I'm pretty sure the strong curve is because (normal) floors are finite planes, and usually we don't look so close from the sphere's equator in real life. Once

I'm pretty sure the strong curve is because (normal) floors are finite planes, and usually we don't look so close from the sphere's equator in real life. Once I wrote a raytracer in Lisp based on pg's code in ANSI Common Lisp, so I've seen the results of changing camera positions.