MATLAB Code Generating DXF Sinusoidal Curve

This MATLAB script demonstrates how to generate a DXF file containing a sinusoidal curve represented as a polyline with a controlled number of points. All units are in millimeters (mm).

function generateSinusoidalDXF(length1, numberOfPoints, wavelength, amplitude)
    % GUIDELINE:
    % This function generates a DXF file containing a sinusoidal curve represented
    % as a polyline with a controlled number of points. All units are in millimeters (mm).
    %
    % INPUTS:
    %   length1         - Length of the x-axis in millimeters (scalar, double).
    %   numberOfPoints  - Number of points to generate for the polyline (scalar, integer).
    %   wavelength      - Wavelength of the curve in millimeters (scalar, double).
    %   amplitude       - Amplitude of the curve in millimeters (scalar, double).
    %
    % OUTPUT:
    %   A DXF file with a descriptive name is saved in the current working directory.
    %
    % USAGE EXAMPLE:
    %   generateSinusoidalDXF(100, 200, 47.6, 2.76); 
    %
    % MODIFIED BY: YX
    % DATE: 27/Jan/2026

    % Close all figures and clear workspace variables (except inputs)
    close all;
    clc;

    % --- Validate inputs ---
    if nargin < 4
        error('Four input arguments required: length1, numberOfPoints, wavelength, and amplitude.');
    end

    if ~isnumeric(length1) || ~isscalar(length1) || length1 <= 0
        error('length1 must be a positive scalar value in millimeters.');
    end

    if ~isnumeric(numberOfPoints) || ~isscalar(numberOfPoints) || numberOfPoints <= 0
        error('numberOfPoints must be a positive integer value.');
    end
    
    if ~isnumeric(wavelength) || ~isscalar(wavelength) || wavelength <= 0
        error('wavelength must be a positive scalar value in millimeters.');
    end

    if ~isnumeric(amplitude) || ~isscalar(amplitude)
        error('amplitude must be a numeric scalar value in millimeters.');
    end

    numberOfPoints = round(numberOfPoints); % Ensure integer value

    % --- Derived parameters ---
    waveNumber = 2 * pi / wavelength;  % Wave number in radians/mm

    % --- Generate coordinates ---
    % Generate x-coordinates in millimeters
    x = linspace(0, length1, numberOfPoints);

    % Generate y-coordinates for the sinusoidal curve in millimeters
    % Note: Kept the logic (x + wavelength/4) from original code, which acts as a phase shift
    y = amplitude * sin(waveNumber * (x + wavelength / 4));

    % Combine x and y coordinates into a matrix
    coordinates = [x(:), y(:)];

    % --- Specify DXF file name ---
    % Filename now includes parameters to distinguish files
    dxfFileName = sprintf('sinusoidal_curve_%dpts_W%.1f_A%.2f.dxf', ...
                           numberOfPoints, wavelength, amplitude);

    % --- Write coordinates to DXF file ---
    writeDXF(dxfFileName, coordinates);

    % Notify user
    fprintf('DXF file saved as %s\n', dxfFileName);
end

function writeDXF(filename, coordinates)
    % Open file for writing
    fileID = fopen(filename, 'w');
    if fileID == -1
        error('Failed to open file for writing.');
    end

    % Write DXF Header with units set to millimeters
    fprintf(fileID, '0\nSECTION\n2\nHEADER\n');
    fprintf(fileID, '9\n$INSUNITS\n70\n4\n');  % 70 = integer value for units, 4 = mm
    fprintf(fileID, '0\nENDSEC\n');

    % Write TABLES, BLOCKS, and ENTITIES sections
    fprintf(fileID, '0\nSECTION\n2\nTABLES\n0\nENDSEC\n');
    fprintf(fileID, '0\nSECTION\n2\nBLOCKS\n0\nENDSEC\n');
    fprintf(fileID, '0\nSECTION\n2\nENTITIES\n');

    % Begin POLYLINE entity
    fprintf(fileID, '0\nPOLYLINE\n8\n0\n66\n1\n70\n0\n'); % 70=0 indicates a 2D polyline

    % Write each point (coordinates are in millimeters)
    for i = 1:size(coordinates, 1)
        fprintf(fileID, '0\nVERTEX\n8\n0\n10\n%f\n20\n%f\n', coordinates(i, 1), coordinates(i, 2));
    end

    % End POLYLINE entity
    fprintf(fileID, '0\nSEQEND\n');

    % End DXF
    fprintf(fileID, '0\nENDSEC\n0\nEOF\n');

    % Close file
    fclose(fileID);
end

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