Looking like he’s holding Spode chimney up. My hubby allowed me to get him to hold his hand up as if he was leaning on the chimney and holding it up. It works surprisingly well. I’d seen this optical trick a few times and thought I would try to replicate it.
I think this counts as a visual illusion. I took a photo of a mince pie tin and moved it round in an app. When I looked at it, it looked like some of them looked like craters and some like they protrude. I think this is because the shading is throwing the light in opposite directions. The middle row is the most confusing.