On Saturday, 29. May 2010 12:40:17 Michael Menegakis wrote: > Is it in the end result of the gameplay completely safe? Does it have > a probability to create inconsistencies or at least visual > discrepancies?
This "hack" is actually an approximation of the inverse square root function,
by means of the Newton-Raphson-iteration which is broken off after the first
iteration. The trick lies in choosing a good initial value for that iteration.
I haven't understood it myself either why it works, but choosing of initial
value seems to be done with this line:
t.i = 0x5f3759df - ( t.i >> 1 ); // what the fuck?
This code apparently works for all float numbers (except for the negative ones
of course that cannot be computed) to good accuracy. There's a paper written
about this here:
http://www.lomont.org/Math/Papers/2003/InvSqrt.pdf
--
Thilo Schulz
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