OK, so I’ve been playing with a new Core Image screen-saver as my background, and this one was just too awesome not to share.

Basically, your desktop picture is underwater and there are randomly-generated gentle ripples across the surface that reflect off the sides of the screen properly.

Click screen-shot for video (768*480 h.264 mp4, scaled from 1440*900, approx 15MB)

Or, a YouTube link for the h.264-impaired.

As you can maybe see when I invoke top, the ScreenSaverEngine is using ~11% of one core, with the bulk of the CPU being eaten at that point by the screen capture tool. It’s not tons, but you’re certainly going to want to kill it if you have an encoding job to do, or you want to play a game.

The one downside is that you basically have to feed an image to the screen-saver to overlay the water onto (I use the same image as my desktop background). That is to say, you can’t have it running transparently above your actual desktop, for example so that it could be overlaid on cycling random backgrounds.