Merge pull request #1729 from Unity-Technologies/HDRP/decals/v2_1/depth_bias

Hdrp/decals/v2 1/depth bias

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

 
 ### Added
 - Decal now support per channel selection mask. There is now two mode. One with BaseColor, Normal and Smoothness and another one more expensive with BaseColor, Normal, Smoothness, Metal and AO. Control is on HDRP Asset. This may require to launch an update script for old scene: 'Edit/Render Pipeline/Single step upgrade script/Upgrade all DecalMaterial MaskBlendMode'.
+- Decal now supports depth bias for decal mesh, to prevent z-fighting
 
 ### Fixed
 - Fixed an issue with PreIntegratedFGD texture being sometimes destroyed and not regenerated causing rendering to break

com.unity.render-pipelines.high-definition/HDRP/Editor/Material/Decal/DecalUI.cs

             public static GUIContent normalMapText = new GUIContent("Normal Map", "Normal Map (BC7/BC5/DXT5(nm))");
             public static GUIContent decalBlendText = new GUIContent("Global Opacity", "Whole decal Opacity");
             public static GUIContent AlbedoModeText = new GUIContent("Affect BaseColor", "Base color + Opacity, Opacity only");
+ 			public static GUIContent MeshDecalDepthBiasText = new GUIContent("Mesh decal depth bias", "prevents z-fighting");
 
             public static GUIContent[] maskMapText =
             {
         protected MaterialProperty maskmapSmoothness = new MaterialProperty();
         protected const string kMaskmapSmoothness = "_MaskmapSmoothness";
 
+        protected MaterialProperty decalMeshDepthBias = new MaterialProperty();
+        protected const string kDecalMeshDepthBias = "_DecalMeshDepthBias";
+
         protected MaterialEditor m_MaterialEditor;
 
         // This is call by the inspector
             maskmapMetal = FindProperty(kMaskmapMetal, props);
             maskmapAO = FindProperty(kMaskmapAO, props);
             maskmapSmoothness = FindProperty(kMaskmapSmoothness, props);
+            decalMeshDepthBias = FindProperty(kDecalMeshDepthBias, props);
             
             // always instanced
             SerializedProperty instancing = m_MaterialEditor.serializedObject.FindProperty("m_EnableInstancingVariants");
                     EditorGUI.indentLevel--;
                 }
                 m_MaterialEditor.ShaderProperty(decalBlend, Styles.decalBlendText);
+                m_MaterialEditor.ShaderProperty(decalMeshDepthBias, Styles.MeshDecalDepthBiasText);
                 EditorGUI.indentLevel--;
 
                 EditorGUILayout.HelpBox(

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

 		[ToggleUI] _MaskmapMetal("_MaskmapMetal", Range(0.0, 1.0)) = 0.0
 		[ToggleUI] _MaskmapAO("_MaskmapAO", Range(0.0, 1.0)) = 0.0
 		[ToggleUI] _MaskmapSmoothness("_MaskmapSmoothness", Range(0.0, 1.0)) = 1.0
+		[HideInInspector] _DecalMeshDepthBias("_DecalMeshDepthBias", Float) = 0.0 
     }
 
     HLSLINCLUDE

com.unity.render-pipelines.high-definition/HDRP/Material/Decal/DecalProperties.hlsl

 
 float _DecalBlend;
 float4 _BaseColor;
+float _DecalMeshDepthBias;
 
 #endif

com.unity.render-pipelines.high-definition/HDRP/ShaderPass/ShaderPassDBuffer.hlsl

 #include "VertMesh.hlsl"
 
 
+void MeshDecalsPositionZBias(inout VaryingsToPS input)
+{
+#if defined(UNITY_REVERSED_Z)
+	input.vmesh.positionCS.z -= _DecalMeshDepthBias * input.vmesh.positionCS.w;
+#else
+	input.vmesh.positionCS.z += _DecalMeshDepthBias * input.vmesh.positionCS.w;
+#endif
+}
+
+#if (SHADERPASS == SHADERPASS_DBUFFER_MESH)
+	MeshDecalsPositionZBias(varyingsType);
+#endif
     return PackVaryingsType(varyingsType);
 }