xfy
8931904495
Add planets as ray-traced spheres inside the RK4 geodesic loop. A new planets.wgsl shader tests each integrator segment against a storage buffer of SphereData (center/radius/color/emissive) and composites hits front-to-back alongside the accretion disk. Lambert shading with a fixed light direction; emissive flag bypasses shading. - assets/shaders/planets.wgsl: segment-sphere intersection + shading - src/scene/: Planet component, upload_planets system, default planet - black_hole.wgsl: wire planet_hit into the compositing loop - geodesic_schwarzschild.wgsl: replace tuple return with Deriv struct
47 lines
1.8 KiB
WebGPU Shading Language
47 lines
1.8 KiB
WebGPU Shading Language
struct SphereData {
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center: vec4<f32>, // xyz = center, w = radius
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color: vec4<f32>, // xyz = color, w = emissive flag (u32 reinterpreted; we just check > 0.5)
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};
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@group(#{MATERIAL_BIND_GROUP}) @binding(3) var<storage, read> planets: array<SphereData>;
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// Test the segment prev->cur against all planets. Returns hit color & alpha,
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// or (0,0,0,0) if no hit. `dir` is the ray direction (for shading).
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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 = s.center.xyz;
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let radius = s.center.w;
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// Ray-sphere intersection for the segment.
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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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// Lambert shading from a fixed light direction.
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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; } // emissive
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nearest_col = col;
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found = true;
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}
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}
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if (found) {
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return vec4<f32>(nearest_col, 0.95);
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}
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return vec4<f32>(0.0, 0.0, 0.0, 0.0);
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}
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