unity的黑科技
https://docs.unity3d.com/Manual/SL-SubShaderTags.html
这里
reflectCamera.RenderWithShader(replacementShader, "Reflection");
SubShader {
Tags { "RenderType"="Opaque" "Reflection" = "RenderReflectionOpaque"}
LOD 300
Tags { "RenderType"="Opaque" "Reflection" = "RenderReflectionOpaque"}
LOD 300