HDRenderPipeline: Finish to fix issue with AO

Store inverse AO in the buffer to to waste a sampler in lightloop

Assets/ScriptableRenderPipeline/HDRenderPipeline/Editor/SceneSettingsManagementWindow.cs

                 CreateAsset<CommonSettings>("NewCommonSettings");
             }
 
-            if (GUILayout.Button("Create new HDRI Sky params"))
+            if (GUILayout.Button("Create new HDRI Sky Settings"))
-            if (GUILayout.Button("Create new Procedural Sky params"))
+            if (GUILayout.Button("Create new Procedural Sky Settings"))
-                CreateAsset<ProceduralSkySettings>("NewProceduralSkyParameters");
+                CreateAsset<ProceduralSkySettings>("NewProceduralSkySettings");
-            if (GUILayout.Button("Create new Ambient Occlusion params"))
+            if (GUILayout.Button("Create new Ambient Occlusion Settings"))
-                CreateAsset<ScreenSpaceAmbientOcclusionSettings>("NewAmbientOcclusionParameters");
+                CreateAsset<ScreenSpaceAmbientOcclusionSettings>("NewAmbientOcclusionSettings");
             }
 
             EditorGUILayout.Space();

Assets/ScriptableRenderPipeline/HDRenderPipeline/Lighting/AmbientOcclusion/AmbientOcclusion.cs

             if (settings.enable == false || isForward)
             {
                 var cmd2 = new CommandBuffer { name = "Setup neutral Ambient Occlusion (1x1)" };
-                cmd2.SetGlobalTexture("_AmbientOcclusionTexture", PostProcessing.RuntimeUtilities.whiteTexture);
+                cmd2.SetGlobalTexture("_AmbientOcclusionTexture", PostProcessing.RuntimeUtilities.blackTexture); // Neutral is black, see the comment in the shaders
                 renderContext.ExecuteCommandBuffer(cmd2);
                 cmd2.Dispose();
 

Assets/ScriptableRenderPipeline/HDRenderPipeline/Lighting/AmbientOcclusion/Resources/Composition.hlsl

     ao += GetPackedAO(p4) * w4;
     ao /= w0 + w1 + w2 + w3 + w4;
 
-    return half4(1 - ao, 0, 0, 0);
+    // Note: When we ImageLoad outside of texture size, the value returned by Load is 0.
+    // We use this property to have a neutral value for AO that doesn't consume a sampler and work also with compute shader (i.e use ImageLoad)
+    // We store inverse AO so neutral is black. So either we sample inside or outside the texture it return 0 in case of neutral
+    return half4(ao, 0, 0, 0); // <= we don't invert ao here but when we sample the texture for reasons explain above
 }
 
 #endif // UNITY_HDRENDERPIPELINE_AMBIENTOCCLUSION_COMPOSITION

Assets/ScriptableRenderPipeline/HDRenderPipeline/Lighting/AmbientOcclusion/Resources/Estimation.hlsl

         ao += a1 / a2;
     }
 
-    // TODO: Check with Keijiro but ao is inverted here...
-    //ao = 1.0 - ao;
-
     // Apply intensity normalization/amplifier/contrast.
     ao = pow(max(0, ao * _Radius * _Intensity / _SampleCount), kContrast);
 

Assets/ScriptableRenderPipeline/HDRenderPipeline/Lighting/TilePass/TilePass.hlsl

 // ----------------------------------------------------------------------------
 
 TEXTURE2D(_AmbientOcclusionTexture);
-
-// TODO: Create a variant for it
-#define APPLY_AMBIENT_OCCLUSION

Assets/ScriptableRenderPipeline/HDRenderPipeline/Lighting/TilePass/TilePassLoop.hlsl

-//-----------------------------------------------------------------------------
+//-----------------------------------------------------------------------------
 // LightLoop
 // ----------------------------------------------------------------------------
 
                 out float3 specularLighting)
 {
     LightLoopContext context;
-    context.ambientOcclusion = 1; // LOAD_TEXTURE2D(_AmbientOcclusionTexture, posInput.unPositionSS).x;
+    // Note: When we ImageLoad outside of texture size, the value returned by Load is 0 (Note: On Metal maybe it clamp to value of texture which is also fine)
+    // We use this property to have a neutral value for AO that doesn't consume a sampler and work also with compute shader (i.e use ImageLoad)
+    // We store inverse AO so neutral is black. So either we sample inside or outside the texture it return 0 in case of neutral
+    context.ambientOcclusion = 1.0 - LOAD_TEXTURE2D(_AmbientOcclusionTexture, posInput.unPositionSS).x;
     context.sampleShadow = 0;
     context.sampleReflection = 0;
     context.shadowContext = InitShadowContext();
                 out float3 diffuseLighting,
                 out float3 specularLighting)
 {
-    LightLoopContext context;
-    context.ambientOcclusion = 1; // LOAD_TEXTURE2D(_AmbientOcclusionTexture, posInput.unPositionSS).x;
+    LightLoopContext context;    
+    // Note: When we ImageLoad outside of texture size, the value returned by Load is 0 (Note: On Metal maybe it clamp to value of texture which is also fine)
+    // We use this property to have a neutral value for AO that doesn't consume a sampler and work also with compute shader (i.e use ImageLoad)
+    // We store inverse AO so neutral is black. So either we sample inside or outside the texture it return 0 in case of neutral
+    context.ambientOcclusion = 1.0 - LOAD_TEXTURE2D(_AmbientOcclusionTexture, posInput.unPositionSS).x;
     context.sampleShadow = 0;
     context.sampleReflection = 0;
     context.shadowContext = InitShadowContext();

Assets/ScriptableRenderPipeline/HDRenderPipeline/RenderPipelineResources/DefaultAmbientOcclusionSettings.asset

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+    m_Enable: 1
+    m_Intensity: 1
+    m_Radius: 0.2
+    m_SampleCount: 8
+    m_Downsampling: 1

Assets/ScriptableRenderPipeline/HDRenderPipeline/RenderPipelineResources/DefaultAmbientOcclusionSettings.asset.meta

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