Texture-weighted automatic exposure (#165)

* Exposure weighted by texture

* miss one in the renaming

* Doc update

* changelog

* doc update

* fix issue when disabling override

Author: FrancescoC-unity

com.unity.render-pipelines.high-definition/CHANGELOG.md

@@ -105,6 +105,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - Added Light decomposition lighting debugging modes and support in AOV
 - Added exposure compensation to Fixed exposure mode
 - Added support for rasterized area light shadows in StackLit
+- Added support for texture-weighted automatic exposure
 
 ### Fixed
 - Fix when rescale probe all direction below zero (1219246)

com.unity.render-pipelines.high-definition/Documentation~/Override-Exposure.md

@@ -65,6 +65,9 @@ To configure **Automatic Mode**, select the **Metering Mode**. This tells the Ca
 
 ![](Images/Override-Exposure3.png)
 
+- **Mask Weighted**: The Camera applies a weight to every pixel in the buffer then uses the weights to measure the exposure. To specify the weighting, this technique uses the Texture set in the **Weight Texture Mask** field. Note that, if you do not provide a Texture, this metering mode is equivalent to **Average**.
+  
+
 Next, set the **Limit Min** and **Limit Max** to define the minimum and maximum exposure values respectively. Move between light and dark areas of your Scene and alter each property until you find the perfect values for your Scene.
 
 

com.unity.render-pipelines.high-definition/Editor/PostProcessing/ExposureEditor.cs

@@ -20,6 +20,8 @@ sealed class ExposureEditor : VolumeComponentEditor
         SerializedDataParameter m_AdaptationSpeedDarkToLight;
         SerializedDataParameter m_AdaptationSpeedLightToDark;
 
+        SerializedDataParameter m_WeightTextureMask;
+
         public override void OnEnable()
         {
             var o = new PropertyFetcher<Exposure>(serializedObject);
@@ -37,6 +39,8 @@ public override void OnEnable()
             m_AdaptationMode = Unpack(o.Find(x => x.adaptationMode));
             m_AdaptationSpeedDarkToLight = Unpack(o.Find(x => x.adaptationSpeedDarkToLight));
             m_AdaptationSpeedLightToDark = Unpack(o.Find(x => x.adaptationSpeedLightToDark));
+
+            m_WeightTextureMask = Unpack(o.Find(x => x.weightTextureMask));
         }
 
         public override void OnInspectorGUI()
@@ -58,6 +62,9 @@ public override void OnInspectorGUI()
                 EditorGUILayout.Space();
 
                 PropertyField(m_MeteringMode);
+                if(m_MeteringMode.value.intValue == (int)MeteringMode.MaskWeighted)
+                    PropertyField(m_WeightTextureMask);
+
                 PropertyField(m_LuminanceSource);
 
                 if (m_LuminanceSource.value.intValue == (int)LuminanceSource.LightingBuffer)

com.unity.render-pipelines.high-definition/Runtime/PostProcessing/Components/Exposure.cs

@@ -85,6 +85,12 @@ public sealed class Exposure : VolumeComponent, IPostProcessComponent
         [Tooltip("Sets the speed at which the exposure changes when the Camera moves from a bright area to a dark area.")]
         public MinFloatParameter adaptationSpeedLightToDark = new MinFloatParameter(1f, 0.001f);
 
+        /// <summary>
+        /// Sets the texture mask used to weight the pixels in the buffer when computing exposure. Used only with .
+        /// </summary>
+        [Tooltip("Sets the texture mask to be used to weight the pixels in the buffer for the sake of computing exposure..")]
+        public NoInterpTextureParameter weightTextureMask = new NoInterpTextureParameter(null);
+
         /// <summary>
         /// Tells if the effect needs to be rendered or not.
         /// </summary>
@@ -145,7 +151,16 @@ public enum MeteringMode
         /// have the minimum weight, and pixels in between have a progressively lower weight the
         /// closer they are to the screen borders.
         /// </summary>
-        CenterWeighted
+        CenterWeighted,
+
+
+        /// <summary>
+        /// The Camera applies a weight to every pixel in the buffer and then uses them to measure
+        /// the exposure. The weighting is specified by the texture provided by the user. Note that if
+        /// no texture is provided, then this metering mode is equivalent to Average.
+        /// </summary>
+        MaskWeighted
+
     }
 
     /// <summary>

com.unity.render-pipelines.high-definition/Runtime/PostProcessing/PostProcessSystem.cs

@@ -873,6 +873,14 @@ void DoDynamicExposure(CommandBuffer cmd, HDCamera camera, RTHandle colorBuffer)
             cmd.SetComputeIntParams(cs, HDShaderIDs._Variants, m_ExposureVariants);
             cmd.SetComputeTextureParam(cs, kernel, HDShaderIDs._PreviousExposureTexture, prevExposure);
             cmd.SetComputeTextureParam(cs, kernel, HDShaderIDs._SourceTexture, sourceTex);
+            if (m_Exposure.meteringMode == MeteringMode.MaskWeighted && m_Exposure.weightTextureMask.value != null)
+            {
+                cmd.SetComputeTextureParam(cs, kernel, HDShaderIDs._ExposureWeightMask, m_Exposure.weightTextureMask.value);
+            }
+            else
+            {
+                cmd.SetComputeTextureParam(cs, kernel, HDShaderIDs._ExposureWeightMask, Texture2D.whiteTexture);
+            }
             cmd.SetComputeTextureParam(cs, kernel, HDShaderIDs._OutputTexture, m_TempTexture1024);
             cmd.DispatchCompute(cs, kernel, 1024 / 8, 1024 / 8, 1);
 

com.unity.render-pipelines.high-definition/Runtime/PostProcessing/Shaders/Exposure.compute

@@ -14,6 +14,9 @@
 TEXTURE2D(_ExposureCurveTexture);
 TEXTURE2D(_PreviousExposureTexture);
 TEXTURE2D(_InputTexture);
+
+TEXTURE2D(_ExposureWeightMask);
+
 TEXTURE2D_X(_SourceTexture);
 
 RW_TEXTURE2D(float2, _OutputTexture);
@@ -42,6 +45,9 @@ CBUFFER_END
 #define ParamAdaptationMode         _Variants.z
 #define ParamEvaluateMode           _Variants.w
 
+#define PREPASS_TEX_SIZE 1024.0
+#define PREPASS_TEX_HALF_SIZE 512.0
+
 float WeightSample(uint2 pixel)
 {
     UNITY_BRANCH
@@ -50,17 +56,23 @@ float WeightSample(uint2 pixel)
         case 1u:
         {
             // Spot metering
-            const float kRadius = 0.075 * 1024.0;
-            const float2 kCenter = (512.0).xx;
+            const float kRadius = 0.075 * PREPASS_TEX_SIZE;
+            const float2 kCenter = (PREPASS_TEX_HALF_SIZE).xx;
             float d = length(kCenter - pixel) - kRadius;
             return 1.0 - saturate(d);
         }
         case 2u:
         {
             // Center-weighted
-            const float2 kCenter = (512.0).xx;
-            return 1.0 - saturate(pow(length(kCenter - pixel) / 512.0, 1.0));
+            const float2 kCenter = (PREPASS_TEX_HALF_SIZE).xx;
+            return 1.0 - saturate(pow(length(kCenter - pixel) / PREPASS_TEX_HALF_SIZE, 1.0));
         }
+        case 3u:
+        {
+            // Mask weigthing
+            return SAMPLE_TEXTURE2D_LOD(_ExposureWeightMask, sampler_LinearClamp, pixel * rcp(PREPASS_TEX_SIZE), 0.0).x;
+        }
+
         default:
         {
             // Global average
@@ -126,7 +138,7 @@ void KPrePass(uint2 dispatchThreadId : SV_DispatchThreadID)
     // For XR, interleave single-pass views in a checkerboard pattern
     UNITY_XR_ASSIGN_VIEW_INDEX((dispatchThreadId.x + dispatchThreadId.y) % _XRViewCount)
 
-    PositionInputs posInputs = GetPositionInput(float2(dispatchThreadId), 1.0 / 1024.0, uint2(8u, 8u));
+    PositionInputs posInputs = GetPositionInput(float2(dispatchThreadId), rcp(PREPASS_TEX_SIZE), uint2(8u, 8u));
     float2 uv = ClampAndScaleUVForBilinear(posInputs.positionNDC);
     float luma;
 

com.unity.render-pipelines.high-definition/Runtime/RenderPipeline/HDStringConstants.cs

@@ -596,6 +596,7 @@ static class HDShaderIDs
         public static readonly int _ExposureParams                 = Shader.PropertyToID("_ExposureParams");
         public static readonly int _AdaptationParams               = Shader.PropertyToID("_AdaptationParams");
         public static readonly int _ExposureCurveTexture           = Shader.PropertyToID("_ExposureCurveTexture");
+        public static readonly int _ExposureWeightMask             = Shader.PropertyToID("_ExposureWeightMask");
         public static readonly int _Variants                       = Shader.PropertyToID("_Variants");
         public static readonly int _InputTexture                   = Shader.PropertyToID("_InputTexture");
         public static readonly int _OutputTexture                  = Shader.PropertyToID("_OutputTexture");