68 lines
1.7 KiB
WebGPU Shading Language
68 lines
1.7 KiB
WebGPU Shading Language
let PI: f32 = 3.141592;
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fn D_GGX(NoH: f32, roughness: f32) -> f32 {
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let a = roughness * roughness;
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let a2 = a * a;
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let NoH2 = NoH * NoH;
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let f = NoH * (a2 - 1.0) + 1.0;
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return a2 / (PI * f * f);
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}
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fn g1(NoV: f32, roughness: f32, k: f32) -> f32 {
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let denom = NoV * (1.0 - k) + k;
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return NoV / denom;
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}
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fn G_SmithGGXCorrelated(NoV: f32, NoL: f32, roughness: f32) -> f32 {
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let r = roughness + 1.0;
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let k = (r * r) / 8.0;
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let g1l = g1(NoV, roughness, k);
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let g1v = g1(NoL, roughness, k);
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return g1l * g1v;
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}
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fn F_Schlick(u: f32, f0: vec3<f32>) -> vec3<f32> {
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let f = pow(1.0 - u, 5.0);
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return f + f0 * (1.0 - f);
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}
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fn BRDF(
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l: vec3<f32>, // normalized light direction
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n: vec3<f32>, // normalized surface normal
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v: vec3<f32>, // normalized view direction
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albedo: vec3<f32>, // surface albedo
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metallic: f32, // surface metallic
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roughness: f32, // surface roughness
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) -> vec3<f32> {
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let h = normalize(v + l);
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let NoL = max(dot(n, l), 0.0);
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let NoV = max(dot(n, v), 0.0);
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let NoH = max(dot(n, h), 0.0);
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let LoH = max(dot(l, h), 0.0);
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// calculate reflectance at surface incidence
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let f0 = mix(vec3<f32>(0.04), albedo, metallic);
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// specular BRDF
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let D = D_GGX(NoH, roughness);
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let G = G_SmithGGXCorrelated(NoV, NoL, roughness);
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let F = F_Schlick(LoH, f0);
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let numerator = (D * G) * F;
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let denominator = 4.0 * NoV * NoL;
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let Fr = numerator / max(denominator, 0.01);
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// diffuse BRDF
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let diffuse_fresnel =
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(vec3<f32>(1.0) - F_Schlick(NoL, f0)) *
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(vec3<f32>(1.0) - F_Schlick(NoV, f0));
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let lambertian = albedo / PI;
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let Fd = diffuse_fresnel * lambertian;
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// TODO multiple scattering
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return (Fr + Fd) * NoL;
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} |