Add fade distance for light impact on volumetrics (#2291)

* Fade

* changelog

* Don't display on directional

Co-authored-by: sebastienlagarde <[email protected]>

Author: FrancescoC-unity

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

@@ -10,6 +10,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - Exposed the API to access HDRP shader pass names.
 - Added the status check of default camera frame settings in the DXR wizard.
 - Added frame setting for Virtual Texturing. 
+- Added a fade distance for light influencing volumetric lighting.
 
 ### Fixed
 - Fixed a null reference exception when creating a diffusion profile asset.

com.unity.render-pipelines.high-definition/Editor/Lighting/HDLightUI.Skin.cs

@@ -103,6 +103,7 @@ sealed class Styles
             // Volumetric Additional light data
             public readonly GUIContent volumetricEnable = new GUIContent("Enable", "When enabled, this Light uses Volumetrics.");
             public readonly GUIContent volumetricDimmer = new GUIContent("Multiplier", "Controls the intensity of the scattered Volumetric lighting.");
+            public readonly GUIContent volumetricFadeDistance = new GUIContent("Fade Distance", "The distance at which light smoothly fades out from contributing to volumetric lighting.");
             // Volumetric Additional shadow data
             public readonly GUIContent volumetricShadowDimmer = new GUIContent("Shadow Dimmer", "Dims the volumetric shadows this Light casts.");
 

com.unity.render-pipelines.high-definition/Editor/Lighting/HDLightUI.cs

@@ -991,6 +991,11 @@ static void DrawVolumetric(SerializedHDLight serialized, Editor owner)
             {
                 EditorGUILayout.PropertyField(serialized.volumetricDimmer, s_Styles.volumetricDimmer);
                 EditorGUILayout.Slider(serialized.volumetricShadowDimmer, 0.0f, 1.0f, s_Styles.volumetricShadowDimmer);
+                HDLightType lightType = serialized.type;
+                if (lightType != HDLightType.Directional)
+                {
+                    EditorGUILayout.PropertyField(serialized.volumetricFadeDistance, s_Styles.volumetricFadeDistance);
+                }
             }
         }
 

com.unity.render-pipelines.high-definition/Editor/Lighting/SerializedHDLight.cs

@@ -27,6 +27,7 @@ internal class SerializedHDLight
         public SerializedProperty maxSmoothness;
         public SerializedProperty applyRangeAttenuation;
         public SerializedProperty volumetricDimmer;
+        public SerializedProperty volumetricFadeDistance;
         public SerializedProperty lightUnit;
         public SerializedProperty displayAreaLightEmissiveMesh;
         public SerializedProperty areaLightEmissiveMeshCastShadow;
@@ -336,6 +337,7 @@ public SerializedHDLight(HDAdditionalLightData[] lightDatas, LightEditor.Setting
                 spotIESCutoffPercent = o.Find("m_SpotIESCutoffPercent");
                 lightDimmer = o.Find("m_LightDimmer");
                 volumetricDimmer = o.Find("m_VolumetricDimmer");
+                volumetricFadeDistance = o.Find("m_VolumetricFadeDistance");
                 lightUnit = o.Find("m_LightUnit");
                 displayAreaLightEmissiveMesh = o.Find("m_DisplayAreaLightEmissiveMesh");
                 fadeDistance = o.Find("m_FadeDistance");

com.unity.render-pipelines.high-definition/Runtime/Lighting/Light/HDAdditionalLightData.cs

@@ -304,6 +304,24 @@ public float fadeDistance
             }
         }
 
+        // Not used for directional lights.
+        [SerializeField]
+        float m_VolumetricFadeDistance = 10000.0f;
+        /// <summary>
+        /// Get/Set the light fade distance for volumetrics.
+        /// </summary>
+        public float volumetricFadeDistance
+        {
+            get => m_VolumetricFadeDistance;
+            set
+            {
+                if (m_VolumetricFadeDistance == value)
+                    return;
+
+                m_VolumetricFadeDistance = Mathf.Clamp(value, 0, float.MaxValue);
+            }
+        }
+
         [SerializeField, FormerlySerializedAs("affectDiffuse")]
         bool m_AffectDiffuse = true;
         /// <summary>

com.unity.render-pipelines.high-definition/Runtime/Lighting/LightLoop/LightLoop.cs

@@ -259,6 +259,7 @@ internal struct ProcessedLightData
         public LightVolumeType          lightVolumeType;
         public float                    distanceToCamera;
         public float                    lightDistanceFade;
+        public float                    volumetricDistanceFade;
         public bool                     isBakedShadowMask;
     }
 
@@ -1548,7 +1549,7 @@ internal void GetLightData(CommandBuffer cmd, HDCamera hdCamera, HDShadowSetting
             lightData.lightDimmer           = processedData.lightDistanceFade * (additionalLightData.lightDimmer);
             lightData.diffuseDimmer         = processedData.lightDistanceFade * (additionalLightData.affectDiffuse  ? additionalLightData.lightDimmer : 0);
             lightData.specularDimmer        = processedData.lightDistanceFade * (additionalLightData.affectSpecular ? additionalLightData.lightDimmer * hdCamera.frameSettings.specularGlobalDimmer : 0);
-            lightData.volumetricLightDimmer = processedData.lightDistanceFade * (additionalLightData.volumetricDimmer);
+            lightData.volumetricLightDimmer = Mathf.Min(processedData.volumetricDistanceFade, processedData.lightDistanceFade) * (additionalLightData.volumetricDimmer);
 
             lightData.cookieMode = CookieMode.None;
             lightData.shadowIndex = -1;
@@ -2278,6 +2279,7 @@ void PreprocessLightData(ref ProcessedLightData processedData, VisibleLight ligh
                                                     ref processedData.lightCategory, ref processedData.gpuLightType, ref processedData.lightVolumeType);
 
             processedData.lightDistanceFade = processedData.gpuLightType == GPULightType.Directional ? 1.0f : HDUtils.ComputeLinearDistanceFade(processedData.distanceToCamera, additionalLightData.fadeDistance);
+            processedData.volumetricDistanceFade = processedData.gpuLightType == GPULightType.Directional ? 1.0f : HDUtils.ComputeLinearDistanceFade(processedData.distanceToCamera, additionalLightData.volumetricFadeDistance);
             processedData.isBakedShadowMask = IsBakedShadowMaskLight(lightComponent);
         }