Why do 3D models on the PS1 tend to shake and jitter like they do?

You know what I'm talking about. There was a game, I think Time Crisis, that had an island in its opening scene. We used to call it Earthquake Island because of how dramatically is pulsated on the screen. Why is this?

I've played PS1 games on an emulator, and even if you turn up the resolution so that the models look completely clear, they'll still shake around, changing shape with every movement. It's not as odd looking at the default resolution.

What's the technological reasons behind this? The N64 didn't have this problem.

Submitted December 29, 2014 at 03:01AM by jmf145 http://www.reddit.com/r/gadgets/comments/2qncvy/why_do_3d_models_on_the_ps1_tend_to_shake_and/