0);
|
||
var accum_alpha = 0.0;
|
||
|
||
loop {
|
||
if (budget == 0u) { break; }
|
||
|
||
let step = rk45_step(pos, d, dt);
|
||
let err = step.err;
|
||
|
||
if (err > tol * 10.0 && dt > dt_min) {
|
||
// Reject: shrink dt, retry (does not consume budget).
|
||
// The `dt > dt_min` guard makes dt_min a forced-accept floor: once
|
||
// dt is already at its minimum, accept the step regardless of error
|
||
// rather than spinning forever on `continue`. This prevents a GPU
|
||
// hang when a ray hits a region whose error is intrinsically above
|
||
// tolerance even at the smallest step (extreme spin, near-horizon).
|
||
dt = dt_min;
|
||
continue;
|
||
}
|
||
// Accept: consume one budget unit, refine dt.
|
||
budget = budget - 1u;
|
||
if (err > tol * 10.0) {
|
||
// Forced accept at dt_min (err still high): don't grow dt back up.
|
||
} else {
|
||
dt = clamp(dt * pow(tol / max(err, 1e-12), 0.2), dt_min, dt_max);
|
||
}
|
||
|
||
let new_pos = step.pos;
|
||
let new_dir = step.dir;
|
||
|
||
let r = length(new_pos);
|
||
if (r < r_plus) {
|
||
break;
|
||
}
|
||
if (r > escape_r) {
|
||
let world_dir = normalize(rot_x(new_dir, uniforms.disk_tilt));
|
||
var bg = vec3<f32>(0.0);
|
||
bg += star_color(world_dir, uniforms.star_intensity);
|
||
if (uniforms.skybox_intensity > 0.0) {
|
||
bg += skybox_color(world_dir) * uniforms.skybox_intensity;
|
||
}
|
||
accum_color += (1.0 - accum_alpha) * bg;
|
||
accum_alpha = 1.0;
|
||
break;
|
||
}
|
||
|
||
// --- volumetric disk ---
|
||
if (uniforms.disk_quality == 0u) {
|
||
// Off tier: zero-thickness single midplane sample, fixed alpha.
|
||
if (disk_hit(prev, new_pos)) {
|
||
let ty = prev.y / (prev.y - new_pos.y);
|
||
let hit = mix(prev, new_pos, vec3<f32>(ty));
|
||
let s = disk_color_flat(hit, new_dir);
|
||
accum_color += (1.0 - accum_alpha) * s.color * s.density;
|
||
accum_alpha += (1.0 - accum_alpha) * s.density;
|
||
if (accum_alpha > 0.99) { break; }
|
||
}
|
||
} else {
|
||
// Volumetric tier.
|
||
// (A) In-slab per-step sampling: if this step ends inside the
|
||
// thickness slab, accumulate emission × arc length. Reuses the
|
||
// RK45 adaptive step — dense where light bends, sparse where straight.
|
||
let slab_r = r_of(new_pos);
|
||
if (abs(new_pos.y) < uniforms.disk_half_thickness
|
||
&& slab_r >= uniforms.disk_inner
|
||
&& slab_r <= uniforms.disk_outer) {
|
||
let s = disk_color_volumetric(new_pos, new_dir);
|
||
let step_len = length(new_pos - prev);
|
||
accum_color += (1.0 - accum_alpha) * s.color * s.density * step_len;
|
||
accum_alpha += (1.0 - accum_alpha) * s.density * step_len;
|
||
}
|
||
// (B) Midplane edge-capture: if a step straddles y=0, add one
|
||
// precise at-plane sample weighted by the slab depth along the ray.
|
||
if (disk_hit(prev, new_pos)) {
|
||
let ty = prev.y / (prev.y - new_pos.y);
|
||
let hit = mix(prev, new_pos, vec3<f32>(ty));
|
||
let s = disk_color_volumetric(hit, new_dir);
|
||
let thickness_proj = uniforms.disk_half_thickness / max(abs(new_dir.y), 1e-3);
|
||
accum_color += (1.0 - accum_alpha) * s.color * s.density * thickness_proj;
|
||
accum_alpha += (1.0 - accum_alpha) * s.density * thickness_proj;
|
||
}
|
||
if (accum_alpha > 0.99) { break; }
|
||
}
|
||
|
||
let ph = planet_hit(prev, new_pos, new_dir);
|
||
if (ph.w > 0.0) {
|
||
accum_color += (1.0 - accum_alpha) * ph.xyz * ph.w;
|
||
accum_alpha += (1.0 - accum_alpha) * ph.w;
|
||
if (accum_alpha > 0.99) { break; }
|
||
}
|
||
|
||
if (uniforms.grid_enabled != 0u) {
|
||
let g = grid_hit(prev, new_pos);
|
||
if (g.x + g.y + g.z > 0.0) {
|
||
accum_color += g;
|
||
}
|
||
}
|
||
|
||
prev = new_pos;
|
||
pos = new_pos;
|
||
d = new_dir;
|
||
}
|
||
|
||
return vec4<f32>(accum_color, 1.0);
|
||
}
|