Fake IBL

src/shader.wgsl

@@ -116,6 +116,45 @@ fn BRDF(
   return (Fr + Fd) * NoL;
 }
 
+fn sample_ibl_fake(
+  n_color: vec3<f32>,
+  s_color: vec3<f32>,
+  gradient: f32,
+  coords: vec3<f32>,
+) -> vec3<f32> {
+  let blend = coords.y / gradient + 0.5;
+  return mix(s_color, n_color, clamp(blend, 0.0, 1.0));
+}
+
+fn F_Schlick_Roughness(cos_theta: f32, f0: vec3<f32>, roughness: f32) -> vec3<f32> {
+  return f0 + (max(vec3<f32>(1.0 - roughness), f0) - f0) * pow(clamp(1.0 - cos_theta, 0.0, 1.0), 5.0);
+}
+
+let N_COLOR = vec3<f32>(0.7, 0.0, 1.0);
+let S_COLOR = vec3<f32>(0.1, 0.1, 0.1);
+let IBL_G = 1.0;
+
+fn fake_ibl(
+  n: vec3<f32>,      // normalized surface normal
+  v: vec3<f32>,      // normalized view direction
+  albedo: vec3<f32>, // surface albedo
+  metallic: f32,     // surface metallic
+  roughness: f32,    // surface roughness
+) -> vec3<f32> {
+  // calculate reflectance at surface incidence
+  let f0 = mix(vec3<f32>(0.04), albedo, metallic);
+  let kS = F_Schlick_Roughness(max(dot(n, v), 0.0), f0, roughness);
+  let kD = 1.0 - kS;
+  let diffuse = sample_ibl_fake(N_COLOR, S_COLOR, IBL_G, n);
+
+  let R = normalize(reflect(-v, n));
+  let specular = sample_ibl_fake(N_COLOR, S_COLOR, IBL_G, R);
+
+  let received = kD * diffuse + kS * specular;
+
+  return received * albedo;
+}
+
 [[stage(vertex)]]
 fn vs_main(
   [[builtin(instance_index)]] mesh_idx: u32,
@@ -162,5 +201,8 @@ fn fs_main(
     lum = lum + (radiance * reflected);
   }
 
-  return vec4<f32>(lum, 1.0);
+  lum = lum + fake_ibl(normal, view, albedo, metallic, roughness);
+
+  let tone_mapped = lum / (lum + 1.0);
+  return vec4<f32>(tone_mapped, 1.0);
 }