Clean and comment some code

Assets/ScriptableRenderPipeline/HDRenderPipeline/Debug/DebugViewTiles.shader

                         n += count;
                     }
                 }
-                if(n == 0) n = -1;
+                if (n == 0)
+                    n = -1;
 #else
                 n = input.variant;
 #endif

Assets/ScriptableRenderPipeline/HDRenderPipeline/Lighting/TilePass/builddispatchindirect.compute

 	uint tileY = (dispatchThreadId + 0.5f) / (float)g_NumTilesX;	// Integer division is extremely expensive, so we better avoid it
 	uint tileX = dispatchThreadId - tileY * g_NumTilesX;
 
-	uint variant = FeatureFlagsToTileVariant(featureFlags);
-	uint offset;
-	InterlockedAdd(g_DispatchIndirectBuffer[variant * 3 + 0], 1, offset);
-	g_TileList[variant * g_NumTiles + offset] = (tileY << 16) | tileX;
+    // Check if there is no light or no material (mean we are sky/background pixel) / Both test as we can enable/disable light/material classification
+    if ((featureFlags & LIGHT_FEATURE_MASK_FLAGS) != 0 && (featureFlags & MATERIAL_FEATURE_MASK_FLAGS) != 0)
+    {
+        uint variant = FeatureFlagsToTileVariant(featureFlags);
+        uint offset;
+        InterlockedAdd(g_DispatchIndirectBuffer[variant * 3 + 0], 1, offset);
+        g_TileList[variant * g_NumTiles + offset] = (tileY << 16) | tileX;
+    }
 }

Assets/ScriptableRenderPipeline/HDRenderPipeline/Lighting/TilePass/lightlistbuild.compute

 	if(t == 0)
 	{
 		uint featureFlags = ldsFeatureFlags | g_BaseFeatureFlags;
+        // In case of back
-			featureFlags &= ~(LIGHTFEATUREFLAGS_PUNCTUAL | LIGHTFEATUREFLAGS_AREA | LIGHTFEATUREFLAGS_DIRECTIONAL | LIGHTFEATUREFLAGS_ENV | 0xFFFFF);	// list of features that are not enabled on background
+            // There is no stencil usage with compute path, featureFlags set to 0 is use to have fast rejection of tile in this case. It will still execute but will do nothing
+			featureFlags = 0;
 		}
 
 		g_TileFeatureFlags[tileIDX.y * nrTilesX + tileIDX.x] = featureFlags;

Assets/ScriptableRenderPipeline/HDRenderPipeline/Lighting/TilePass/materialflags.compute

 	}
 	GroupMemoryBarrierWithGroupSync();
 
-	uint materialFeatureFlags = g_BaseFeatureFlags;
+	uint materialFeatureFlags = g_BaseFeatureFlags; // Contain all lightFeatures or 0 (depends if we enable light classification or not)
 	[unroll]
 	for(int i = 0; i < 4; i++)
 	{
-		if (FetchDepth(g_depth_tex, uCrd) < VIEWPORT_SCALE_Z)
+		if (FetchDepth(g_depth_tex, uCrd) < VIEWPORT_SCALE_Z) // This test is we are the sky/background or not
 		{
 			PositionInputs posInput = GetPositionInput(uCrd, invScreenSize);
 			FETCH_GBUFFER(gbuffer, _GBufferTexture, posInput.unPositionSS);
 	{
 #ifdef USE_OR
 		g_TileFeatureFlags[tileIDX.y * nrTilesX + tileIDX.x] |= ldsFeatureFlags;
-#else
+#else // Use in case we have disabled light classification
 		g_TileFeatureFlags[tileIDX.y * nrTilesX + tileIDX.x] = ldsFeatureFlags;
 #endif
 	}

Assets/ScriptableRenderPipeline/HDRenderPipeline/Lighting/TilePass/shadeopaque.compute

 
     float depth = LOAD_TEXTURE2D(_MainDepthTexture, posInput.unPositionSS).x;
 
-    // TODO: add an early-out using HiZ/HiS or our light tile data.
-    if (depth == 0) { return; }
+    // For indirect case: we can still overlap inside a tile with the sky/background, reject it
+    // Can't rely on stencil as we are in compute shader
+    // TODO : if we have depth bounds test we could remove such a test ?
+    if (depth == UNITY_RAW_FAR_CLIP_VALUE)
+    {
+        return;
+    }
 
     UpdatePositionInput(depth, _InvViewProjMatrix, _ViewProjMatrix, posInput);
     float3 V = GetWorldSpaceNormalizeViewDir(posInput.positionWS);

Assets/ScriptableRenderPipeline/HDRenderPipeline/Material/Lit/Lit.hlsl

     /*  13 */ LIGHTFEATUREFLAGS_SKY | LIGHTFEATUREFLAGS_DIRECTIONAL | LIGHTFEATUREFLAGS_AREA | MATERIALFEATUREFLAGS_LIT_UNUSED0,
     /*  14 */ LIGHTFEATUREFLAGS_SKY | LIGHTFEATUREFLAGS_DIRECTIONAL | LIGHTFEATUREFLAGS_ENV | MATERIALFEATUREFLAGS_LIT_UNUSED0,
     ///*  15 */ LIGHT_FEATURE_MASK_FLAGS | MATERIALFEATUREFLAGS_LIT_UNUSED0
-    /* 15 */ 0xFFFFFFFF // LIGHT_FEATURE_MASK_FLAGS | MATERIAL_FEATURE_MASK_FLAGS, // Catch all case, but should not be needed
+    /* 15 */ LIGHT_FEATURE_MASK_FLAGS | MATERIAL_FEATURE_MASK_FLAGS, // Catch all case with MATERIAL_FEATURE_MASK_FLAGS is needed in case we disable material classification
 };
 
 uint FeatureFlagsToTileVariant(uint featureFlags)