HDRP: Lighting - Fix shader warning + Remove comment

com.unity.render-pipelines.core/CoreRP/ShaderLibrary/Sampling/Sampling.hlsl

 //-----------------------------------------------------------------------------
 // Sampling function
 // Reference : http://www.cs.virginia.edu/~jdl/bib/globillum/mis/shirley96.pdf + PBRT
-// Caution: Our light point backward (-Z), these sampling function follow this convention
 //-----------------------------------------------------------------------------
 
 // Performs uniform sampling of the unit disk.
 {
     // Random point at rectangle surface
     P = real3((u.x - 0.5) * width, (u.y - 0.5) * height, 0);
-    Ns = real3(0, 0, -1); // Light point backward (-Z)
+    Ns = real3(0, 0, -1); // Light down (-Z)
 
     // Transform to world space
     P = mul(real4(P, 1.0), localToWorld).xyz;
 {
     // Random point at disk surface
     P  = real3(radius * SampleDiskUniform(u.x, u.y), 0);
-    Ns = real3(0.0, 0.0, -1.0); // Light point backward (-Z)
+    Ns = real3(0.0, 0.0, -1.0); // Light down (-Z)
 
     // Transform to world space
     P = mul(real4(P, 1.0), localToWorld).xyz;

com.unity.render-pipelines.core/CoreRP/ShaderLibrary/Shadow/PCSS.hlsl

         //        Overfiltering will leak results from other shadow lights.
         //TODO: Investigate moving this to blocker search.
         if (U <= UMin || U >= UMax || V <= VMin || V >= VMax)
-            sum += SampleCompShadow_T2DA(shadowContext, texIdx, sampIdx, real3(coord.xy, coord.z), slice);
+            sum += SampleCompShadow_T2DA(shadowContext, texIdx, sampIdx, real3(coord.xy, coord.z), slice).r;
-            sum += SampleCompShadow_T2DA(shadowContext, texIdx, sampIdx, real3(U, V, coord.z + dot(sampleBias, offset)), slice);
+            sum += SampleCompShadow_T2DA(shadowContext, texIdx, sampIdx, real3(U, V, coord.z + dot(sampleBias, offset)), slice).r;
     }
 
     return sum / sampleCount;
         //        Overfiltering will leak results from other shadow lights.
         //TODO: Investigate moving this to blocker search.
         if (U <= UMin || U >= UMax || V <= VMin || V >= VMax)
-            sum += SAMPLE_TEXTURE2D_ARRAY_SHADOW(shadowMap, compSampler, real3(coord.xy, coord.z), slice);
+            sum += SAMPLE_TEXTURE2D_ARRAY_SHADOW(shadowMap, compSampler, real3(coord.xy, coord.z), slice).r;
-            sum += SAMPLE_TEXTURE2D_ARRAY_SHADOW(shadowMap, compSampler, real3(U, V, coord.z + dot(sampleBias, offset)), slice);
+            sum += SAMPLE_TEXTURE2D_ARRAY_SHADOW(shadowMap, compSampler, real3(U, V, coord.z + dot(sampleBias, offset)), slice).r;
     }
 
     return sum / sampleCount;

com.unity.render-pipelines.high-definition/HDRP/Lighting/LightLoop/LightLoop.cs

 
             lightData.color = GetLightColor(light);
 
-            lightData.forward = light.light.transform.forward; // Note: Light direction is oriented backward (-Z)
+            lightData.forward = light.light.transform.forward;
             lightData.up = light.light.transform.up;
             lightData.right = light.light.transform.right;
 

com.unity.render-pipelines.high-definition/HDRP/Material/Lit/Lit.hlsl

     ZERO_INITIALIZE(DirectLighting, lighting);
 
     float3 N     = bsdfData.normalWS;
-    float3 L     = -lightData.forward; // Lights point backward in Unity
+    float3 L     = -lightData.forward;
     float  NdotL = dot(N, L);
 
     float3 transmittance = float3(0.0, 0.0, 0.0);

com.unity.render-pipelines.high-definition/HDRP/Material/StackLit/StackLit.hlsl

     float3 N; float unclampedNdotV;
     EvaluateBSDF_GetNormalUnclampedNdotV(bsdfData, preLightData, V, N, unclampedNdotV);
 
-    float3 L     = -lightData.forward; // Lights point backward in Unity
+    float3 L     = -lightData.forward;
     float  NdotL = dot(N, L);
 
     // For shadow attenuation (ie receiver bias), always use the geometric normal