Fix emissive color when switching from ldr to HDR

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

@@ -18,6 +18,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - Fixed missing DisallowMultipleComponent annotations in HDAdditionalReflectionData and HDAdditionalLightData (case 1365879).
 - Fixed support for light/shadow dimmers (volumetric or not) in path tracing.
 - Fixed ambient occlusion strenght incorrectly using GTAOMultiBounce
+- Fixed emissive value when switching between HDR and LDR mode.
 
 ## [12.0.0] - 2021-01-11
 

com.unity.render-pipelines.high-definition/Editor/Material/UIBlocks/DecalSurfaceInputsUIBlock.cs

@@ -281,18 +281,24 @@ protected override void OnGUIOpen()
 
                 if (useEmissiveIntensity.floatValue == 0.0f)
                 {
+                    if (updateEmissiveColor)
+                        emissiveColorHDR.colorValue = emissiveColor.colorValue;
+
                     EditorGUI.BeginChangeCheck();
                     EmissionUIBlock.DoEmissiveTextureProperty(materialEditor, emissiveColorMap, emissiveColorHDR);
-                    if (EditorGUI.EndChangeCheck() || updateEmissiveColor)
+                    if (EditorGUI.EndChangeCheck())
                         emissiveColor.colorValue = emissiveColorHDR.colorValue;
                 }
                 else
                 {
+                    if (updateEmissiveColor)
+                        EmissionUIBlock.UpdateEmissiveColorLDRAndIntensityFromEmissiveColor(emissiveColorLDR, emissiveIntensity, emissiveColor);
+
                     EditorGUI.BeginChangeCheck();
                     EmissionUIBlock.DoEmissiveTextureProperty(materialEditor, emissiveColorMap, emissiveColorLDR);
                     EmissionUIBlock.DoEmissiveIntensityGUI(materialEditor, emissiveIntensity, emissiveIntensityUnit);
                     if (EditorGUI.EndChangeCheck() || updateEmissiveColor)
-                        EmissionUIBlock.UpdateEmissiveColorFromIntensityAndEmissiveColorLDR(materialEditor, materials);
+                        EmissionUIBlock.UpdateEmissiveColorFromIntensityAndEmissiveColorLDR(emissiveColorLDR, emissiveIntensity, emissiveColor);
                 }
 
                 materialEditor.ShaderProperty(emissiveExposureWeight, Styles.emissiveExposureWeightText);

com.unity.render-pipelines.high-definition/Editor/Material/UIBlocks/EmissionUIBlock.cs

@@ -108,33 +108,40 @@ public override void LoadMaterialProperties()
             UVMappingMaskEmissive = FindProperty(kUVMappingMaskEmissive);
         }
 
-        internal static void UpdateEmissiveColorFromIntensityAndEmissiveColorLDR(MaterialEditor materialEditor, Material[] materials)
-        {
-            materialEditor.serializedObject.ApplyModifiedProperties();
-            foreach (Material target in materials)
-            {
-                target.UpdateEmissiveColorFromIntensityAndEmissiveColorLDR();
-            }
-            materialEditor.serializedObject.Update();
-        }
-
         internal static void UpdateEmissiveColorFromIntensityAndEmissiveColorLDR(MaterialProperty emissiveColorLDR, MaterialProperty emissiveIntensity, MaterialProperty emissiveColor)
             => emissiveColor.colorValue = emissiveColorLDR.colorValue.linear * emissiveIntensity.floatValue;
 
-        internal static void UpdateEmissiveColorLDRFromIntensityAndEmissiveColor(MaterialEditor materialEditor, Material[] materials)
+        internal static void UpdateEmissiveColorLDRAndIntensityFromEmissiveColor(MaterialProperty emissiveColorLDR, MaterialProperty emissiveIntensity, MaterialProperty emissiveColor)
         {
-            materialEditor.serializedObject.ApplyModifiedProperties();
-            foreach (Material target in materials)
+            // specifies the max byte value to use when decomposing a float color into bytes with exposure
+            // this is the value used by Photoshop
+            const byte k_MaxByteForOverexposedColor = 191;
+
+            float intensity = 1f;
+            Color colorHDR = emissiveColor.colorValue;
+            Color colorLDR = colorHDR;
+
+            var maxColorComponent = emissiveColor.colorValue.maxColorComponent;
+            if (maxColorComponent != 0f)
             {
-                target.UpdateEmissiveColorLDRFromIntensityAndEmissiveColor();
+                int maxColorComponentIndex = 0;
+                if (colorLDR.r > colorLDR.g) maxColorComponentIndex = colorLDR.r > colorLDR.b ? 0 : 2;
+                if (colorLDR.g > colorLDR.r) maxColorComponentIndex = colorLDR.g > colorLDR.b ? 1 : 2;
+
+                // calibrate exposure to the max float color component
+                var scaleFactor = k_MaxByteForOverexposedColor / maxColorComponent;
+
+                // maintain maximal integrity of byte values to prevent off-by-one errors when scaling up a color one component at a time
+                colorLDR.r = Math.Min(k_MaxByteForOverexposedColor, (byte)Mathf.CeilToInt(scaleFactor * colorHDR.r)) / 255f;
+                colorLDR.g = Math.Min(k_MaxByteForOverexposedColor, (byte)Mathf.CeilToInt(scaleFactor * colorHDR.g)) / 255f;
+                colorLDR.b = Math.Min(k_MaxByteForOverexposedColor, (byte)Mathf.CeilToInt(scaleFactor * colorHDR.b)) / 255f;
+
+                intensity = colorHDR[maxColorComponentIndex] / colorLDR[maxColorComponentIndex];
             }
-            materialEditor.serializedObject.Update();
-        }
 
-        internal static void UpdateEmissiveColorLDRFromIntensityAndEmissiveColor(MaterialProperty emissiveColorLDR, MaterialProperty emissiveIntensity, MaterialProperty emissiveColor)
-        {
-            Color emissiveColorLDRLinear = emissiveColor.colorValue / emissiveIntensity.floatValue;
-            emissiveColorLDR.colorValue = emissiveColorLDRLinear.gamma;
+            colorLDR.a = 1.0f;
+            emissiveIntensity.floatValue = intensity;
+            emissiveColorLDR.colorValue = colorLDR.gamma;
         }
 
         internal static void DoEmissiveIntensityGUI(MaterialEditor materialEditor, MaterialProperty emissiveIntensity, MaterialProperty emissiveIntensityUnit)
@@ -205,7 +212,7 @@ protected override void OnGUIOpen()
             else
             {
                 if (updateEmissiveColor)
-                    UpdateEmissiveColorLDRFromIntensityAndEmissiveColor(emissiveColorLDR, emissiveIntensity, emissiveColor);
+                    UpdateEmissiveColorLDRAndIntensityFromEmissiveColor(emissiveColorLDR, emissiveIntensity, emissiveColor);
 
                 EditorGUI.BeginChangeCheck();
                 DoEmissiveTextureProperty(emissiveColorLDR);

com.unity.render-pipelines.high-definition/Runtime/Material/MaterialExtension.cs

@@ -189,19 +189,5 @@ public static void UpdateEmissiveColorFromIntensityAndEmissiveColorLDR(this Mate
                 material.SetColor(kEmissiveColor, emissiveColorLDRLinear * material.GetFloat(kEmissiveIntensity));
             }
         }
-
-        public static void UpdateEmissiveColorLDRFromIntensityAndEmissiveColor(this Material material)
-        {
-            const string kEmissiveColorLDR = "_EmissiveColorLDR";
-            const string kEmissiveColor = "_EmissiveColor";
-            const string kEmissiveIntensity = "_EmissiveIntensity";
-
-            if (material.HasProperty(kEmissiveColorLDR) && material.HasProperty(kEmissiveIntensity) && material.HasProperty(kEmissiveColor))
-            {
-                Color emissiveColorLDRLinear = material.GetColor(kEmissiveColor) / material.GetFloat(kEmissiveIntensity);
-                Color emissiveColorLDR = new Color(Mathf.LinearToGammaSpace(emissiveColorLDRLinear.r), Mathf.LinearToGammaSpace(emissiveColorLDRLinear.g), Mathf.LinearToGammaSpace(emissiveColorLDRLinear.b));
-                material.SetColor(kEmissiveColorLDR, emissiveColorLDR);
-            }
-        }
     }
 }