The best advice I can give to golfers on reading greens is to find a spot 4-6' below the green surface and go there to look at the green. At eye-level, the green contours are more evident and you do not see any of the optical effect of the surrounds. Next, look around the edges of the green to where the water drains off. I know it's elemental, but you'd be surprised how many people never put 2+2 together.
The only time I ever got completely disoriented was when we were building Makalei Hawaii. It was on the side of a volcanic mountain at 1,200-1,800 feet. About a 12% gradient. You could see Maui on a clear day. However, the land down along the shore about 10 miles away was flatish for a couple mile (the result of successive lava flows ending into the ocean). What happened was the flat land began to appear as ocean and the shoreline as the horizon. Conversely, the ocean appeared to be the sky. My brain, reacting to the slope of the land and without any visual landmarks in the distance "tilted" what I was seeing to make the 12% I was standing on appear to be level. To add insult to injury, since everyone in Hawaii uses the "everything breaks to the ocean" logic, my father decided to have some greens break into the mountain. We had a very experienced Wadsworth shaper who remarked it was the 1st time in his 20 yrs of shaping he couldn't 'feel' level with his ass.