system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How does depth perception work? Do you need two eyes to have depth perception?
gpt
Depth perception is our ability to judge distances.

This can be done approximately based on how much our eyes have to focus, how big something is, how much ground there is between us and it based on our height, etc... All of these are monocular cues, and are relatively unreliable compared to parallax. They are sufficient for many animals, but predators especially tend to prefer something more precise as it makes catching prey easier.

This is where binocular vision comes in. While many creatures have two eyes, having two eyes that both face forward is much rarer. This allows both eyes to look at something. The difference in the angle that both eyes must face gives us a much more reliable method of depth perception.