Two odd visual effects

If you look at uneven snow (heaps thrown aside when clearing pathways is good, but a partially-melted smooth snow surface works too) through a vertical-horizontal grid, such as the fine wire one-centimetre mesh embedded in reinforced glass windows and doors, you may see the lumps and bumps as tilted blocks or pyramids.

If you look with one eye covered at a photograph with vivid colours and strong depth cues you may see it in 3D. The effect is quite unmistakable and was a complete surprise to me when I first noticed it. I was drinking coffee while reading New Scientist, and the raised mug got between the sightline of one eye and a picture on the page, and the picture suddenly sprang into a 3D image. I almost spilled the coffee.

These two effects may be well-known but I've never heard of them.