Fix apply Range Attenuation

com.unity.render-pipelines.core/CoreRP/ShaderLibrary/CommonLighting.hlsl

 
 // Non physically based hack to limit light influence to attenuationRadius.
 // SmoothInfluenceAttenuation must be use, InfluenceAttenuation is just for optimization with SmoothQuadraticDistanceAttenuation
-real InfluenceAttenuation(real distSquare, real invSqrAttenuationRadius)
+real InfluenceAttenuation(real distSquare, real rangeAttenuationScale, real rangeAttenuationBias)
-    real factor = distSquare * invSqrAttenuationRadius;
-    return saturate(1.0 - factor * factor);
+    // Apply the saturate here as we can have negative number
+    real factor = saturate(distSquare * rangeAttenuationScale + rangeAttenuationBias);
+    return 1.0 - factor * factor;
-real SmoothInfluenceAttenuation(real distSquare, real invSqrAttenuationRadius)
+real SmoothInfluenceAttenuation(real distSquare, real rangeAttenuationScale, real rangeAttenuationBias)
-    real smoothFactor = InfluenceAttenuation(distSquare, invSqrAttenuationRadius);
+    real smoothFactor = InfluenceAttenuation(distSquare, rangeAttenuationScale, rangeAttenuationBias);
     return Sq(smoothFactor);
 }
 
-real SmoothQuadraticDistanceAttenuation(real distSquare, real distRcp, real invSqrAttenuationRadius)
+real SmoothQuadraticDistanceAttenuation(real distSquare, real distRcp, real rangeAttenuationScale, real rangeAttenuationBias)
-    attenuation *= InfluenceAttenuation(distSquare, invSqrAttenuationRadius);
+    attenuation *= InfluenceAttenuation(distSquare, rangeAttenuationScale, rangeAttenuationBias);
-real SmoothQuadraticDistanceAttenuation(real3 unL, real invSqrAttenuationRadius)
+real SmoothQuadraticDistanceAttenuation(real3 unL, real rangeAttenuationScale, real rangeAttenuationBias)
-    return SmoothQuadraticDistanceAttenuation(distSquare, distRcp, invSqrAttenuationRadius);
+    return SmoothQuadraticDistanceAttenuation(distSquare, distRcp, rangeAttenuationScale, rangeAttenuationBias);
 }
 
 real AngleAttenuation(real cosFwd, real lightAngleScale, real lightAngleOffset)
 
 // Combines SmoothQuadraticDistanceAttenuation() and SmoothAngleAttenuation() in an efficient manner.
 // distances = {d, d^2, 1/d, d_proj}, where d_proj = dot(lightToSample, lightData.forward).
-real SmoothPunctualLightAttenuation(real4 distances, real invSqrAttenuationRadius,
+real SmoothPunctualLightAttenuation(real4 distances, real rangeAttenuationScale, real rangeAttenuationBias,
                                      real lightAngleScale, real lightAngleOffset)
 {
     real distSq   = distances.y;
 
     real attenuation  = min(distRcp, 1.0 / PUNCTUAL_LIGHT_THRESHOLD);
-         attenuation *= InfluenceAttenuation(distSq, invSqrAttenuationRadius);
-         attenuation *= AngleAttenuation(cosFwd, lightAngleScale, lightAngleOffset);
+    attenuation *= InfluenceAttenuation(distSq, rangeAttenuationScale, rangeAttenuationBias);
+    attenuation *= AngleAttenuation(cosFwd, lightAngleScale, lightAngleOffset);
 
     return Sq(attenuation);
 }
 // The transformation is performed along the major axis of the ellipsoid (corresponding to 'r1').
 // Both the ellipsoid (e.i. 'axis') and 'unL' should be in the same coordinate system.
 // 'unL' should be computed from the center of the ellipsoid.
-real EllipsoidalDistanceAttenuation(real3 unL,  real invSqRadius,
+real EllipsoidalDistanceAttenuation(real3 unL, real rangeAttenuationScale, real rangeAttenuationBias,
                                     real3 axis, real invAspectRatio)
 {
     // Project the unnormalized light vector onto the axis.
     unL -= diff * axis;
 
     real sqDist = dot(unL, unL);
-    return SmoothInfluenceAttenuation(sqDist, invSqRadius);
+    return SmoothInfluenceAttenuation(sqDist, rangeAttenuationScale, rangeAttenuationBias);
 }
 
 // Applies SmoothInfluenceAttenuation() using the axis-aligned ellipsoid of the given dimensions.
     unL *= invHalfDim;
 
     real sqDist = dot(unL, unL);
-    return SmoothInfluenceAttenuation(sqDist, 1.0);
+    return SmoothInfluenceAttenuation(sqDist, 1.0, 0.0);
 }
 
 // Applies SmoothInfluenceAttenuation() after mapping the axis-aligned box to a sphere.
     if (Max3(abs(unL.x), abs(unL.y), abs(unL.z)) > 1.0) return 0.0;
 
     real sqDist = ComputeCubeToSphereMapSqMagnitude(unL);
-    return SmoothInfluenceAttenuation(sqDist, 1.0);
+    return SmoothInfluenceAttenuation(sqDist, 1.0, 0.0);
 }
 
 //-----------------------------------------------------------------------------

com.unity.render-pipelines.high-definition/HDRP/Lighting/LightDefinition.cs

     [GenerateHLSL]
     public struct DirectionalLightData
     {
-        public Vector3 positionWS;
-        public int tileCookie; // TODO: make it a bool
+        // Packing order depends on chronological access to avoid cache misses
+        public Vector3 positionWS;
-        public int shadowIndex; // -1 if unused
-
-        public int contactShadowIndex; // -1 if unused
-
-        public Vector3 forward;
+        public float volumetricDimmer;
-        public float specularScale;
+        public Vector3 up;      // Rescaled by (2 / shapeHeight)
+        public Vector3 forward;
+        public int tileCookie; // TODO: make it a bool
+        public int shadowIndex; // -1 if unused
+        public int contactShadowIndex; // -1 if unused
-        public Vector3 up;      // Rescaled by (2 / shapeHeight)
-        public float diffuseScale;
+        public Vector4 shadowMaskSelector; // Use with ShadowMask feature
-        public float volumetricDimmer;
-
-        public Vector4 shadowMaskSelector; // Use with ShadowMask feature
+        public float diffuseScale;
+        public float specularScale;
+        // Packing order depends on chronological access to avoid cache misses
+
-        public float invSqrAttenuationRadius;
-
-        public int shadowIndex; // -1 if unused
+        public float rangeAttenuationScale;
+        public float rangeAttenuationBias;
-        public int contactShadowIndex; // -1 if unused
-
-        public Vector3 forward;
+        public float angleScale;  // Spot light
+        public float angleOffset; // Spot light
+        public GPULightType lightType;
-        public float specularScale;
-
-        public float diffuseScale;
-
-        public float angleScale;  // Spot light
-        public float angleOffset; // Spot light
+        public Vector3 forward;
+        public int shadowIndex; // -1 if unused
+        public int contactShadowIndex; // -1 if unused
-        public int nonLightmappedOnly; // Use with ShadowMask feature // TODO: make it a bool
+        public int nonLightmappedOnly; // Use with ShadowMask feature // TODO: make it a bool      
+        public float minRoughness;  // This is use to give a small "area" to punctual light, as if we have a light with a radius.
+        public float diffuseScale;
+        public float specularScale;
-        public GPULightType lightType;
-        public float minRoughness;  // This is use to give a small "area" to punctual light, as if we have a light with a radius.
-
-        public float volumetricDimmer; // TODO: improve the cache locality
+        public float volumetricDimmer;
     };
 
 
     public struct EnvLightData
     {
         // Packing order depends on chronological access to avoid cache misses
-        // Caution: The struct need to be align on byte16 (not strictly needed for structured buffer but if we do array later better).
 
         // Proxy properties
         public Vector3 capturePositionWS;

com.unity.render-pipelines.high-definition/HDRP/Lighting/LightDefinition.cs.hlsl

 struct DirectionalLightData
 {
     float3 positionWS;
-    int tileCookie;
-    int shadowIndex;
-    int contactShadowIndex;
-    float3 forward;
+    float volumetricDimmer;
-    float specularScale;
-    float diffuseScale;
-    float volumetricDimmer;
-    int nonLightmappedOnly;
+    float3 forward;
+    int tileCookie;
+    int shadowIndex;
+    int contactShadowIndex;
+    int nonLightmappedOnly;
+    float diffuseScale;
+    float specularScale;
 };
 
 // Generated from UnityEngine.Experimental.Rendering.HDPipeline.LightData
     float3 positionWS;
-    float invSqrAttenuationRadius;
-    int shadowIndex;
-    int contactShadowIndex;
-    float3 forward;
+    float rangeAttenuationScale;
+    float rangeAttenuationBias;
+    float angleScale;
+    float angleOffset;
+    int lightType;
-    float specularScale;
-    float diffuseScale;
-    float angleScale;
-    float angleOffset;
+    float3 forward;
+    int shadowIndex;
+    int contactShadowIndex;
+    float4 shadowMaskSelector;
-    float4 shadowMaskSelector;
-    float2 size;
-    int lightType;
+    float diffuseScale;
+    float specularScale;
+    float2 size;
     float volumetricDimmer;
 };
 
 {
     return value.positionWS;
 }
-int GetTileCookie(DirectionalLightData value)
-{
-    return value.tileCookie;
-}
-int GetShadowIndex(DirectionalLightData value)
+int GetCookieIndex(DirectionalLightData value)
-    return value.shadowIndex;
+    return value.cookieIndex;
-int GetContactShadowIndex(DirectionalLightData value)
+float GetVolumetricDimmer(DirectionalLightData value)
-    return value.contactShadowIndex;
+    return value.volumetricDimmer;
-float3 GetForward(DirectionalLightData value)
+float3 GetRight(DirectionalLightData value)
-    return value.forward;
+    return value.right;
-int GetCookieIndex(DirectionalLightData value)
+float3 GetUp(DirectionalLightData value)
-    return value.cookieIndex;
+    return value.up;
-float3 GetRight(DirectionalLightData value)
+float3 GetForward(DirectionalLightData value)
-    return value.right;
+    return value.forward;
-float GetSpecularScale(DirectionalLightData value)
+int GetTileCookie(DirectionalLightData value)
-    return value.specularScale;
+    return value.tileCookie;
-float3 GetUp(DirectionalLightData value)
+int GetShadowIndex(DirectionalLightData value)
-    return value.up;
+    return value.shadowIndex;
-float GetDiffuseScale(DirectionalLightData value)
+int GetContactShadowIndex(DirectionalLightData value)
-    return value.diffuseScale;
+    return value.contactShadowIndex;
-float GetVolumetricDimmer(DirectionalLightData value)
+float4 GetShadowMaskSelector(DirectionalLightData value)
-    return value.volumetricDimmer;
+    return value.shadowMaskSelector;
-float4 GetShadowMaskSelector(DirectionalLightData value)
+float GetDiffuseScale(DirectionalLightData value)
+{
+    return value.diffuseScale;
+}
+float GetSpecularScale(DirectionalLightData value)
-    return value.shadowMaskSelector;
+    return value.specularScale;
 }
 
 //
 {
     return value.positionWS;
 }
-float GetInvSqrAttenuationRadius(LightData value)
+float3 GetColor(LightData value)
-    return value.invSqrAttenuationRadius;
+    return value.color;
-float3 GetColor(LightData value)
+float GetRangeAttenuationScale(LightData value)
-    return value.color;
+    return value.rangeAttenuationScale;
-int GetShadowIndex(LightData value)
+float GetRangeAttenuationBias(LightData value)
-    return value.shadowIndex;
+    return value.rangeAttenuationBias;
-int GetContactShadowIndex(LightData value)
+float GetAngleScale(LightData value)
-    return value.contactShadowIndex;
+    return value.angleScale;
-float3 GetForward(LightData value)
+float GetAngleOffset(LightData value)
-    return value.forward;
+    return value.angleOffset;
+}
+int GetLightType(LightData value)
+{
+    return value.lightType;
-float GetSpecularScale(LightData value)
-{
-    return value.specularScale;
-}
-float GetDiffuseScale(LightData value)
+float3 GetForward(LightData value)
-    return value.diffuseScale;
+    return value.forward;
-float GetAngleScale(LightData value)
+int GetShadowIndex(LightData value)
-    return value.angleScale;
+    return value.shadowIndex;
-float GetAngleOffset(LightData value)
+int GetContactShadowIndex(LightData value)
-    return value.angleOffset;
+    return value.contactShadowIndex;
+float4 GetShadowMaskSelector(LightData value)
+{
+    return value.shadowMaskSelector;
+}
-float4 GetShadowMaskSelector(LightData value)
+float GetMinRoughness(LightData value)
-    return value.shadowMaskSelector;
+    return value.minRoughness;
-float2 GetSize(LightData value)
+float GetDiffuseScale(LightData value)
-    return value.size;
+    return value.diffuseScale;
-int GetLightType(LightData value)
+float GetSpecularScale(LightData value)
-    return value.lightType;
+    return value.specularScale;
-float GetMinRoughness(LightData value)
+float2 GetSize(LightData value)
-    return value.minRoughness;
+    return value.size;
 }
 float GetVolumetricDimmer(LightData value)
 {

com.unity.render-pipelines.high-definition/HDRP/Lighting/LightEvaluation.hlsl

     float  shadowMask    = 1.0;
 
     color       = lightData.color;
-    attenuation = SmoothPunctualLightAttenuation(distances, lightData.invSqrAttenuationRadius,
+    attenuation = SmoothPunctualLightAttenuation(distances, lightData.rangeAttenuationScale, lightData.rangeAttenuationBias,
                                                  lightData.angleScale, lightData.angleOffset);
 
 #if (SHADEROPTIONS_VOLUMETRIC_LIGHTING_PRESET != 0)

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

             lightData.lightType = gpuLightType;
 
             lightData.positionWS = light.light.transform.position;
-            // Setting 0 for invSqrAttenuationRadius mean we have no range attenuation, but still have inverse square attenuation.
+
-            lightData.invSqrAttenuationRadius = applyRangeAttenuation ? 1.0f / (light.range * light.range) : 0.0f;
+
+            // In the shader we do range remapping: (x - start) / (end - start) = (dist^2 * rangeAttenuationScale + rangeAttenuationBias)
+            if (applyRangeAttenuation)
+            {
+                // start = 0.0f, end = range^2
+                lightData.rangeAttenuationScale = 1.0f / (light.range * light.range);
+                lightData.rangeAttenuationBias = 0.0f;
+            }
+            else // Don't apply any attenuation but do a 'step' at range
+            {
+                // start = range^2 - epsilon, end = range^2
+                lightData.rangeAttenuationScale = 1.0f / 0.01f;
+                lightData.rangeAttenuationBias = - (light.range * light.range - 0.01f) / 0.01f;
+            }
+
             lightData.color = GetLightColor(light);
 
             lightData.forward = light.light.transform.forward; // Note: Light direction is oriented backward (-Z)

com.unity.render-pipelines.high-definition/HDRP/Material/Lit/Lit.hlsl

 
     // We define the ellipsoid s.t. r1 = (r + len / 2), r2 = r3 = r.
     // TODO: This could be precomputed.
-    float radius         = rsqrt(lightData.invSqrAttenuationRadius);
+    float radius         = rsqrt(lightData.rangeAttenuationScale); //  // rangeAttenuationScale is inverse Square Radius
-    float intensity = EllipsoidalDistanceAttenuation(unL, lightData.invSqrAttenuationRadius,
+    float intensity = EllipsoidalDistanceAttenuation(unL, lightData.rangeAttenuationScale, lightData.rangeAttenuationBias,
                                                      axis, invAspectRatio);
 
     // Terminate if the shaded point is too far away.
 
     // Define the dimensions of the attenuation volume.
     // TODO: This could be precomputed.
-    float  radius     = rsqrt(lightData.invSqrAttenuationRadius);
+    float  radius     = rsqrt(lightData.rangeAttenuationScale); // rangeAttenuationScale is inverse Square Radius
     float3 invHalfDim = rcp(float3(radius + halfWidth,
                                    radius + halfHeight,
                                    radius));