quality loss when converting "warpings" with OCVWarp

Fiske Planetarium's "Climate Change in our Backyard" is available as 4k frames for free download as well as a VR experience. So, I tried out doing some conversions to see how much quality is being lost when I use OCVWarp to change the "format" between 4k fulldome, 4k 360 VR, 2k fulldome and "pre-warped". 

The results were interesting. 

1. 4k 360 VR to 2k fulldome was not as good as 4k 360 VR to 4k fulldome. I expected the reverse.

Zoomed in views of screenshots below:

This is the 4k frame bicubic resized to 2k.

4k 360 VR to 2k fulldome - shows aliasing for fine lines.

4k 360 VR to 4k fulldome - shows less aliasing, better than the above!

2. 4k 360 VR to "prewarped" was almost as good as 2k fulldome to "prewarped". From earlier experience, I know that if I directly try 4k fulldome to "prewarped", I would get aliasing artifacts, so better results are obtained from bicubic resize 4k to 2k and then "warp". That being the case, this result shows that I need not download 4k frames and redo the "warping" if I have good quality 4k 360 VR video.

This was warped from 2K frames.

This was warped from 4k 360 VR video.