HDRenderPipeline: Remove unused code

ScriptableRenderPipeline/Core/ShaderLibrary/Refraction.hlsl

 
 struct RefractionModelResult
 {
-    float       opticalDepth;
+    float       distance;       // length of the transmission during refraction through the shape
     float3      positionWS;     // out ray position
     float3      rayWS;          // out ray direction
 };
     // Second refraction (tangent sphere out)
     float NoR1 = dot(normalWS, R1);
     // Optical depth within the sphere
-    float opticalDepth = -NoR1 * thickness;
+    float distance = -NoR1 * thickness;
-    float3 P1 = positionWS + R1 * opticalDepth;
+    float3 P1 = positionWS + R1 * distance;
     // Out normal
     float3 N1 = normalize(C - P1);
     // Out refracted ray
 
     RefractionModelResult result;
-    result.opticalDepth = opticalDepth;
+    result.distance = distance;
     result.positionWS = P1;
     result.rayWS = R2;
 
     float3 R = refract(-V, normalWS, 1.0 / ior);
 
     // Optical depth within the thin plane
-    float opticalDepth = thickness / dot(R, -normalWS);
+    float distance = thickness / dot(R, -normalWS);
-    result.opticalDepth = opticalDepth;
-    result.positionWS = positionWS + R * opticalDepth;
+    result.distance = distance;
+    result.positionWS = positionWS + R * distance;
     result.rayWS = -V;
 
     return result;

ScriptableRenderPipeline/HDRenderPipeline/Material/Lit/Lit.hlsl

     // Refraction
     float3 transmissionRefractV;            // refracted view vector after exiting the shape
     float3 transmissionPositionWS;          // start of the refracted ray after exiting the shape
-    float transmissionOpticalDepth;         // length of the transmission during refraction through the shape
     float3 transmissionTransmittance;       // transmittance due to absorption
     float transmissionSSMipLevel;           // mip level of the screen space gaussian pyramid for rough refraction
 
 };
 
-// This is a refract - TODO: do we call original refract or this one, original maybe slightly emore expensive, to check
+// This is a refract - TODO: do we call original refract or this one, original maybe slightly more expensive, to check
 float3 ClearCoatTransform(float3 X, float3 N, float ieta)
 {
     float XdotN = saturate(dot(N, X));
     RefractionModelResult refraction = REFRACTION_MODEL(V, posInput, bsdfData);
     preLightData.transmissionRefractV = refraction.rayWS;
     preLightData.transmissionPositionWS = refraction.positionWS;
-    preLightData.transmissionOpticalDepth = refraction.opticalDepth;
-    preLightData.transmissionTransmittance = exp(-bsdfData.absorptionCoefficient * refraction.opticalDepth);
+    preLightData.transmissionTransmittance = exp(-bsdfData.absorptionCoefficient * refraction.distance);
-    preLightData.transmissionOpticalDepth = 0;
     preLightData.transmissionTransmittance = float3(1.0, 1.0, 1.0);
     preLightData.transmissionSSMipLevel = 0;
 #endif