Fourier transform (FT) of arbitrary point sets.
how to use this applet:
Click new motif to start drawing a new point set. Then select one of the colors, which correspond to different scattering strengths (1-9) and click on the left canvas to position your points. Then click Fourier transform to calculate the discrete Fourier transform of that point set. You may choose to calculate the FT for a 100x100, 200x200 or 300x300 pixel image. X and Y in Fourier space range from -0.5 to +0.5 and the point coordinates from -50 to +50.