Here is a short tutorial that I made which I included with a couple of radiant skydomes that I released. You can download the radiant skydomes here:
http://animaniac72.deviantart.com/art/Ray-MMD-Radiant-HDR-Skydome-2-Pack...

You can download the Ray-MMD Shader here:
https://github.com/ray-cast/ray-mmd

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