hdri / equirectangular render to cubemap image output

[Vianvolaeus]

For baked cubemaps in shaders.

[Vianvolaeus]

Found a potential way to use vector transforms to effectively 'split' / unfold the image cleanly into an identical mirror. (2:1 aspect)

We could then pass this output to something like this cubemap generator in which it'd then be Unity compatible, namely for things like fallback cubemaps in VRchat shaders.

Visually I think this would result in the default viewing angle being effectively the same as initally using a matcap, obviously with the directional movement of a cubemap once rotated away from that view.

It is probably a good idea to look into some kind of smoothing / blur solution for the final output, possibly with contrast / highlight boosting - should clear texture noise and give some better looking results.