这个pixel local storage
frame fetch
可以一个pass做出soft particle/deferred lighting/soft edge water
programble blending
中间的东西在tile上
https://www.khronos.org/registry/OpenGL/extensions/EXT/EXT_shader_pixel_local_storage.txt
就不用mrt或者俩pass了 省两次带宽 store/load
https://www.arm.com/files/pdf/9_2015ATF_Korea_UnrealEngine.pdf