Exposure curve remapping can specify curves for min/max limits

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

@@ -152,6 +152,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - Added compute shader stripping.
 - Added Cull Mode option for opaque materials and ShaderGraphs. 
 - Added scene view exposure override.
+- Added support for exposure curve remapping for min/max limits.
 
 ### Fixed
 - Fix when rescale probe all direction below zero (1219246)

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

@@ -16,7 +16,9 @@ sealed class ExposureEditor : VolumeComponentEditor
         SerializedDataParameter m_LimitMin;
         SerializedDataParameter m_LimitMax;
         SerializedDataParameter m_CurveMap;
-
+        SerializedDataParameter m_CurveMin;
+        SerializedDataParameter m_CurveMax;
+
         SerializedDataParameter m_AdaptationMode;
         SerializedDataParameter m_AdaptationSpeedDarkToLight;
         SerializedDataParameter m_AdaptationSpeedLightToDark;
@@ -52,7 +54,9 @@ public override void OnEnable()
             m_LimitMin = Unpack(o.Find(x => x.limitMin));
             m_LimitMax = Unpack(o.Find(x => x.limitMax));
             m_CurveMap = Unpack(o.Find(x => x.curveMap));
-
+            m_CurveMin = Unpack(o.Find(x => x.limitMinCurveMap));
+            m_CurveMax = Unpack(o.Find(x => x.limitMaxCurveMap));
+
             m_AdaptationMode = Unpack(o.Find(x => x.adaptationMode));
             m_AdaptationSpeedDarkToLight = Unpack(o.Find(x => x.adaptationSpeedDarkToLight));
             m_AdaptationSpeedLightToDark = Unpack(o.Find(x => x.adaptationSpeedLightToDark));
@@ -137,11 +141,18 @@ public override void OnInspectorGUI()
                 //    EditorGUILayout.HelpBox("Luminance source buffer isn't supported yet.", MessageType.Warning);
 
                 if (mode == (int)ExposureMode.CurveMapping)
+                {
                     PropertyField(m_CurveMap);
-
+                    PropertyField(m_CurveMin, EditorGUIUtility.TrTextContent("Limit Min"));
+                    PropertyField(m_CurveMax, EditorGUIUtility.TrTextContent("Limit Max"));
+                }
+                else if (!(mode == (int)ExposureMode.AutomaticHistogram && m_HistogramCurveRemapping.value.boolValue))
+                {
+                    PropertyField(m_LimitMin);
+                    PropertyField(m_LimitMax);
+                }
+
                 PropertyField(m_Compensation);
-                PropertyField(m_LimitMin);
-                PropertyField(m_LimitMax);
 
                 if(mode == (int)ExposureMode.AutomaticHistogram)
                 {
@@ -152,6 +163,8 @@ public override void OnInspectorGUI()
                     if (m_HistogramCurveRemapping.value.boolValue)
                     {
                         PropertyField(m_CurveMap);
+                        PropertyField(m_CurveMin, EditorGUIUtility.TrTextContent("Limit Min"));
+                        PropertyField(m_CurveMax, EditorGUIUtility.TrTextContent("Limit Max"));
                     }
                 }
 

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

@@ -64,6 +64,20 @@ public sealed class Exposure : VolumeComponent, IPostProcessComponent
         [Tooltip("Specifies a curve that remaps the Scene exposure on the x-axis to the exposure you want on the y-axis.")]
         public AnimationCurveParameter curveMap = new AnimationCurveParameter(AnimationCurve.Linear(-10f, -10f, 20f, 20f)); // TODO: Use TextureCurve instead?
 
+        /// <summary>
+        /// Specifies a curve that determines for each current exposure value (x-value) what minimum value is allowed to auto-adaptation (y-axis).
+        /// This parameter is only used when <see cref="ExposureMode.CurveMapping"/> is set.
+        /// </summary>
+        [Tooltip("Specifies a curve that determines for each current exposure value (x-value) what minimum value is allowed to auto-adaptation (y-axis).")]
+        public AnimationCurveParameter limitMinCurveMap = new AnimationCurveParameter(AnimationCurve.Linear(-10f, -12f, 20f, 18f));
+
+        /// <summary>
+        /// Specifies a curve that determines for each current exposure value (x-value) what maximum value is allowed to auto-adaptation (y-axis).
+        /// This parameter is only used when <see cref="ExposureMode.CurveMapping"/> is set.
+        /// </summary>
+        [Tooltip("Specifies a curve that determines for each current exposure value (x-value) what maximum value is allowed to auto-adaptation (y-axis).")]
+        public AnimationCurveParameter limitMaxCurveMap = new AnimationCurveParameter(AnimationCurve.Linear(-10f, -8f, 20f, 22f));
+
         /// <summary>
         /// Specifies the method that HDRP uses to change the exposure when the Camera moves from dark to light and vice versa.
         /// This parameter is only used when <see cref="ExposureMode.Automatic"/> or <see cref="ExposureMode.CurveMapping"/> is set.

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

@@ -1017,18 +1017,27 @@ RTHandle Allocator(string id, int frameIndex, RTHandleSystem rtHandleSystem)
             previous = camera.GetPreviousFrameRT((int)HDCameraFrameHistoryType.Exposure);
         }
 
-        void PrepareExposureCurveData(AnimationCurve curve, out float min, out float max)
+        void PrepareExposureCurveData(out float min, out float max)
         {
+            var curve = m_Exposure.curveMap.value;
+            var minCurve = m_Exposure.limitMinCurveMap.value;
+            var maxCurve = m_Exposure.limitMaxCurveMap.value;
+
             if (m_ExposureCurveTexture == null)
             {
-                m_ExposureCurveTexture = new Texture2D(k_ExposureCurvePrecision, 1, TextureFormat.RHalf, false, true)
+                m_ExposureCurveTexture = new Texture2D(k_ExposureCurvePrecision, 1, TextureFormat.RGBAHalf, false, true)
                 {
                     name = "Exposure Curve",
                     filterMode = FilterMode.Bilinear,
                     wrapMode = TextureWrapMode.Clamp
                 };
             }
 
+            bool minCurveHasPoints = minCurve.length > 0;
+            bool maxCurveHasPoints = maxCurve.length > 0;
+            float defaultMin = -100.0f;
+            float defaultMax = 100.0f;
+
             var pixels = m_ExposureCurveColorArray;
 
             // Fail safe in case the curve is deleted / has 0 point
@@ -1047,7 +1056,13 @@ void PrepareExposureCurveData(AnimationCurve curve, out float min, out float max
                 float step = (max - min) / (k_ExposureCurvePrecision - 1f);
 
                 for (int i = 0; i < k_ExposureCurvePrecision; i++)
-                    pixels[i] = new Color(curve.Evaluate(min + step * i), 0f, 0f, 0f);
+                {
+                    float currTime = min + step * i;
+                    pixels[i] = new Color(curve.Evaluate(currTime),
+                                          minCurveHasPoints ? minCurve.Evaluate(currTime) : defaultMin,
+                                          maxCurveHasPoints ? maxCurve.Evaluate(currTime) : defaultMax,
+                                          0f);
+                }
             }
 
             m_ExposureCurveTexture.SetPixels(pixels);
@@ -1124,7 +1139,7 @@ void DoDynamicExposure(CommandBuffer cmd, HDCamera camera, RTHandle colorBuffer)
             }
             else if (m_Exposure.mode.value == ExposureMode.CurveMapping)
             {
-                PrepareExposureCurveData(m_Exposure.curveMap.value, out float min, out float max);
+                PrepareExposureCurveData(out float min, out float max);
                 cmd.SetComputeTextureParam(cs, kernel, HDShaderIDs._ExposureCurveTexture, m_ExposureCurveTexture);
                 cmd.SetComputeVectorParam(cs, HDShaderIDs._ExposureParams, new Vector4(m_Exposure.compensation.value + m_DebugExposureCompensation, min, max, 0f));
                 cmd.SetComputeVectorParam(cs, HDShaderIDs._ExposureParams2, new Vector4(min, max, ColorUtils.lensImperfectionExposureScale, ColorUtils.s_LightMeterCalibrationConstant));
@@ -1199,7 +1214,7 @@ void DoHistogramBasedExposure(CommandBuffer cmd, HDCamera camera, RTHandle sourc
             m_ExposureVariants[3] = 0;
             if (m_Exposure.histogramUseCurveRemapping.value)
             {
-                PrepareExposureCurveData(m_Exposure.curveMap.value, out float min, out float max);
+                PrepareExposureCurveData(out float min, out float max);
                 cmd.SetComputeVectorParam(cs, HDShaderIDs._ExposureParams2, new Vector4(min, max, ColorUtils.lensImperfectionExposureScale, ColorUtils.s_LightMeterCalibrationConstant));
                 m_ExposureVariants[3] = 2;
             }

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

@@ -127,8 +127,11 @@ void KReduction(uint2 groupId : SV_GroupID, uint2 groupThreadId : SV_GroupThread
             case 2u:
             {
                 // Curve remapping
-                float exposure = CurveRemap(avgLuminance);
+                float minExposure = ParamExposureLimitMin;
+                float maxExposure = ParamExposureLimitMax;
+                float exposure = CurveRemap(avgLuminance, minExposure, maxExposure);
                 exposure = AdaptExposure(exposure - ParamExposureCompensation);
+                exposure = clamp(exposure, minExposure, maxExposure);
                 _OutputTexture[groupId.xy] = float2(ConvertEV100ToExposure(exposure, LensImperfectionExposureScale), exposure);
                 break;
             }

com.unity.render-pipelines.high-definition/Runtime/PostProcessing/Shaders/ExposureCommon.hlsl

@@ -122,10 +122,13 @@ float AdaptExposure(float exposure)
     }
 }
 
-float CurveRemap(float inEV)
+float CurveRemap(float inEV, out float limitMin, out float limitMax)
 {
     float remap = saturate((inEV - ParamCurveMin) / (ParamCurveMax - ParamCurveMin));
-    return SAMPLE_TEXTURE2D_LOD(_ExposureCurveTexture, s_linear_clamp_sampler, float2(remap, 0.0), 0.0).x;
+    float3 curveSample = SAMPLE_TEXTURE2D_LOD(_ExposureCurveTexture, s_linear_clamp_sampler, float2(remap, 0.0), 0.0).xyz;
+    limitMin = curveSample.y;
+    limitMax = curveSample.z;
+    return curveSample.x;
 }
 
 #endif

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

@@ -165,13 +165,15 @@ void KHistogramReduce(uint3 dispatchThreadId : SV_DispatchThreadID)
         w = max(w, 1e-4f);
         float avgEV = evProcessedSum * rcp(w);
 
+        float minExposure = ParamExposureLimitMin;
+        float maxExposure = ParamExposureLimitMax;
         if (ParamEvaluateMode == 2)
         {
-            avgEV = CurveRemap(avgEV);
+            avgEV = CurveRemap(avgEV, minExposure, maxExposure);
         }
 
         float exposure = AdaptExposure(avgEV - ParamExposureCompensation);
-        exposure = clamp(exposure, ParamExposureLimitMin, ParamExposureLimitMax);
+        exposure = clamp(exposure, minExposure, maxExposure);
         _OutputTexture[uint2(0, 0)] = float2(ConvertEV100ToExposure(exposure, LensImperfectionExposureScale), exposure);
 #ifdef OUTPUT_DEBUG_DATA
         _ExposureDebugTexture[uint2(0, 0)] = float2(avgEV - ParamExposureCompensation, 0.0f);