Remove HeavisideStep() from G_MaskingSmithGGX()

ScriptableRenderPipeline/Core/ShaderLibrary/BSDF.hlsl

 }
 
 // Ref: Understanding the Masking-Shadowing Function in Microfacet-Based BRDFs, p. 19, 29.
-float G_MaskingSmithGGX(float NdotV, float VdotH, float roughness)
+float G_MaskingSmithGGX(float NdotV, float roughness)
 {
     // G1(V, H)    = HeavisideStep(VdotH) / (1 + Λ(V)).
     // Λ(V)        = -0.5 + 0.5 * sqrt(1 + 1 / a²).
+    // Assume that (VdotH > 0), e.i. (acos(LdotV) < Pi).
-    float hs = VdotH > 0.0 ? 1.0 : 0.0;
-    return hs / (0.5 + 0.5 * sqrt(1.0 + a2 * (1.0 / z2 - 1.0)));
+    return 1 / (0.5 + 0.5 * sqrt(1.0 + a2 * (1.0 / z2 - 1.0)));
-float D_GGX_Visible(float NdotH, float NdotV, float VdotH, float roughness)
+float D_GGX_Visible(float NdotH, float NdotV, float roughness)
-    // Note that we pass 1.0 instead of 'VdotH' since the multiplication will already clamp.
-    return D_GGX(NdotH, roughness) * G_MaskingSmithGGX(NdotV, 1.0, roughness) * VdotH / NdotV;
+    return D_GGX(NdotH, roughness) * G_MaskingSmithGGX(NdotV, roughness) * VdotH / NdotV;
 }
 
 // Ref: http://jcgt.org/published/0003/02/03/paper.pdf