Fast Digital Sine Oscillator

I originally intended this blog to be about math and digital signal processing as well and not just about C++. Since I recently answered a programming forum question regarding efficient generation of sine waves and took the time to code one in — surprize — C++, I thought to myself, why not sharing the code along with explanations about how it works.

If you’re interested in software synthesizers in general or generating digital representations of DTMF tones and don’t want to waste many CPU cycles when generating sine waves, keep on reading.

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Fast Inverse Square Root

The article “fast inverse sqrt” came to my attention. It shows a small function written in C which is amazingly fast and approximates sqrt(1/x) pretty well. Appearently it was used in the Quake source code to speed up vector normalizations. But how does it work? Also, can it be improved?