Fig. 2

Fourier descriptor limitations. Here, the right nasal cavity section (left side in the image; view from the front) is bounded by a closed curve, which can be represented parametrically as the periodic function p, with two points on p (t=0.5 and t=0 which is equal to t=1) shown for illustrative purposes. The Fourier decomposition of p is thus well-defined (however, an infinite set of parametric functions can be used to represent the boundary, and the choice of p is thus to some extent arbitrary). The left section, however, has congestion, thus requiring two closed curves to represent. This complicates the Fourier analysis