Help in creating video for particle trajectory

Question

AkB 2023-4-29

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1955254-help-in-creating-video-for-particle-trajectory

评论： Image Analyst 2023-5-2

I have position vectors as a function of time., say, x=[1 X 100] , z=[1 X 100] , where time vector is t=[1 X 100]

plot(x, z) gives the trajectory of particle. However, I need to make a video showing particle movement while creating the trajectory. Also, I need to denote the partclie as a 'rod' and its varying orientation along the path. The orientation as a function of time could be found as angle=[1 X 100] .

Please suggest.

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Answer 1

Image Analyst 2023-4-30

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https://ww2.mathworks.cn/matlabcentral/answers/1955254-help-in-creating-video-for-particle-trajectory#answer_1226039

See attached demo where I make a movie of a graph that changes over time. Adapt as needed.

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Ban 2023-4-30

In your code ('movie_made_from_surf.m'), if I replace surf(x,y,z) with plot(x1d(frameIndex), y1d(frameIndex)), it doesn't show any curve. Please help

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Answer 2

Image Analyst 2023-4-30

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1955254-help-in-creating-video-for-particle-trajectory#answer_1226144

在 MATLAB Online 中打开

movie_made_from_plot.m

Try this:

% Demo to create a movie file from a quadratic curve plot, and then optionally save it to disk as an avi video file.
%==============================================================================================
% Initialization code
clearvars;
clc;
workspace;
fontSize = 15;
numberOfFrames = 100;
saveVideo = true;
t = linspace(0, 6, numberOfFrames);
hFigure = figure('Name', 'Demo by Image Analyst', 'NumberTitle', 'off');
%==============================================================================================
% Get a list of x and z coordinates for every time.
xVelocity = 1;
x = xVelocity * t;
z = -(t - 3) .^ 2 + 9;
% See the final plot.
% plot(x, z, 'b-');
% grid on;
% return;
%==============================================================================================
% Set up the movie structure.
% Preallocate movie, which will be an array of structures.
% First get a cell array with all the frames.
if saveVideo
    allTheFrames = cell(numberOfFrames,1);
    vidHeight = 344;
    vidWidth = 446;
    allTheFrames(:) = {zeros(vidHeight, vidWidth, 3, 'uint8')};
    % Next get a cell array with all the colormaps.
    allTheColorMaps = cell(numberOfFrames,1);
    allTheColorMaps(:) = {zeros(256, 3)};
    % Now combine these to make the array of structures.
    myMovie = struct('cdata', allTheFrames, 'colormap', allTheColorMaps);
    % Create a VideoWriter object to write the video out to a new, different file.
    writerObj = VideoWriter('Delete Me.avi');
    open(writerObj);
    % Need to change from the default renderer to zbuffer to get it to work right.
    % openGL doesn't work and Painters is way too slow.
    set(gcf, 'renderer', 'zbuffer');
end
%==============================================================================================
% Create the movie.
% After this loop starts, BE SURE NOT TO RESIZE THE WINDOW AS IT'S SHOWING THE FRAMES, or else you won't be able to save it.
for frameIndex = 1 : numberOfFrames
    cla reset;
    % Enlarge figure to full screen.
    % 	set(gcf, 'Units', 'Normalized', 'Outerposition', [0, 0, 1, 1]);
    plot(x(1:frameIndex), z(1:frameIndex), 'b-', 'LineWidth', 3);
    xlabel('x', 'FontSize', fontSize);
    ylabel('z', 'FontSize', fontSize);
    axis('tight')
    xlim([0, 6]);
    ylim([0, 9]);
    grid on;
    caption = sprintf('Frame #%d of %d, t = %.1f', frameIndex, numberOfFrames, t(frameIndex));
    title(caption, 'FontSize', fontSize);
    drawnow;
    thisFrame = getframe(gcf);
    % Write this frame out to a new video file.
    if saveVideo
        %  	writeVideo(writerObj, thisFrame);
        myMovie(frameIndex) = thisFrame;
    end
end
if saveVideo
    % close(writerObj);
    %==============================================================================================
    % See if they want to replay the movie.
    message = sprintf('Done creating movie\nDo you want to play it?');
    button = questdlg(message, 'Continue?', 'Yes', 'No', 'Yes');
    drawnow;	% Refresh screen to get rid of dialog box remnants.
    close(hFigure);
    if strcmpi(button, 'Yes')
        hFigure = figure('Name', 'Demo by Image Analyst', 'NumberTitle', 'off');
        % Enlarge figure to full screen.
        % set(gcf, 'Units', 'Normalized', 'Outerposition', [0, 0, 1, 1]);
        title('Playing the movie we created', 'FontSize', fontSize);
        % Get rid of extra set of axes that it makes for some reason.
        axis off;
        % Play the movie.
        movie(myMovie);
        close(hFigure);
    end
    
    %==============================================================================================
    % See if they want to save the movie to an avi file on disk.
    promptMessage = sprintf('Do you want to save this movie to disk?');
    titleBarCaption = 'Continue?';
    button = questdlg(promptMessage, titleBarCaption, 'Yes', 'No', 'Yes');
    if strcmpi(button, 'yes')
        % Get the name of the file that the user wants to save.
        % Note, if you're saving an image you can use imsave() instead of uiputfile().
        startingFolder = pwd;
        defaultFileName = {'*.avi';'*.mp4';'*.mj2'}; %fullfile(startingFolder, '*.avi');
        [baseFileName, folder] = uiputfile(defaultFileName, 'Specify a file');
        if baseFileName == 0
            % User clicked the Cancel button.
            return;
        end
        fullFileName = fullfile(folder, baseFileName);
        % Create a video writer object with that file name.
        % The VideoWriter object must have a profile input argument, otherwise you get jpg.
        % Determine the format the user specified:
        [folder, baseFileName, ext] = fileparts(fullFileName);
        switch lower(ext)
            case '.jp2'
                profile = 'Archival';
            case '.mp4'
                profile = 'MPEG-4';
            otherwise
                % Either avi or some other invalid extension.
                profile = 'Uncompressed AVI';
        end
        % Commented out because it was already created above before the loop.
        % writerObj = VideoWriter(fullFileName, profile);
        % open(writerObj);
        % Write out all the frames.
        numberOfFrames = length(myMovie);
        for frameNumber = 1 : numberOfFrames
            writeVideo(writerObj, myMovie(frameNumber));
        end
        close(writerObj);
        message = sprintf('Finished creating movie file\n      %s.', fullFileName);
        uiwait(helpdlg(message));
    end
    % If using Windows, open the folder and video.
    if ispc && strcmpi(button, 'yes')
        if ~strcmpi(pwd, folder)
            % Open File Explorer to the folder where they saved the video, if it's not the current folder.
            winopen(folder);
        end
        winopen(fullFileName);
    end
end
uiwait(helpdlg('Done with demo!'));

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AkB 2023-5-1

编辑：Image Analyst 2023-5-2

在 MATLAB Online 中打开

swimmer_size.jpg

Thanks. It worked. But my particle's leng keeps changing over time of its movement. Please see the attached image of the swimmers at 2 different time points. However my code looks okay. Could you please suggest why does it happen ?

workspace;
fontSize = 15;
numberOfFrames = length(t);
saveVideo = true;
hFigure = figure('Name', 'Demo by Image Analyst', 'NumberTitle', 'off');
if saveVideo
    allTheFrames = cell(numberOfFrames,1);
    vidHeight = 344;
    vidWidth = 446;
    allTheFrames(:) = {zeros(vidHeight, vidWidth, 3, 'uint8')};
    allTheColorMaps = cell(numberOfFrames,1);
    allTheColorMaps(:) = {zeros(256, 3)};
    myMovie = struct('cdata', allTheFrames, 'colormap', allTheColorMaps);
    writerObj = VideoWriter('Swimmers in waves.avi');
    open(writerObj);
    set(gcf, 'renderer', 'zbuffer');
end
for frameIndex = 1 : numberOfFrames
    cla reset;
    
    xp1=x_vec(1,frameIndex);
    zp1=z_vec(1,frameIndex);
    phi_p1=phi_vec(1,frameIndex);
    
    xp6=x_vec(6,frameIndex);
    zp6=z_vec(6,frameIndex);
    phi_p6=phi_vec(6,frameIndex);
    
    xp9=x_vec(9,frameIndex);
    zp9=z_vec(9,frameIndex);
    phi_p9=phi_vec(9,frameIndex);
    
    lineSegmentLength = 0.1;
    xt1 = xp1 + (lineSegmentLength/2) * sind(phi_p1);
    xd1 = xp1 - (lineSegmentLength/2) * sind(phi_p1);
    zt1 = zp1 + (lineSegmentLength/2) * cosd(phi_p1);
    zd1 = zp1 - (lineSegmentLength/2) * cosd(phi_p1);
    
    xt6 = xp6 + (lineSegmentLength/2) * sind(phi_p6);
    xd6 = xp6 - (lineSegmentLength/2) * sind(phi_p6);
    zt6 = zp6 + (lineSegmentLength/2) * cosd(phi_p6);
    zd6 = zp6 - (lineSegmentLength/2) * cosd(phi_p6);
    
    xt9 = xp9 + (lineSegmentLength/2) * sind(phi_p9);
    xd9 = xp9 - (lineSegmentLength/2) * sind(phi_p9);
    zt9 = zp9 + (lineSegmentLength/2) * cosd(phi_p9);
    zd9 = zp9 - (lineSegmentLength/2) * cosd(phi_p9);
    
    xleft= -0.1 ;
    xright= 7 ;
    zup= -0.95 ;
    zdown= 0 ;
    XX=linspace(xleft,xright,0.2*length(t));
    ZZ=linspace(zup, zdown, 0.2*length(t));
    [X,Y] = meshgrid(XX,ZZ);
    
    T=t(1,frameIndex);
    ux=w1*A*exp(k*Y)*cos(k*X-w1*T);   
    uz=w1*A*exp(k*Y)*sin(k*X-w1*T);
    
    plot([xt1, xd1], [zt1, zd1], 'r', 'LineWidth', 3);
    hold on
    plot([xt6, xd6], [zt6, zd6], 'b', 'LineWidth', 3);
    hold on
    plot([xt9, xd9], [zt9, zd9], 'm', 'LineWidth', 3);
    xlabel('x (m)', 'FontSize', 25);
    ylabel('z (m)', 'FontSize', 25);
    xlim([xleft, xright]);
    ylim([zup, zdown+0.2]);
    caption = sprintf('t = %.1f', t(frameIndex));
    title([caption,' Seconds'], 'FontSize', 30);
    set(gca,'FontSize',20);
    drawnow;
    thisFrame = getframe(gcf);
    if saveVideo
        % 	   writeVideo(writerObj, thisFrame);
        myMovie(frameIndex) = thisFrame;
    end
end