Tweak the SSS energy preservation fix

Assets/ScriptableRenderPipeline/HDRenderPipeline/Material/Lit/Resources/CombineSubsurfaceScattering.shader

                 // TODO: ask Morten if there is a better way to do this.
                 float3 totalWeight = sampleWeight;
 
-                uint i;  // Sample index
-
-                [unroll] // Gather samples from the center to the left (up).
-                for (i = 1; i <= N_SAMPLES / 2; i++)
+                [unroll]
+                for (int i = 1; i < N_SAMPLES; i++)
                 {
                     samplePosition = posInput.unPositionSS + rotatedDirection * _FilterKernels[profileID][i].a;
                     sampleWeight   = _FilterKernels[profileID][i].rgb;
 
-                    if (any(sampleIrradiance) == false)
-                    {
-                        // The irradiance is 0. There could be two reasons for this.
-                        // Most likely, the surface fragment does not have an SSS material.
-                        // Alternatively, the surface fragment could be completely shadowed.
-                        // Our blur is energy-preserving, so 'sampleWeight' should be 0.
-                        // We can save some bandwidth by terminating the loop early.
-                        break;
-                    }
-
                     // Apply bilateral weighting.
                     // Ref #1: Skin Rendering by Pseudo–Separable Cross Bilateral Filtering.
                     // Ref #2: Separable SSS, Supplementary Materials, Section E.
 
-                    totalIrradiance += sampleWeight * sampleIrradiance;
-                    totalWeight     += sampleWeight;
-                }
-
-                [unroll] // Gather samples from the center to the right (down).
-                for (; i < N_SAMPLES; i++)
-                {
-                    samplePosition = posInput.unPositionSS + rotatedDirection * _FilterKernels[profileID][i].a;
-                    sampleWeight   = _FilterKernels[profileID][i].rgb;
-
-                    rawDepth         = LOAD_TEXTURE2D(_MainDepthTexture, samplePosition).r;
-                    sampleIrradiance = LOAD_TEXTURE2D(_IrradianceSource, samplePosition).rgb;
-
-                        // The irradiance is 0. There could be two reasons for this.
+                        // The irradiance is 0. This could happen for 2 reasons.
-                        // Our blur is energy-preserving, so 'sampleWeight' should be 0.
-                        // We can save some bandwidth by terminating the loop early.
-                        break;
+                        // Our blur is energy-preserving, so 'sampleWeight' should be set to 0.
+                        // We do not terminate the loop since we want to gather the contribution
+                        // of the remaining samples (e.g. in case of hair covering skin).
+                        continue;
-
-                    // Apply bilateral weighting.
-                    // Ref #1: Skin Rendering by Pseudo–Separable Cross Bilateral Filtering.
-                    // Ref #2: Separable SSS, Supplementary Materials, Section E.
-                    float sampleDepth = LinearEyeDepth(rawDepth, _ZBufferParams);
-                    float zDistance   = invDistScale * sampleDepth - (invDistScale * centerPosVS.z);
-                    sampleWeight     *= exp(-zDistance * zDistance * halfRcpVariance);
 
                     totalIrradiance += sampleWeight * sampleIrradiance;
                     totalWeight     += sampleWeight;