CentralNotice From Wikipedia, the free encyclopedia Jump to: navigation , search Lighting and reflection calculations (shown here in the first-person shooter OpenArena ) use the fast inverse square root code to compute angles of incidence and reflection. Fast inverse square root (sometimes referred to as Fast InvSqrt() or by the hexadecimal constant 0x5f3759df ) is a method of calculating x −½ , the reciprocal (or multiplicative inverse) of a square root for a 32-bit floating point number in IEEE 754 floating point format . The algorithm was probably developed at Silicon Graphics in the early 1990s, and an implementation appeared in 1999 in the Quake III Arena source code, but the method did not appear on public forums such as Usenet until 2002 or 2003. [ 1 ] At the time, the primary advantage of the algorithm came from avoiding computationally expensive floating...