Apply thickness bias in world space

Assets/ScriptableRenderPipeline/HDRenderPipeline/Lighting/TilePass/TilePass.hlsl

 // Shadow sampling function
 // ----------------------------------------------------------------------------
 
-float GetPunctualShadowAttenuation(LightLoopContext lightLoopContext, uint lightType, float3 positionWS, int index, float3 L, float2 unPositionSS, float bias)
+float GetPunctualShadowAttenuation(LightLoopContext lightLoopContext, uint lightType, float3 positionWS, int index, float3 L, float2 unPositionSS)
 {
     int faceIndex = 0;
     if (lightType == GPULIGHTTYPE_POINT)
     float4 positionTXS = mul(float4(positionWS, 1.0), shadowData.worldToShadow);
     positionTXS.xyz /= positionTXS.w;
     // positionTXS.z -=  shadowData.bias;
-    positionTXS.z -= (bias + 0.001); // Apply a linear bias
+    positionTXS.z -= 0.001; // Apply a linear bias
 
 #if UNITY_REVERSED_Z
     positionTXS.z = 1.0 - positionTXS.z;
     return int(4.0 - dot(weights, float4(4.0, 3.0, 2.0, 1.0)));
 }
 
-float GetDirectionalShadowAttenuation(LightLoopContext lightLoopContext, float3 positionWS, int index, float3 L, float2 unPositionSS, float bias)
+float GetDirectionalShadowAttenuation(LightLoopContext lightLoopContext, float3 positionWS, int index, float3 L, float2 unPositionSS)
 {
     // Note Index is 0 for now, but else we need to provide the correct index in _DirShadowSplitSpheres and _ShadowDatas
     int shadowSplitIndex = GetSplitSphereIndexForDirshadows(positionWS, _DirShadowSplitSpheres);
     float4 positionTXS = mul(float4(positionWS, 1.0), shadowData.worldToShadow);
     positionTXS.xyz /= positionTXS.w;
     // positionTXS.z -=  shadowData.bias;
-    positionTXS.z -= (bias + 0.003); // Apply a linear bias
+    positionTXS.z -= 0.003; // Apply a linear bias
 
 #if UNITY_REVERSED_Z
     positionTXS.z = 1.0 - positionTXS.z;

Assets/ScriptableRenderPipeline/HDRenderPipeline/Material/Lit/Lit.hlsl

 #ifdef HAS_LIGHTLOOP
 
 //-----------------------------------------------------------------------------
-// BSDF share between directional light, punctual light and area light (reference) 
+// BSDF share between directional light, punctual light and area light (reference)
 //-----------------------------------------------------------------------------
 
 void BSDF(  float3 V, float3 L, float3 positionWS, PreLightData preLightData, BSDFData bsdfData,
 
     [branch] if (lightData.shadowIndex >= 0 && illuminance > 0.0)
     {
-        float shadow = GetDirectionalShadowAttenuation(lightLoopContext, positionWS, lightData.shadowIndex, L, posInput.unPositionSS, 0);
+        float shadow = GetDirectionalShadowAttenuation(lightLoopContext, positionWS, lightData.shadowIndex, L, posInput.unPositionSS);
 
         illuminance *= shadow;
     }
 
         [branch] if (lightData.shadowIndex >= 0 && illuminance > 0.0)
         {
-            float shadow = GetDirectionalShadowAttenuation(lightLoopContext, positionWS, lightData.shadowIndex, L, posInput.unPositionSS, bsdfData.thickness);
+            // TODO: factor out the biased position?
+            float3 biasedPositionWS = positionWS + bsdfData.normalWS * bsdfData.thickness;
+            float shadow = GetDirectionalShadowAttenuation(lightLoopContext, biasedPositionWS, lightData.shadowIndex, L, posInput.unPositionSS);
             illuminance *= shadow;
         }
 
     [branch] if (lightData.shadowIndex >= 0 && illuminance > 0.0)
     {
         float3 offset = float3(0.0, 0.0, 0.0); // GetShadowPosOffset(nDotL, normal);
-        float  shadow = GetPunctualShadowAttenuation(lightLoopContext, lightData.lightType, positionWS + offset, lightData.shadowIndex, L, posInput.unPositionSS, 0);
+        float  shadow = GetPunctualShadowAttenuation(lightLoopContext, lightData.lightType, positionWS + offset, lightData.shadowIndex, L, posInput.unPositionSS);
         shadow = lerp(1.0, shadow, lightData.shadowDimmer);
 
         illuminance *= shadow;
 
         [branch] if (lightData.shadowIndex >= 0 && illuminance > 0.0)
         {
+            // TODO: factor out the common biased position?
+            float3 biasedPositionWS = positionWS + bsdfData.normalWS * bsdfData.thickness;
-            float  shadow = GetPunctualShadowAttenuation(lightLoopContext, lightData.lightType, positionWS + offset, lightData.shadowIndex, L, posInput.unPositionSS, bsdfData.thickness);
+            float  shadow = GetPunctualShadowAttenuation(lightLoopContext, lightData.lightType, biasedPositionWS + offset, lightData.shadowIndex, L, posInput.unPositionSS);
             shadow = lerp(1.0, shadow, lightData.shadowDimmer);
 
             illuminance *= shadow;