PLfft

by Tim C. Lueth, SG-Lib Toolbox: SolidGeometry 5.6 - PL/Point Lists
Introduced first in SolidGeometry 4.5, Creation date: 2019-04-20, Last change: 2025-09-14

same as CPLfft but for open contours

Description

Uses PLconnectopenends before using CPLfft

See Also: CPLfft , PLconnectopenends , VLBezierC

Example Illustration

Syntax

PLN=PLfft(PL,[])

Input Parameter

PL: Open Point List

Output Parameter

PLN: Frequency limited Contour

Examples


PLfft(PLsample(4),10)

Copyright 2019-2025 Tim C. Lueth. All rights reserved. The code is the property of Tim C. Lueth and may not be redistributed or modified without explicit written permission. This software may be used free of charge for academic research and teaching purposes only. Commercial use, redistribution, modification, or reverse engineering is strictly prohibited. Access to source code is restricted and granted only under specific agreements. For licensing inquiries or commercial use, please contact: Tim C. Lueth

Algorithm (Workflow)

This function, PLfft, is designed to process open point lists (PL) and generate a frequency-limited contour (PLN). It is part of the SolidGeometry library and was introduced by Tim Lueth in 2019.

Input Parameters

PL: An open point list representing a series of points in a 2D space.
varargin: Additional optional parameters that can be passed to the function.

Output

PLN: A frequency-limited contour derived from the input point list.

Algorithm Steps

The function begins by connecting the open ends of the point list PL using the function PLconnectopenends.
The connected point list is then processed by the CPLfft function, which applies a Fourier transform to limit the frequency of the contour.
The function calculates the vector norm between the transformed contour (CPL) and the first point of the original list (PL). It finds the index (e1) of the minimum distance.
The contour is circularly shifted so that the point with the minimum distance to the first point of PL is at the start.
The function recalculates the vector norm between the shifted contour and the last point of the original list, finding the index (e2) of the minimum distance.
The first point of the contour is set to the first point of the original list, and the point at index e2 is set to the last point of the original list.
The final frequency-limited contour (PLN) is extracted from the start to the index e2 of the shifted contour.
If no output is requested (nargout==0), the function plots the original point list and the frequency-limited contour using PLplot.

Algorithm explaination created using ChatGPT on 2025-08-18 23:28. (Please note: No guarantee for the correctness of this explanation)

Last html export of this page out of FM database by TL: 2025-09-21