Not a sphere

Virtual abstract scenery, Abstract digital art, Raytracing, Computer-rendered image, 2022. A golden square appears in many reflections forming a seemingly perfect sphere.
[Raytracing / Print and Video 2022]

Here I actually modelled “not a sphere”. Instead, the shape emerged automatically from experiments with a (single) golden square enclosed in a mirrored square shaft. The mirror images extend like a grid in two spatial directions. If the upper diameter of the shaft is larger than the lower, the mirror images appear to be on a perfect spherical surface.

The video below begins with a representation of a shaft diameter that is the same everywhere. The upper end continuously expands during the video and shrinks again from the middle of the video:

This is the setup used: