Decal cross fade support (#1986)

* Enable LOD cross fade

* Changelog

* Make changes only for mesh decals

* Update DecalData.hlsl

* Update DecalSurfaceOptionsUIBlock.cs

* do some cleanup and move ComputeFadeMaskSeed in ShaderVariablesFunctions.hlsl

* update documentation

* Update ShaderVariablesFunctions.hlsl

Co-authored-by: sebastienlagarde <[email protected]>

Author: FrancescoC-unity

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

@@ -131,6 +131,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - LOD meshes are now properly stripped based on the maximum lod value parameters contained in the HDRP asset.
 - Fixed an inconsistency in the LOD group UI where LOD bias was not the right one.
 - Fixed outlines in transitions between post-processed and plain regions in the graphics compositor (case 1278775).
+- Fix decal being applied twice with LOD Crossfade.
 
 ### Changed
 - Preparation pass for RTSSShadows to be supported by render graph.

com.unity.render-pipelines.high-definition/Documentation~/Master-Node-Decal.md

@@ -55,8 +55,9 @@ To view these properties, click the gear in the top right of the Master Node.
 | **Affects Ambient Occlusion** | Enable or disable the effect of the **Ambient Occlusion** property. |
 | **Affects Smoothness**        | Enable or disable the effect of the **Smoothness** property. |
 | **Affects Emission**          | Enable or disable the effect of the **Emission** property.   |
+| **Support LOD CrossFace**     | Indicates whether dithering occurs when moving from one LOD level of the receiving Mesh to another when sampling Textures. Only use with Decal Mesh. |
 | **Override ShaderGUI**        | Lets you override the [ShaderGUI](https://docs.unity3d.com/ScriptReference/ShaderGUI.html) that this Shader Graph uses. If `true`, the **ShaderGUI** property appears, which lets you specify the ShaderGUI to use. |
-| **- ShaderGUI**                 | The full name of the ShaderGUI class to use, including the class path. |
+| **- ShaderGUI**               | The full name of the ShaderGUI class to use, including the class path. |
 
 <a name="MaterialProperties"></a>
 

com.unity.render-pipelines.high-definition/Editor/Material/Decal/ShaderGraph/DecalData.cs

@@ -62,6 +62,14 @@ public int drawOrder
             set => m_DrawOrder = value;
         }
 
+        [SerializeField]
+        bool m_SupportLodCrossFade;
+        public bool supportLodCrossFade
+        {
+            get => m_SupportLodCrossFade;
+            set => m_SupportLodCrossFade = value;
+        }
+
         public bool affectsMaskmap => affectsSmoothness || affectsMetal || affectsAO;
     }
 }

com.unity.render-pipelines.high-definition/Editor/Material/Decal/ShaderGraph/DecalPass.template

@@ -97,6 +97,10 @@ Pass
             fragInputs.tangentToWorld[2].xyz = TransformObjectToWorldDir(float3(0, 1, 0));
             fragInputs.tangentToWorld[1].xyz = TransformObjectToWorldDir(float3(0, 0, 1));
         #else
+            #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
+
             float fadeFactor = 1.0;
         #endif
 

com.unity.render-pipelines.high-definition/Editor/Material/Decal/ShaderGraph/DecalPropertyBlock.cs

@@ -29,6 +29,7 @@ protected override void CreatePropertyGUI()
             AddProperty(affectAmbientOcclusionText, () => decalData.affectsAO, (newValue) => decalData.affectsAO = newValue);
             AddProperty(affectSmoothnessText, () => decalData.affectsSmoothness, (newValue) => decalData.affectsSmoothness = newValue);
             AddProperty(affectEmissionText, () => decalData.affectsEmission, (newValue) => decalData.affectsEmission = newValue);
+            AddProperty(supportLodCrossFadeText, () => decalData.supportLodCrossFade, (newValue) => decalData.supportLodCrossFade = newValue);
         }
     }
 }

com.unity.render-pipelines.high-definition/Editor/Material/Decal/ShaderGraph/DecalSubTarget.cs

@@ -70,6 +70,12 @@ protected override void CollectPassKeywords(ref PassDescriptor pass)
                 if (decalData.affectsMaskmap)
                     pass.keywords.Add(DecalDefines.Maskmap);
             }
+
+            if (pass.lightMode == DecalSystem.s_MaterialDecalPassNames[(int)DecalSystem.MaterialDecalPass.DecalMeshForwardEmissive] ||
+                pass.lightMode == DecalSystem.s_MaterialDecalPassNames[(int)DecalSystem.MaterialDecalPass.DBufferMesh])
+            {
+                pass.keywords.Add(CoreKeywordDescriptors.LodFadeCrossfade, new FieldCondition(Fields.LodCrossFade, true));
+            }
         }
 
         public static FieldDescriptor AffectsAlbedo =           new FieldDescriptor(kMaterial, "AffectsAlbedo", "");
@@ -93,6 +99,7 @@ public override void GetFields(ref TargetFieldContext context)
             context.AddField(AffectsMaskMap,       decalData.affectsMaskmap);
             context.AddField(DecalDefault,         decalData.affectsAlbedo || decalData.affectsNormal || decalData.affectsMetal ||
                                                                     decalData.affectsAO || decalData.affectsSmoothness );
+            context.AddField(Fields.LodCrossFade, decalData.supportLodCrossFade);
         }
 
         public override void GetActiveBlocks(ref TargetActiveBlockContext context)

com.unity.render-pipelines.high-definition/Editor/Material/UIBlocks/DecalSurfaceOptionsUIBlock.cs

@@ -22,6 +22,7 @@ public class Styles
             public static GUIContent affectAmbientOcclusionText = new GUIContent("Affect Ambient Occlusion", "When enabled, this decal uses the smoothness channel of its Mask Map. When disabled, the decal has no smoothness effect.");
             public static GUIContent affectSmoothnessText = new GUIContent("Affect Smoothness", "When enabled, this decal uses the ambient occlusion channel of its Mask Map. When disabled, the decal has no ambient occlusion effect.");
             public static GUIContent affectEmissionText = new GUIContent("Affect Emission", "When enabled, this decal becomes emissive and appears self-illuminated. Affect Emission does not support Affects Transparents option on Decal Projector.");
+            public static GUIContent supportLodCrossFadeText = new GUIContent("Support LOD CrossFade", "When enabled, this decal material supports LOD Cross fade if use on a Mesh.");
         }
 
         Expandable  m_ExpandableBit;

com.unity.render-pipelines.high-definition/Runtime/Material/Decal/Decal.shader

@@ -207,6 +207,9 @@ Shader "HDRP/Decal"
 			HLSLPROGRAM
 
             #pragma multi_compile DECALS_3RT DECALS_4RT
+            // enable dithering LOD crossfade
+            #pragma multi_compile _ LOD_FADE_CROSSFADE
+
 			#define SHADERPASS SHADERPASS_DBUFFER_MESH
             #include "Packages/com.unity.render-pipelines.high-definition/Runtime/ShaderLibrary/ShaderVariables.hlsl"
             #include "Packages/com.unity.render-pipelines.high-definition/Runtime/Material/Decal/DecalProperties.hlsl"
@@ -238,6 +241,8 @@ Shader "HDRP/Decal"
             Blend 0 SrcAlpha One
 
             HLSLPROGRAM
+            // enable dithering LOD crossfade
+            #pragma multi_compile _ LOD_FADE_CROSSFADE
 
             #define _MATERIAL_AFFECTS_EMISSION
             #define SHADERPASS SHADERPASS_FORWARD_EMISSIVE_MESH

com.unity.render-pipelines.high-definition/Runtime/Material/Decal/DecalData.hlsl

@@ -14,6 +14,11 @@ void GetSurfaceData(FragInputs input, float3 V, PositionInputs posInput, out Dec
     float2 offset = float2(normalToWorld[3][2], normalToWorld[3][3]);
 	float2 texCoords = input.texCoord0.xy * scale + offset;
 #elif (SHADERPASS == SHADERPASS_DBUFFER_MESH) || (SHADERPASS == SHADERPASS_FORWARD_EMISSIVE_MESH)
+
+    #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
+
 	float fadeFactor = _DecalBlend;
 	float2 texCoords = input.texCoord0.xy;
 #endif

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

@@ -125,37 +125,6 @@ void DoAlphaTest(float alpha, float alphaCutoff, out bool alphaTestResult)
 {
     alphaTestResult = alpha >= alphaCutoff;
 }
-//-----------------------------------------------------------------------------
-// LoD Fade
-//-----------------------------------------------------------------------------
-
-// Helper for LODDitheringTransition.
-uint2 ComputeFadeMaskSeed(float3 V, uint2 positionSS)
-{
-    uint2 fadeMaskSeed;
-
-    if (IsPerspectiveProjection())
-    {
-        // Start with the world-space direction V. It is independent from the orientation of the camera,
-        // and only depends on the position of the camera and the position of the fragment.
-        // Now, project and transform it into [-1, 1].
-        float2 pv = PackNormalOctQuadEncode(V);
-        // Rescale it to account for the resolution of the screen.
-        pv *= _ScreenSize.xy;
-        // The camera only sees a small portion of the sphere, limited by hFoV and vFoV.
-        // Therefore, we must rescale again (before quantization), roughly, by 1/tan(FoV/2).
-        pv *= UNITY_MATRIX_P._m00_m11;
-        // Truncate and quantize.
-        fadeMaskSeed = asuint((int2)pv);
-    }
-    else
-    {
-        // Can't use the view direction, it is the same across the entire screen.
-        fadeMaskSeed = positionSS;
-    }
-
-    return fadeMaskSeed;
-}
 
 //-----------------------------------------------------------------------------
 // Reflection / Refraction hierarchy handling