how to animated wind effect shader only this portion of vertices not bottom

``````// Author: https://discussions.unity.com/t/678713
// Source: https://en.wikibooks.org/wiki/Cg_Programming/Unity/Billboards
// Source: http://www.unity3d-france.com/unity/phpBB3/viewtopic.php?t=12304
{
Properties
{
_MainTex ("Texture Image", 2D) = "white" {}
_Cutoff ("Alpha cutoff", Range(0,1)) = 0.5
_ScaleX ("Scale X", Float) = 1.0
_ScaleY ("Scale Y", Float) = 1.0
}
{
Cull Off
Pass
{
CGPROGRAM
#include "UnityCG.cginc"
#pragma vertex vert
#pragma fragment frag
// User-specified uniforms
uniform sampler2D _MainTex;
uniform float _ScaleX;
uniform float _ScaleY;

float4 _MainTex_ST;
fixed _Cutoff;
struct vertexInput
{
float4 vertex : POSITION;
float4 tex : TEXCOORD0;
};
struct vertexOutput
{
float4 pos : SV_POSITION;
float2 tex : TEXCOORD0;
};
vertexOutput vert(vertexInput input)
{
// The world position of the center of the object
float3 worldPos = mul(unity_ObjectToWorld, float4(0, 0, 0, 1)).xyz;
// Distance between the camera and the center
float3 dist = _WorldSpaceCameraPos - worldPos;
// atan2(dist.x, dist.z) = atan (dist.x / dist.z)
// With atan the tree inverts when the camera has the same z position
float angle = atan2(dist.x, dist.z);
float3x3 rotMatrix;
float cosinus = cos(angle);
float sinus = sin(angle);

// Rotation matrix in Y
rotMatrix[0].xyz = float3(cosinus, 0, sinus);
rotMatrix[1].xyz = float3(0, 1, 0);
rotMatrix[2].xyz = float3(- sinus, 0, cosinus);
// The position of the vertex after the rotation
float4 newPos = float4(mul(rotMatrix, input.vertex * float4(_ScaleX, _ScaleY, 0, 0)), 1);
// The model matrix without the rotation and scale
float4x4 matrix_M_noRot = unity_ObjectToWorld;
matrix_M_noRot[0][0] = 1;
matrix_M_noRot[0][1] = 0;
matrix_M_noRot[0][2] = 0;
matrix_M_noRot[1][0] = 0;
matrix_M_noRot[1][1] = 1;
matrix_M_noRot[1][2] = 0;
matrix_M_noRot[2][0] = 0;
matrix_M_noRot[2][1] = 0;
matrix_M_noRot[2][2] = 1;
vertexOutput output;
// The position of the vertex in clip space ignoring the rotation and scale of the object
#if IGNORE_ROTATION_AND_SCALE
output.pos = mul(UNITY_MATRIX_VP, mul(matrix_M_noRot, newPos));
#else
output.pos = mul(UNITY_MATRIX_VP, mul(unity_ObjectToWorld, newPos));
#endif
output.tex = TRANSFORM_TEX(input.tex, _MainTex);
return output;
}

float4 frag(vertexOutput input) : COLOR
{
fixed4 col = tex2D(_MainTex, float2(input.tex.xy));
clip(col.a - _Cutoff);
return col;
}
ENDCG
}
}
}
``````

Ok, guess ill be the first to say this, lol. Why would you want a billboard to have wind effects?, that a performance killerâ€¦ Wind should only effect the other LODs, not the billboard.