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ScriptableRenderPipeline/Core/ShaderLibrary/BSDF.hlsl

     float lightScatter = F_Schlick(1.0, fd90, NdotL);
     float viewScatter  = F_Schlick(1.0, fd90, NdotV);
 
-    // Normalize the BRDF for polar viewing angles up to (Pi/4).
-    // Hopefully the compiler folds the constant together with (1/Pi).
+    // Normalize the BRDF for polar view angles of up to (Pi/4).
+    // We use the worst case of (roughness = albedo = 1), and, for each view angle,
+    // integrate (brdf * cos(theta_light)) over all light directions.
+    // The resulting value is for (theta_view = 0), which is actually a little bit larger
+    // than the value of the integral for (theta_view = Pi/4).
+    // Hopefully, the compiler folds the constant together with (1/Pi).
     return rcp(1.03571) * (lightScatter * viewScatter);
 }