//world normal 
float3 wNor = normalize(i.wNor);
//view normal 
float3 vNor = mul(UNITY_MATRIX_V, float4(wNor, 0.0)).xyz;
//screen pos 
float2 scrPos = i.scrPos.xy / i.scrPos.w;
scrPos += vNor.xy * _Width * 0.001;//uv offset 
float depthTex = SAMPLE_DEPTH_TEXTURE(_CameraDepthTexture, scrPos);
float depth = LinearEyeDepth(depthTex);//view space depth 
float rim = saturate((depth - i.scrPos.w) / max(0.001, _Spread * 0.01));//稍作缩放, 可以不要
rim = smoothstep(min(_MinRange, 0.99), _MaxRange, rim);