0x5f3759df — Fast inverse square root explained in detail

The appendix of this article has a slightly more intuitive explanation: http://blog.quenta.org/2012/09/0x5f3759df-appendix.html

Previously submitted: https://news.ycombinator.com/item?id=4526609

Also from another source: https://news.ycombinator.com/item?id=3115168