挖空并且始终面对相机

Shader "JZ/CusustomMaskLightShader"
{
    Properties
    {   
        [Enable]_ScaleX("缩放X",float) = 1
        [Enable]_ScaleY("缩放Y",float) = 1
        _OffsetCenterX("亮点X",Range(0,1))=0.5
        _OffsetCenterY("亮点Y",Range(0,1))=0.5
        _BaseColor("背景色",Color) = (0,0,0,1)
        _SmoothStep("柔和度",Range(0,0.5))=0
        _BaseMul("范围(相乘)",float)=100
        _BasePow("范围(对比度pow)",float)=100
        _BaseAdd("整体范围(相加)",Range(0,1))=0
        _CirWidth("圆形的高",float)=1.5
        _CirHeight("圆形的宽",float)=1.5
        _FinalAlpha("整体透明值",Range(0,1))=1
       
    }
 
    SubShader
    {
        Tags { "Queue"="Transparent+1999" "RenderType" = "Transparent" "IgnoreProjector" = "True" "RenderPipeline" = "UniversalPipeline" }
        LOD 100
 
        Pass
        {
            Name "CustomShader"
            Blend SrcAlpha OneMinusSrcAlpha 
            ZTest Always
            HLSLPROGRAM
            // Required to compile gles 2.0 with standard srp library
            
            #pragma vertex vert
            #pragma fragment frag
        
            #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Core.hlsl"

 
 
            struct Attributes
            {
                float4 positionOS       : POSITION;
                float2 uv               : TEXCOORD0;
            };
 
            struct Varyings
            {
                float4 positionCS       : SV_POSITION;
                float2 uv               : TEXCOORD0;
               
            };
 
            CBUFFER_START(UnityPerMaterial)
            half4 _BaseColor;
            float2 _LightPos;
            float _SmoothStep;
            float _BasePow;
            float _BaseMul;
            float _BaseAdd;
          
            float _CirWidth;
            float _CirHeight;
            float _FinalAlpha;
          
            float _OffsetCenterX;
            float _OffsetCenterY;
            float _ScaleX;
            float _ScaleY;
            CBUFFER_END
         
            float4x4 Scale(float4 scale)
			{
				return float4x4(scale.x, 0.0, 0.0, 0.0,
					0.0, scale.y, 0.0, 0.0,
					0.0, 0.0, scale.z, 0.0,
					0.0, 0.0, 0.0, 1.0);
			}

 
            Varyings vert(Attributes v)
            {
                Varyings o = (Varyings)0;
                v.positionOS = mul(Scale(float4(_ScaleX,1,_ScaleY,1)), v.positionOS);
                float4 ori_pos=mul(UNITY_MATRIX_MV,float4(0,0,0,1));
                float4 positionOS= v.positionOS;
                positionOS.y=positionOS.z;
                positionOS.z=0;
                positionOS.xyz+=ori_pos.xyz;
                o.positionCS=mul(UNITY_MATRIX_P,positionOS*1);
              //  o.positionCS = TransformObjectToHClip(v.positionOS.xyz);

              


                o.uv=v.uv;
                return o;
            }
 
            half4 frag(Varyings i) : SV_Target
            {
             
                
                float2 screen_pos=i.uv;
                float2 light_pos =float2(_OffsetCenterX,_OffsetCenterY);
                float  Width=_ScaleX/_ScaleY;
                float  Height=_ScaleY/_ScaleX;
                float light_distance=0;
                if  (_ScaleX>_ScaleY)
                {
                   
                    screen_pos.x/=_CirHeight;
                    screen_pos.y/=_CirWidth;
                    screen_pos.x*=Width;
                    light_pos=float2((light_pos.x*Width)/_CirHeight ,(light_pos.y)/_CirWidth);
                    light_distance=length(screen_pos-light_pos);
                    light_distance=smoothstep(_SmoothStep,1-_SmoothStep,light_distance);
                    light_distance=saturate(pow(max((light_distance*_BaseMul),0),_BasePow)+_BaseAdd);
                }
                else
                {
                   
                    screen_pos.x/=_CirHeight;
                    screen_pos.y/=_CirWidth;
                    screen_pos.y*=Height;
                    light_pos=float2((light_pos.x)/_CirHeight ,(light_pos.y*Height)/_CirWidth);
                    light_distance=length(screen_pos-light_pos);
                    light_distance=smoothstep(_SmoothStep,1-_SmoothStep,light_distance);
                    light_distance=saturate(pow(max((light_distance*_BaseMul),0),max(_BasePow,0))+_BaseAdd);
                }
              
                half4 c =_BaseColor;
                light_distance=lerp(light_distance,_FinalAlpha,light_distance);
                return float4(c.xyz,light_distance);
            }
            ENDHLSL
        }
    }
}