Merge pull request #1740 from Unity-Technologies/Update-detail-map-formula

Update detail map formula

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

 
 ### Changed
 - Movde Render Pipeline Debug "Windows from Windows->General-> Render Pipeline debug windows" to "Windows from Windows->Analysis-> Render Pipeline debug windows"
+- Update detail map formula for smoothness and albedo, goal it to bright and dark perceptually and scale factor is use to control gradient speed
 
 ### Added
 - Added support for RendererPriority on Renderer. This allow to control order of transparent rendering manually. HDRP have now two stage of sorting for transparent in addition to bact to front. Material have a priority then Renderer have a priority.

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

         detailMask = SAMPLE_UVMAPPING_TEXTURE2D(ADD_IDX(_MaskMap), SAMPLER_MASKMAP_IDX, ADD_IDX(layerTexCoord.base)).b;
     #endif
     float2 detailAlbedoAndSmoothness = SAMPLE_UVMAPPING_TEXTURE2D(ADD_IDX(_DetailMap), SAMPLER_DETAILMAP_IDX, ADD_IDX(layerTexCoord.details)).rb;
-    float detailAlbedo = detailAlbedoAndSmoothness.r;
-    float detailSmoothness = detailAlbedoAndSmoothness.g;
+    float detailAlbedo = detailAlbedoAndSmoothness.r * 2.0 - 1.0;
+    float detailSmoothness = detailAlbedoAndSmoothness.g * 2.0 - 1.0;
     // Resample the detail map but this time for the normal map. This call should be optimize by the compiler
     // We split both call due to trilinear mapping
     detailNormalTS = SAMPLE_UVMAPPING_NORMALMAP_AG(ADD_IDX(_DetailMap), SAMPLER_DETAILMAP_IDX, ADD_IDX(layerTexCoord.details), ADD_IDX(_DetailNormalScale));
 #ifdef _DETAIL_MAP_IDX
-    // Use overlay blend mode for detail abledo: (base < 0.5 ? (2.0 * base * blend) : (1.0 - 2.0 * (1.0 - base) * (1.0 - blend)))
-    float3 baseColorOverlay = (detailAlbedo < 0.5) ?
-                                surfaceData.baseColor * PositivePow(2.0 * detailAlbedo, ADD_IDX(_DetailAlbedoScale)) :
-                                1.0 - (1.0 - surfaceData.baseColor) * PositivePow(2.0 * (1.0 - detailAlbedo), ADD_IDX(_DetailAlbedoScale));
+	
+	// Goal: we want the detail albedo map to be able to darken down to black and brighten up to white the surface albedo.
+	// The scale control the speed of the gradient. We simply remap detailAlbedo from [0..1] to [-1..1] then perform a lerp to black or white
+	// with a factor based on speed.
+    // For base color we interpolate in sRGB space (approximate here as square) as it get a nicer perceptual gradient
+	float albedoDetailSpeed = saturate(abs(detailAlbedo) * ADD_IDX(_DetailAlbedoScale));
+	float3 baseColorOverlay = lerp(sqrt(surfaceData.baseColor), (detailAlbedo < 0.0) ? float3(0.0, 0.0, 0.0) : float3(1.0, 1.0, 1.0), albedoDetailSpeed * albedoDetailSpeed);
+	baseColorOverlay *= baseColorOverlay;							   
     // Lerp with details mask
     surfaceData.baseColor = lerp(surfaceData.baseColor, saturate(baseColorOverlay), detailMask);
 #endif
 #endif
 
 #ifdef _DETAIL_MAP_IDX
-    // Use overlay blend mode for detail abledo: (base < 0.5 ? (2.0 * base * blend) : (1.0 - 2.0 * (1.0 - base) * (1.0 - blend)))
-    float smoothnessOverlay = (detailSmoothness < 0.5) ?
-                                surfaceData.perceptualSmoothness * PositivePow(2.0 * detailSmoothness, ADD_IDX(_DetailSmoothnessScale)) :
-                                1.0 - (1.0 - surfaceData.perceptualSmoothness) * PositivePow(2.0 * (1.0 - detailSmoothness), ADD_IDX(_DetailSmoothnessScale));
+    // See comment for baseColorOverlay
+    float smoothnessDetailSpeed = saturate(abs(detailSmoothness) * ADD_IDX(_DetailSmoothnessScale));
+	float3 smoothnessOverlay = lerp(surfaceData.perceptualSmoothness, (detailSmoothness < 0.0) ? 0.0 : 1.0, smoothnessDetailSpeed);
     // Lerp with details mask
     surfaceData.perceptualSmoothness = lerp(surfaceData.perceptualSmoothness, saturate(smoothnessOverlay), detailMask);
 #endif