Computing the Inverse Square Root
Turkowski Ken, Apple Computer, Inc. Cupertino, California. E-mail address: turk@apple.com
Introduction
In computer graphics calculations, the square root is often followed by a division, as when normalizing vectors:
This adds a significant amount of computational overhead, as a floating-point division typically costs much more than multiplication.
The cost of division may be mitigated by a reciprocation. This gem derives the method and provides an implementation for directly computing the inverse square root, f (x) = x−1/2.
Description of the Algorithm
The algorithm is noteworthy, as no divisions ...
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