# Some questions about FFT Wave Simulation

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Hello everyone,

I'm currently trying to implement a FFT Wave Simulation as proposed in Jerry Tessendorf's paper <Simulating Ocean Waves>. I read a lot papers, articles, tutorials, etc. but never understood the whole process. So I just started working on my own implementation, in the hope to achieve a better understanding while doing this. Well, it didn't work out that much

I hope you can help me with a few questions. For reasons of simplicity I will always refer to this blog post in my questions.

1. The equation for k is

What is the big L in this equation? The article just says "size of the height field" but what exactly does this mean?

2. The sigma sign in this equation is where i use my FFT, right?

3. h_tilde and exp(ikx) are both complex numbers. My height should obviously be a real number? Do I just use the real part of this equation in the end or is there anything else I don't understand?

This three questions should be enough. I promise I have more when these are answered

Thank you in advance!

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1.  L = length  . Name comes from 1d application of FFT.
2. that whole equation is FT  (without the fast) it is equivalent to FFT. Not only the SigmaSign
3. Use just real part, or impose some symmetry before FT to automatically get zero in imaginary part

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Thanks for the answer. It really cleared up a few things for me and I was able to continue on this project.

I have now finished the creation of the height field and surprisingly it really looks like ocean waves and the waves moves in the right direction :D

But I still got one problem which I couldn't solve after a few hours of debugging and I still don't know where to search for the origin of this problem.

The amplitudes of my waves are way to high. If I use the proposed values of L=2000 and V=600 my amplitudes go up to ~10000. If I change the A in the following equation to 0.0001 my amplitudes still go up to ~1000.

I really don't know why my waves are so huge but does anyone has an idea where to search for the error or what problem could cause the error?

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