1. Join any world with an AO option, e.g. https://vrchat.com/home/world/wrld_c7f6eeab-b2e7-4926-866a-a4ae3983b674
  2. Make sure to turn the AO slider all the way on.
  3. Open camera and observe how the AO layer is horizontally stretched.
If you take a picture, shrink it by 2x horizontally and apply on top of itself using 'darken' blend mode, you can kind of see how the ambient occlusion actually matches the left half of the picture.