Shadow implementation of unity vertex animation

Shader "Custom/Chapter11-Billboard" {
    
	Properties
	{
    
		_MainTex("Main Tex",2D) = "White"{
    }
		_Color("Color Tint",Color) = (1,1,1,1)
		_VerticalBillboarding("Vertical Restraints",Range(0,1)) = 1
	}
	
	SubShader
	{
    
		Tags {
    "Queue" = "Transparent" "IgnoreProjector" = "True" "RenderType" = "Transparent" "DisableBatching" = "True"}
		pass
		{
    
			Tags {
    "LightMode" = "ForwardBase"}

			ZWrite off
			Blend SrcAlpha OneMinusSrcAlpha
			Cull off

			CGPROGRAM
			#pragma vertex vert
			#pragma fragment frag
			#include "Lighting.cginc"
			#include "unityCG.cginc"

			sampler2D _MainTex;
			float4 _MainTex_ST;
			fixed4 _Color;
			fixed _VerticalBillboarding;

			struct a2v
			{
    
				float4 vertex :POSITION;
				float4 texcoord:TEXCOORD0;
			};
			struct v2f
			{
    
				float4 pos:SV_POSITION;
				float2 uv:TEXCOORD0;
				//V2F_SHADOW_CASTER;
			};

			v2f vert(a2v v)
			{
    
				v2f o;
				float3 center = float3(0,0,0);// Set the anchor of the billboard 
				float3 viewer =mul(_World2Object,float4(_WorldSpaceCameraPos,1));// Obtain the view coordinates in the model space 
				float3 normalDir = viewer-center;// According to the angle of view and the position of the anchor , Calculate the target normal direction 

				float3 upDir = abs(normalDir.y>0.999?float3(0,0,1):float3(0,1,0));// Calculate the upward direction , The premise is that it is not parallel to the normal direction ,

				float3 rightDir = normalize(cross(upDir,normalDir));// Get the right direction according to the up direction and the normal direction 
				upDir = normalize(cross(normalDir,rightDir));// According to the right direction and the normal direction, the upward defense line is obtained 
				float3 centerOffs = v.vertex.xyz-center;// Calculate the offset between the current vertex and the anchor 
				// Update model coordinates 
				float3 localPos = center+rightDir*centerOffs.x+upDir*centerOffs.y+normalDir*centerOffs.z;
				// Model space coordinates are converted to coordinates in clipping space 
				o.pos = mul(UNITY_MATRIX_MVP,float4(localPos,1));
				o.uv = TRANSFORM_TEX(v.texcoord,_MainTex);
				//TRANSFER_SHADOW_CASTER_NORMALOFFSET(o);
				return o;
			}
			fixed4 frag(v2f i):SV_TARGET
			{
    

				fixed4 c = tex2D(_MainTex,i.uv);
				c.rgb*=_Color.rgb;
				//SHADOW_CASTER_FRAGMENT(i);
				return c;
			}
			ENDCG
		}
		Pass {
    
			Tags {
     "LightMode" = "ShadowCaster" }
			
			CGPROGRAM
			
			#pragma vertex vert
			#pragma fragment frag
			
			#pragma multi_compile_shadowcaster
			
			#include "UnityCG.cginc"
			
			sampler2D _MainTex;
			float4 _MainTex_ST;
			fixed4 _Color;
			fixed _VerticalBillboarding;
			
			struct v2f {
     
			    float4 pos:SV_POSITION;
                float2 uv:TEXCOORD0;
			};
			
			v2f vert(appdata_base v) {
    
				v2f o;
				float4 offset;
				o.uv=TRANSFORM_TEX(v.texcoord,_MainTex);
				float3 center = float3(0,0,0);// Set the anchor of the billboard 
				float3 viewer =mul(_World2Object,float4(_WorldSpaceCameraPos,1));// Obtain the view coordinates in the model space 
				float3 normalDir = viewer-center;// According to the angle of view and the position of the anchor , Calculate the target normal direction 

				float3 upDir = abs(normalDir.y>0.999?float3(0,0,1):float3(0,1,0));// Calculate the upward direction , The premise is that it is not parallel to the normal direction ,

				float3 rightDir = normalize(cross(upDir,normalDir));// Get the right direction according to the up direction and the normal direction 
				upDir = normalize(cross(normalDir,rightDir));// According to the right direction and the normal direction, the upward defense line is obtained 
				float3 centerOffs = v.vertex.xyz-center;// Calculate the offset between the current vertex and the anchor 
				// Update model coordinates 
				float3 localPos = center+rightDir*centerOffs.x+upDir*centerOffs.y+normalDir*centerOffs.z;
				// Model space coordinates are converted to coordinates in clipping space 
				
				
				//TRANSFER_SHADOW_CASTER_NORMALOFFSET(o);
				o.pos = mul(UNITY_MATRIX_MVP,float4(localPos,1));

				TRANSFER_SHADOW_CASTER_NORMALOFFSET(o)
				return o;
			}
			
			fixed4 frag(v2f i) : SV_Target {
    
			    fixed4 tex=tex2D(_MainTex,i.uv);
                if(tex.a<0.5){
    
                    discard;
                }
                SHADOW_CASTER_FRAGMENT(i);
				
			}
			ENDCG
		}
		
	}
	Fallback "VertexLit"
}