Unity shader uses rendered texture to achieve glass effect

Implementation method ：

• adopt cubemap Achieve reflection effect
• adopt GrabPass Get the rendered texture , Match the offset of the upper normal texture , Realize the refraction effect of glass .

Realization effect ：

Prepare in advance ：

Find the location of the cube cubemap

Code ：

// Upgrade NOTE: replaced '_Object2World' with 'unity_ObjectToWorld'
// Upgrade NOTE: replaced 'mul(UNITY_MATRIX_MVP,*)' with 'UnityObjectToClipPos(*)'

Shader "Custom/Chapter10-GlassRefraction"
{
    
    Properties
    {
    
    // The texture of glass 
    _MainTex("Main Tex",2D)="while"{
    }
    // Normal texture of glass 
    _BumpMap("Normal Map",2D)="bump"{
    }
    // Environment texture used to simulate cube reflection 
    _CubeMap("Environment Cubemap",Cube)="_Skybox"{
    }
    // Control the distortion of the image when the glass refracts , Yes GtabPass The degree of distortion treatment 
    _Distortion("Distortion",Range(0,100))=10
    // Used to control the proportion of refraction 
    _RefractAmount("Refract Amount",Range(0.0,1.0))=1.0
    }
    SubShader
    {
    
        Tags {
     "Queue"="Transparent" "RenderType"="Opaque" }

        // use GrabPass To get the current screen texture stored in _RefractionTex in , As the refraction texture of the cube 
        GrabPass{
    "_RefractionTex"}

        Pass{
    

        CGPROGRAM
        #pragma vertex vert
        #pragma fragment frag
        #include "UnityCG.cginc"
        sampler2D _MainTex;
        float4 _MainTex_ST;
        sampler2D _BumpMap;
        float4 _BumpMap_ST;
        samplerCUBE _CubeMap;
        float _Distortion;
        fixed _RefractAmount;
        sampler2D _RefractionTex;
        // The size of the texture element that refracts , Later, we need to use 
        float4 _RefractionTex_TexelSize;

        // Vertex shader input structure 
        struct a2v {
    
			float4 vertex : POSITION;
			float3 normal : NORMAL;
            // Tangent line 
			float4 tangent : TANGENT; 
            // Texture coordinates 
			float2 texcoord: TEXCOORD0;
		};
			
        // Input structure of fragment shader 
		struct v2f {
    
			float4 pos : SV_POSITION;
            // The coordinates of the refracted texture 
			float4 scrPos : TEXCOORD0;
            // Texture coordinates , Normal and reflective 
			float4 uv : TEXCOORD1;
            // Transformation matrix 
			float4 TtoW0 : TEXCOORD2;  
			float4 TtoW1 : TEXCOORD3;  
			float4 TtoW2 : TEXCOORD4; 
		};

       v2f vert(a2v v){
    
       v2f o;
       o.pos=UnityObjectToClipPos(v.vertex);
       // Get the sampling coordinates of the screen texture 
       o.scrPos=ComputeGrabScreenPos(o.pos);
       // The obtained texture coordinates are stored in uv The four one. float Value 
       o.uv.xy=TRANSFORM_TEX(v.texcoord,_MainTex);
       o.uv.zw=TRANSFORM_TEX(v.texcoord,_BumpMap);
       float3 worldPos =mul(unity_ObjectToWorld,v.vertex);
       // Normal in world space , Tangent and sub tangent , Used to find the transformation matrix from tangent space to world space 
       fixed3 worldNormal = UnityObjectToWorldNormal(v.normal);
       fixed3 worldTangent =UnityObjectToWorldDir(v.tangent.xyz);
       // The sub tangent obtains the direction by cross multiplying the normal and tangent 
       fixed3 worldBinormal =cross(worldNormal,worldTangent)*v.tangent.w;

       // Transform matrix storage , And store the world coordinates in w variable , Save space 
       o.TtoW0=float4(worldTangent.x,worldBinormal.x,worldNormal.x,worldPos.x);
       o.TtoW1=float4(worldTangent.y,worldBinormal.y,worldNormal.x,worldPos.y);
       o.TtoW2=float4(worldTangent.z,worldBinormal.z,worldNormal.x,worldPos.z);

       return o;
       }

       fixed4 frag(v2f i):SV_Target{
    
       // World coordinates 
       float3 worldPos =float3(i.TtoW0.w,i.TtoW1.w,i.TtoW2.w);
       // Look in the direction 
       fixed3 worldViewDir =normalize(UnityWorldSpaceViewDir(worldPos));
       // Normal in tangent space 
       fixed3 bump =UnpackNormal(tex2D(_BumpMap,i.uv.zw));

       // Offset of refraction texture coordinates 
       float2 offset=bump.xy*_Distortion*_RefractionTex_TexelSize;
       i.scrPos.xy+=offset;
       fixed3 RefrCol=tex2D(_RefractionTex,i.scrPos.xy/i.scrPos.w).rgb;

       // normal transformation , matrix multiplication , Transform normals into world space 
       bump =normalize(half3(dot(i.TtoW0.xyz,bump),dot(i.TtoW1.xyz,bump),dot(i.TtoW2.xyz,bump)));
       // Reflect light 
       fixed3 reflDir =reflect(-worldViewDir,bump);
       // Color of glass 
       fixed4 texColor =tex2D(_MainTex,i.uv.xy);
       // The color obtained by sampling the stereo texture is multiplied by the glass color to obtain the reflected color 
       fixed3 reflCol =texCUBE(_CubeMap,reflDir).rgb*texColor.rgb;
       // The final color is reflection and refraction multiplied by their respective weights and added together 
       fixed3 finalColor =reflDir*(1-_RefractAmount)+RefrCol*_RefractAmount;

       return fixed4(finalColor,1.0);
       }
        ENDCG
        }
    }
    FallBack "Diffuse"
}