Added a directionality parameter to the wind vertex animation.

Assets/ScriptableRenderPipeline/HDRenderPipeline/Material/LayeredLit/LayeredLit.shader

         _Stiffness("Stiffness", float) = 1.0
         _Drag("Drag", float) = 1.0
         _ShiverDrag("Shiver Drag", float) = 0.2
+        _ShiverDirectionality("Shiver Directionality", Range(0.0, 1.0)) = 0.5
 
         _EmissiveColor("EmissiveColor", Color) = (0, 0, 0)
         _EmissiveColorMap("EmissiveColorMap", 2D) = "white" {}

Assets/ScriptableRenderPipeline/HDRenderPipeline/Material/LayeredLit/LayeredLitTessellation.shader

         _Stiffness("Stiffness", float) = 1.0
         _Drag("Drag", float) = 1.0
         _ShiverDrag("Shiver Drag", float) = 0.2
+        _ShiverDirectionality("Shiver Directionality", Range(0.0, 1.0)) = 0.5
 
         _EmissiveColor("EmissiveColor", Color) = (0, 0, 0)
         _EmissiveColorMap("EmissiveColorMap", 2D) = "white" {}

Assets/ScriptableRenderPipeline/HDRenderPipeline/Material/Lit/Editor/BaseLitUI.cs

             public static GUIContent windStiffnessText = new GUIContent("Stiffness");
             public static GUIContent windDragText = new GUIContent("Drag");
             public static GUIContent windShiverDragText = new GUIContent("Shiver Drag");
+            public static GUIContent windShiverDirectionalityText = new GUIContent("Shiver Directionality");
 
             public static string vertexAnimation = "Vertex Animation";
         }
         protected const string kWindDrag = "_Drag";
         protected MaterialProperty windShiverDrag = null;
         protected const string kWindShiverDrag = "_ShiverDrag";
+        protected MaterialProperty windShiverDirectionality = null;
+        protected const string kWindShiverDirectionality = "_ShiverDirectionality";
 
         // Per pixel displacement params
         protected MaterialProperty enablePerPixelDisplacement = null;
             windStiffness = FindProperty(kWindStiffness, props);
             windDrag = FindProperty(kWindDrag, props);
             windShiverDrag = FindProperty(kWindShiverDrag, props);
+            windShiverDirectionality = FindProperty(kWindShiverDirectionality, props);
         }
 
         void TessellationModePopup()
                 m_MaterialEditor.ShaderProperty(windStiffness, StylesBaseLit.windStiffnessText);
                 m_MaterialEditor.ShaderProperty(windDrag, StylesBaseLit.windDragText);
                 m_MaterialEditor.ShaderProperty(windShiverDrag, StylesBaseLit.windShiverDragText);
+                m_MaterialEditor.ShaderProperty(windShiverDirectionality, StylesBaseLit.windShiverDirectionalityText);
                 EditorGUI.indentLevel--;
             }
 

Assets/ScriptableRenderPipeline/HDRenderPipeline/Material/Lit/Lit.shader

         _Stiffness("Stiffness", float) = 1.0
         _Drag("Drag", float) = 1.0
         _ShiverDrag("Shiver Drag", float) = 0.2
+        _ShiverDirectionality("Shiver Directionality", Range(0.0, 1.0)) = 0.5
 
         //_CoatCoverage("CoatCoverage", Range(0.0, 1.0)) = 0
         //_CoatCoverageMap("CoatCoverageMapMap", 2D) = "white" {}

Assets/ScriptableRenderPipeline/HDRenderPipeline/Material/Lit/LitProperties.hlsl

 float _Stiffness;
 float _Drag;
 float _ShiverDrag;
+float _ShiverDirectionality;
 
 #ifndef LAYERED_LIT_SHADER
 

Assets/ScriptableRenderPipeline/HDRenderPipeline/Material/Lit/LitTessellation.shader

         _Stiffness("Stiffness", float) = 1.0
         _Drag("Drag", float) = 1.0
         _ShiverDrag("Shiver Drag", float) = 0.2
+        _ShiverDirectionality("Shiver Directionality", Range(0.0, 1.0)) = 0.5
 
         //_CoatCoverage("CoatCoverage", Range(0.0, 1.0)) = 0
         //_CoatCoverageMap("CoatCoverageMapMap", 2D) = "white" {}

Assets/ScriptableRenderPipeline/HDRenderPipeline/ShaderPass/VertMesh.hlsl

 
 #if _VERTEX_WIND
     float3 rootWP = mul(GetObjectToWorldMatrix(), float4(0, 0, 0, 1)).xyz;
-    ApplyWind(positionWS, normalWS, rootWP, _Stiffness, _Drag, _ShiverDrag, _InitialBend, vertexColor.a, _Time);
+    ApplyWind(positionWS, normalWS, rootWP, _Stiffness, _Drag, _ShiverDrag, _ShiverDirectionality, _InitialBend, vertexColor.a, _Time);
 #endif
 
 #ifdef TESSELLATION_ON

Assets/ScriptableRenderPipeline/ShaderLibrary/Wind.hlsl

     float3 Direction;
     float Strength;
     float3 ShiverStrength;
+    float3 ShiverDirection;
 };
 
 
     float shiver = length(shiverNoise);
 
     result.Direction = dir;
+    result.ShiverDirection = shiverNoise;
-    result.ShiverStrength = shiver;
+    result.ShiverStrength = shiver + shiver * gust;
 
     return result;
 }
-void ApplyWind(inout float3 worldPos, inout float3 worldNormal, float3 rootWP, float stiffness, float drag, float shiverDrag, float initialBend, float shiverMask, float4 time)
+void ApplyWind( inout float3    worldPos, 
+                inout float3    worldNormal,
+                float3          rootWP,
+                float           stiffness,
+                float           drag,
+                float           shiverDrag,
+                float           shiverDirectionality,
+                float           initialBend,
+                float           shiverMask,
+                float4          time)
 {
     WindData wind = GetAnalyticalWind(worldPos, rootWP, drag, shiverDrag, initialBend, time);
 
         float3 rotAxis = cross(float3(0, 1, 0), wind.Direction);
 
         worldPos = Rotate(rootWP, worldPos, rotAxis, (wind.Strength) * 0.001 * att);
-        worldPos += wind.ShiverStrength * worldNormal * shiverMask;
+        
+        float3 shiverDirection = normalize(lerp(worldNormal, normalize(wind.Direction + wind.ShiverDirection), shiverDirectionality));
+        worldPos += wind.ShiverStrength * shiverDirection * shiverMask;
     }
 
 }