Help in creating video for particle trajectory

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.

Answer 1

[Image Analyst]

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

[Ban]

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

Answer 2

[Image Analyst]

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!'));

[Ban]

This works. But I need two more things.

I need to denote the particle as a 'rod' or 'ellipsoidal' marker. And this 'rod' or 'ellipsoidal' marker also changes its orientation along the path. I have the orientation as a function of time and could be found as angle=[1 X 100] .

Please suggest how do I incorporate these.

[Image Analyst]

@Ban are you the same person as @AkB? Anyway, you can use line() or plot() to put a second line segment wherever you want.

[Ban]

yes, somehow both the accounts gets mixedup.

I still do not get how to denote the particle as a 'rod' or 'ellipsoidal' marker with orientation.

[Image Analyst]

Just figure out the [x1, x2] and [y1, y2] for the two endpoints. It's just simple algebra and trigonometry. I'm sure you can handle it. In fact, you probably already have it done by now. Like if the current point is (x,y), then

lineSegmentLength = 2;
angle = 45; % Degrees or whatever.
x1 = x - (lineSegmentLength/2) * cosd(angle);
x2 = x + (lineSegmentLength/2) * cosd(angle);
y1 = y - (lineSegmentLength/2) * sind(angle);
xy = y + (lineSegmentLength/2) * sind(angle);
plot([x1, x2], [y1, y2], 'r-', 'LineWidth', 4);

[AkB]

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

[Image Analyst]

@AkB The above code doesn't run. Please attach the m-file with the paperclip icon.