Hello there, I need a timer so I can calculate the position of a particle every 20ms or so, what do you guys use for this?

Depends on the API you're using. For example, if you're in Cocoa, you'll likely want to use NSTimer.

This also may be of interest: http://www.sacredsoftware.net/tutorials/...tion.xhtml

Oh yes I forgot, I'm using Cocoa

EDIT: thanks, problem solved with NSTimer