I have a basic understanding of sine wave generation. The problem I am facing is that as the input parameter for time gets larger, my sine wave falls apart and starts to look really ugly.

I'd like to calculate a sine wave without depending on an ever increasing time value. How can I do this?


1 Answer 1


You could restart your time value every 2pi:

if(time > 2*pi)
  time -= 2*pi;

If is still okay to increase your time variable infinitely but the input for the sine is to large, just use fmod(time, 2*pi).

  • \$\begingroup\$ thank you, using fmod worked. It seemed to keep the values between 2*pi. Quick question, what does fmod do? I read this: tutorialspoint.com/c_standard_library/c_function_fmod.htm it says fmod returns the remainder but I don't get why it works. \$\endgroup\$
    – tmp
    Sep 5, 2015 at 17:27
  • 1
    \$\begingroup\$ basically it returns r in the equation x = n*y + r where x and y are the inputs and n is an integer. \$\endgroup\$ Sep 5, 2015 at 18:25
  • \$\begingroup\$ The reason you hit the issue you did is that as floating point numbers get larger, they lose accuracy. For instance if you start at zero and add one to a floating point number in an infinite loop, there will come a point where adding the 1 results in the same value (ie will have no effect) \$\endgroup\$
    – Alan Wolfe
    Sep 6, 2015 at 0:52
  • \$\begingroup\$ @ratchetfreak so is fmod like the modulus operation? \$\endgroup\$
    – tmp
    Sep 6, 2015 at 15:23

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