About highlights Facula always look at camera，post have shader code，help!

Shader"Custom/Facula"
{
Properties
{
_MainTex ("Texture", 2D) = "white" {}
_MainPower ("TexturePower", Range(1.0,3.0)) = 1.6
_MainAlpha ("MainAlpha", Range(0.0,1.0)) = 1
_TextureFac ("TextureFacula (Alpha)", 2D) = "white" {}
_RimColor ("RimColor", Color) = (1,0,0,0)
_RimPower ("RimPower", Range(0.1,5.0)) = 0.1
_FaculaColor ("FaculaColor", Color) = (1,1,1,0)
_FaculaPower ("FaculaPower", Range(0.0,2.0)) = 0.4
}
SubShader
{
Tags {"Queue" = "Transparent"}
ZWrite Off
ZTest Always
CGPROGRAM
#include "UnityCG.cginc"
#pragma surface surf Lambert alpha:fade interpolateview noshadow nofog noforwardadd exclude_path:deferred
structInput
{
float2 uv_MainTex;
float2 uv_TextureFac;
float3 viewDir;
float4 screenPos;
};
sampler2D _MainTex;
float _MainPower;
float _MainAlpha;
sampler2D _TextureFac;
float4 _RimColor;
float _RimPower;
float4 _FaculaColor;
float _FaculaPower;
voidsurf (Input IN, inoutSurfaceOutput o)
{
o.Albedo = tex2D (_MainTex, IN.uv_MainTex).rgb*_MainPower;
fixed dotValue=dot (normalize(IN.viewDir), o.Normal);
if(dotValue<=0.3)
{
half rim = 1.0 - saturate(dotValue);
o.Emission = _RimColor.rgb * pow (rim, _RimPower);
}
float2 screenUV = IN.screenPos.xy / IN.screenPos.w;
screenUV=screenUV/_ScreenParams.xy;
//fixed alpha=tex2D(_TextureFac,screenUV).a; //no facula?
fixed alpha=tex2D(_TextureFac,IN.uv_TextureFac).a;
o.Emission += _FaculaColor*alpha*_FaculaPower;
o.Alpha=_MainAlpha;
}
ENDCG
}
Fallback"Diffuse"
}