Use correct sampler for refraction, refactored PerceptualRoughnessToMipmapLevel

ScriptableRenderPipeline/Core/ShaderLibrary/ImageBasedLighting.hlsl

 // approximating the cone of the specular lobe, and then computing the MIP map level
 // which (approximately) covers the footprint of the lobe with a single texel.
 // Improves the perceptual roughness distribution.
-float PerceptualRoughnessToMipmapLevel(float perceptualRoughness)
+float PerceptualRoughnessToMipmapLevel(float perceptualRoughness, uint mipMapCount)
-    return perceptualRoughness * UNITY_SPECCUBE_LOD_STEPS;
+    return perceptualRoughness * mipMapCount;
+}
+
+float PerceptualRoughnessToMipmapLevel(float perceptualRoughness)
+{
+    return PerceptualRoughnessToMipmapLevel(perceptualRoughness, UNITY_SPECCUBE_LOD_STEPS);
 }
 
 // The *accurate* version of the non-linear remapping. It works by

ScriptableRenderPipeline/HDRenderPipeline/Material/Lit/Lit.hlsl

 // Color pyramid (width, height, lodcount, Unused)
 float4 _GaussianPyramidColorMipSize;
 TEXTURE2D(_GaussianPyramidColorTexture);
-SAMPLER2D(sampler_GaussianPyramidColorTexture);
 
 // Depth pyramid (width, height, lodcount, Unused)
 float4 _PyramidDepthMipSize;
 SamplerState ltc_linear_clamp_sampler;
+SamplerState ltc_trilinear_clamp_sampler;
 // TODO: This one should be set into a constant Buffer at pass frequency (with _Screensize)
 TEXTURE2D(_PreIntegratedFGD);
 TEXTURE2D_ARRAY(_LtcData); // We pack the 3 Ltc data inside a texture array
 // EvaluateBSDF_SSL
 // ----------------------------------------------------------------------------
 
-float PerceptualRoughnessToMipmapLevel(float perceptualRoughness, uint mipMapCount)
-{
-    perceptualRoughness = perceptualRoughness * (1.7 - 0.7 * perceptualRoughness);
-
-    return perceptualRoughness * mipMapCount;
-}
-
 void EvaluateBSDF_SSL(float3 V, PositionInputs posInput, BSDFData bsdfData, out float3 diffuseLighting, out float3 specularLighting, out float2 weight)
 {
     diffuseLighting = float3(0.0, 0.0, 0.0);
         || any(refractedBackPointSS < 0.0)
         || any(refractedBackPointSS > 1.0))
     {
-        diffuseLighting = SAMPLE_TEXTURE2D_LOD(_GaussianPyramidColorTexture, sampler_GaussianPyramidColorTexture, posInput.positionSS, 0.0).rgb;
+        diffuseLighting = SAMPLE_TEXTURE2D_LOD(_GaussianPyramidColorTexture, ltc_trilinear_clamp_sampler, posInput.positionSS, 0.0).rgb;
-    diffuseLighting = SAMPLE_TEXTURE2D_LOD(_GaussianPyramidColorTexture, sampler_GaussianPyramidColorTexture, refractedBackPointSS, mipLevel).rgb;
+    diffuseLighting = SAMPLE_TEXTURE2D_LOD(_GaussianPyramidColorTexture, ltc_trilinear_clamp_sampler, refractedBackPointSS, mipLevel).rgb;
 
     // Beer-Lamber law for absorption
     float3 transmittance = exp(-bsdfData.absorptionCoefficient * opticalDepth);
     // Use perfect flat transparency when we cannot fetch the correct pixel color for the refracted point
-    diffuseLighting = SAMPLE_TEXTURE2D_LOD(_GaussianPyramidColorTexture, sampler_GaussianPyramidColorTexture, posInput.positionSS, 0.0).rgb;
+    diffuseLighting = SAMPLE_TEXTURE2D_LOD(_GaussianPyramidColorTexture, ltc_trilinear_clamp_sampler, posInput.positionSS, 0.0).rgb;
 #endif
 }