Getframe very slow in loop

I'm simulating a wave, and animating it by plotting each time step in a loop and using getframe() to store each frame in a struct. I'm using a movie instead of using pause to animate because I'd later like to save the movie.

When I comment out the getframe call, the entire script takes less than half a second to run, but with it, it takes more than 30 seconds.

u is the 2D array used to store the wave height, where each column is a position and each row is a timestep.

How do I make getframe take less time, or, failing that, is there another way I can animate the wave?

    % Initialises the figure, makes it invisible so the movie is the only
    % thing seen.
    figure('visible','off');
    hold on
    
    % Sets y limits, with padding
    ylim([min(u,[],'all') - 0.1 * range(u,'all'), max(u,[],'all') + 0.1*range(u,'all')]);
    
    % Initialises the object used to store the image frames
    F(length(t)) = struct('cdata',[],'colormap',[]);
    
    % Plots the initial position of the wave and stores the frame
    p = plot(x, u(1, :));
    F(1) = getframe(gcf);
    
    % Animates the wave
    for i = 2:length(t)
        
        % Updates the wave and stores the frame
        set(p, 'YData', u(i, :));
        F(i) = getframe(gcf);
        
    end

    % Makes figure visible again
    figure('visible', 'on');
    
    % Displays the movie
    movie(gcf, F, 1, fps);

Answer 1

[Gaurav Garg]

Hey Manav,

getFrame captures the whole frame of the current figure and saves it into a struct. So, it is expected to take this amount of time.

Alternatively, you can save the plot as an image and then create the movie from images.