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refactor(shader): extract disk helpers, add DiskSample + flat fallback

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Splits disk_color into shared helpers (temperature_color, radial_falloff,
apply_doppler, r_of) reused by both the flat and volumetric paths.
disk_color_flat returns a DiskSample with the old fixed 0.85 alpha,
preserving the exact pre-volumetric appearance behind the Off tier. A
temporary disk_color shim keeps the main-loop call site compiling until
Task 7 restructures it.
This commit is contained in:
xfy 2026-07-15 13:29:48 +08:00
parent c9cc2eec99
commit de4ceee8ff
1 changed files with 51 additions and 18 deletions
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69
assets/shaders/black_hole.wgsl
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@ -252,10 +252,49 @@ fn disk_noise(pos: vec3<f32>, t: f32) -> f32 {
return n;
}
fn disk_color(pos: vec3<f32>, dir: vec3<f32>) -> vec3<f32> {
let r = length(vec2<f32>(pos.x, pos.z));
let phi = atan2(pos.z, pos.x);
// Result of a disk color query: emitted radiance + opacity contribution.
// Both the volumetric and flat paths return this struct so the main loop
// can treat them uniformly.
struct DiskSample {
color: vec3<f32>,
density: f32,
}
// Radial temperature gradient: white-hot inner → deep-orange outer.
fn temperature_color(t: f32) -> vec3<f32> {
return mix(vec3<f32>(1.0, 0.95, 0.85), vec3<f32>(1.0, 0.45, 0.12), clamp(t, 0.0, 1.0));
}
// Radial brightness falloff (∝ 1/r² from the inner edge).
fn radial_falloff(r: f32, inner: f32) -> f32 {
return 1.0 / pow(r / inner, 2.0);
}
// Cylindrical radius in the disk plane.
fn r_of(pos: vec3<f32>) -> f32 {
return length(vec2<f32>(pos.x, pos.z));
}
// Relativistic Doppler beaming. `dir` is the ray direction (disk-local).
fn apply_doppler(col: vec3<f32>, pos: vec3<f32>, dir: vec3<f32>) -> vec3<f32> {
let phi = atan2(pos.z, pos.x);
let v_orbital = sqrt(uniforms.rs / (2.0 * r_of(pos)));
let tangent = normalize(vec3<f32>(-sin(phi), 0.0, cos(phi)));
let vdotn = dot(tangent * v_orbital, -dir);
let gamma = 1.0 / sqrt(max(1.0 - v_orbital * v_orbital, 1e-4));
if (uniforms.doppler_enabled == 0u) {
return col;
}
let delta = 1.0 / (gamma * (1.0 - vdotn));
let doppler = pow(delta, 3.0) * uniforms.doppler_strength;
return col * doppler;
}
// Off-tier fallback: zero-thickness disk, single sample, fixed alpha.
// Preserves the exact pre-volumetric appearance. Returns DiskSample so the
// main loop dispatches both paths uniformly.
fn disk_color_flat(pos: vec3<f32>, dir: vec3<f32>) -> DiskSample {
let r = r_of(pos);
let rot = uniforms.time * uniforms.disk_rotation_speed / pow(r, 1.5);
// Domain-warped FBM for feathered/smoky gas texture. The Keplerian shear
// (rot ∝ 1/r^1.5) is folded into the noise flow term so inner radii flow
@ -263,24 +302,18 @@ fn disk_color(pos: vec3<f32>, dir: vec3<f32>) -> vec3<f32> {
let noise = disk_noise(vec3<f32>(pos.x * 0.3, pos.z * 0.3, rot), uniforms.time);
let t = (r - uniforms.disk_inner) / (uniforms.disk_outer - uniforms.disk_inner);
let tcol = mix(vec3<f32>(1.0, 0.95, 0.85), vec3<f32>(1.0, 0.45, 0.12), clamp(t, 0.0, 1.0));
let tcol = temperature_color(t);
let falloff = radial_falloff(r, uniforms.disk_inner);
let falloff = 1.0 / pow(r / uniforms.disk_inner, 2.0);
var col = tcol * (0.6 + 0.4 * noise) * falloff * uniforms.disk_brightness;
col = apply_doppler(col, pos, dir);
var col = tcol * (0.6 + 0.4 * noise) * falloff;
return DiskSample(vec3<f32>(col), 0.85);
}
let v_orbital = sqrt(uniforms.rs / (2.0 * r));
let tangent = normalize(vec3<f32>(-sin(phi), 0.0, cos(phi)));
let vdotn = dot(tangent * v_orbital, -dir);
let gamma = 1.0 / sqrt(max(1.0 - v_orbital * v_orbital, 1e-4));
var doppler = 1.0;
if (uniforms.doppler_enabled != 0u) {
let delta = 1.0 / (gamma * (1.0 - vdotn));
doppler = pow(delta, 3.0) * uniforms.doppler_strength;
}
col *= doppler;
return col * uniforms.disk_brightness;
// TEMPORARY shim — removed in Task 7 when the main loop is restructured.
fn disk_color(pos: vec3<f32>, dir: vec3<f32>) -> vec3<f32> {
return disk_color_flat(pos, dir).color;
}
// --- planets ---