Improve transition between LOD for lit and layeredLit tessellation

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

@@ -787,6 +787,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - Pre-warm the RTHandle system to reduce the amount of memory allocations and the total memory needed at all points. 
 - DXR: Only read the geometric attributes that are required using the share pass info and shader graph defines.
 - DXR: Dispatch binned rays in 1D instead of 2D.
+- Lit and LayeredLit tessellation cross lod fade don't used dithering anymore between LOD but fade the tessellation height instead. Allow a smoother transition
 
 ## [7.1.1] - 2019-09-05
 

com.unity.render-pipelines.high-definition/Documentation~/Upgrading-from-2019.3-to-2020.1.md

@@ -2,6 +2,10 @@
 
 In the High Definition Render Pipeline (HDRP), some features work differently between major versions of Unity. This document helps you upgrade HDRP from Unity 2019.3 to 2020.1.
 
+## Mesh LOD Transition
+
+From Unity 2020.1, HDRP no longer uses dithering for the LOD crossfade transition between a LOD that uses a material with tessellation and a LOD that uses a material with no tessellation. Instead, HDRP smoothly decreases the tessellation displacement strength. This improves the transition between the first high-quality LOD with tessellation and a second mid-quality LOD without tessellation. The remaining transitions between non-tessellation materials still use dithering.
+
 ## Scene View Camera Settings
 
 From Unity 2020.1, the HDRP-specific settings of the scene view camera (anti-aliasing mode and stop NaNs) can be found in the same pop-up window as the standard scene camera settings, which are accessible by clicking the scene camera button on the toolbar of the scene window. These settings were previously in the HDRP preferences window (Edit > Preferences).

com.unity.render-pipelines.high-definition/Runtime/Material/LayeredLit/LayeredLitData.hlsl

@@ -658,7 +658,8 @@ void GetSurfaceAndBuiltinData(FragInputs input, float3 V, inout PositionInputs p
     input.texCoord1 = ((_UVMappingMask0.y + _UVMappingMask1.y + _UVMappingMask2.y + _UVMappingMask3.y + _UVDetailsMappingMask0.y + _UVDetailsMappingMask1.y + _UVDetailsMappingMask2.y + _UVDetailsMappingMask3.y) > 0) ? input.texCoord1 : 0;
 #endif
 
-#ifndef SHADER_STAGE_RAY_TRACING
+// Don't dither if displaced tessellation (we're fading out the displacement instead to match the next LOD)
+#if !defined(SHADER_STAGE_RAY_TRACING) && !defined(_TESSELLATION_DISPLACEMENT)
 #ifdef LOD_FADE_CROSSFADE // enable dithering LOD transition if user select CrossFade transition in LOD group
     LODDitheringTransition(ComputeFadeMaskSeed(V, posInput.positionSS), unity_LODFade.x);
 #endif

com.unity.render-pipelines.high-definition/Runtime/Material/LayeredLit/LayeredLitDataDisplacement.hlsl

@@ -307,6 +307,15 @@ float3 ComputePerVertexDisplacement(LayerTexCoord layerTexCoord, float4 vertexCo
     float height1 = (SAMPLE_UVMAPPING_TEXTURE2D_LOD(_HeightMap1, SAMPLER_HEIGHTMAP_IDX, layerTexCoord.base1, lod).r - _HeightCenter1) * _HeightAmplitude1;
     float height2 = (SAMPLE_UVMAPPING_TEXTURE2D_LOD(_HeightMap2, SAMPLER_HEIGHTMAP_IDX, layerTexCoord.base2, lod).r - _HeightCenter2) * _HeightAmplitude2;
     float height3 = (SAMPLE_UVMAPPING_TEXTURE2D_LOD(_HeightMap3, SAMPLER_HEIGHTMAP_IDX, layerTexCoord.base3, lod).r - _HeightCenter3) * _HeightAmplitude3;
+
+    // Scale by lod factor to ensure tessellated displacement influence is fully removed by the time we transition LODs
+#if defined(LOD_FADE_CROSSFADE) && defined(_TESSELLATION_DISPLACEMENT)
+    height0 *= unity_LODFade.x;
+    height1 *= unity_LODFade.x;
+    height2 *= unity_LODFade.x;
+    height3 *= unity_LODFade.x;
+#endif
+
     // Height is affected by tiling property and by object scale (depends on option).
     // Apply scaling from tiling properties (TexWorldScale and tiling from BaseColor)
     ApplyDisplacementTileScale(height0, height1, height2, height3);

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

@@ -186,7 +186,8 @@ void GetSurfaceAndBuiltinData(FragInputs input, float3 V, inout PositionInputs p
     input.texCoord1 = (_UVMappingMask.y + _UVDetailsMappingMask.y) > 0 ? input.texCoord1 : 0;
 #endif
 
-#if !defined(SHADER_STAGE_RAY_TRACING)
+// Don't dither if displaced tessellation (we're fading out the displacement instead to match the next LOD)
+#if !defined(SHADER_STAGE_RAY_TRACING) && !defined(_TESSELLATION_DISPLACEMENT)
 #ifdef LOD_FADE_CROSSFADE // enable dithering LOD transition if user select CrossFade transition in LOD group
     LODDitheringTransition(ComputeFadeMaskSeed(V, posInput.positionSS), unity_LODFade.x);
 #endif

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

@@ -202,6 +202,12 @@ float3 ComputePerVertexDisplacement(LayerTexCoord layerTexCoord, float4 vertexCo
 {
 #ifdef _HEIGHTMAP
     float height = (SAMPLE_UVMAPPING_TEXTURE2D_LOD(_HeightMap, sampler_HeightMap, layerTexCoord.base, lod).r - _HeightCenter) * _HeightAmplitude;
+
+    // Scale by lod factor to ensure tessellated displacement influence is fully removed by the time we transition LODs
+#if defined(LOD_FADE_CROSSFADE) && defined(_TESSELLATION_DISPLACEMENT)
+    height *= unity_LODFade.x;
+#endif
+
 #else
     float height = 0.0;
 #endif