Speed up frames per second

I'm trying to create a video/animation using a large amount of data. I have currently collated all 'marker' points and joined them using plot3, but I want to speed up the animation, as it's really slow. I have tried to create a video, but it kept appearing as empty for some reason?

Here is a sample of my code:

for i = 1:1033
    RPtoT = [RASIS(i,:); RT2(i,:); RT3(i,:)];
    idx = [1 2 3 1];
    plot3(RPtoT(idx,1), RPtoT(idx,2), RPtoT(idx,3), '-o', 'Color', 'g');
    
    axis equal
    hold on
    
    LPtoT = [LASIS(i,:); LT0(i,:); LT1(i,:)];
    idx = [1 2 3 1];
    plot3(LPtoT(idx,1), LPtoT(idx,2), LPtoT(idx,3), '-o', 'Color', 'g');
        
    
    RT = [RT0(i,:); RT1(i,:); RT2(i,:); RT3(i,:)]; 
    idx = [1 2 3 1 4 2 3 4];
    plot3(RT(idx,1),RT(idx,2),RT(idx,3),'-o', 'Color', 'g');
    LT = [LT0(i,:); LT1(i,:); LT2(i,:); LT3(i,:)];
    idx = [1 2 3 1 4 2 3 4];
    plot3(LT(idx,1),LT(idx,2),LT(idx,3),'-o', 'Color', 'g');
    hold off
    
    Mod = figure(1);
    fighandle = gcf();
    F = getframe(i);
end

I've tried using the movie function but I haven't noticed it doing anything since I added it to my code.

n = [1, 1000, 10:1000]
movie(F(i),n, 200)

Please bear in mind I'm not an experienced Matlab user, I'm still relatively new. Any help would be much appreciated! Thanks in advance!

[darova]

try gif animation

[Voss]

A few observations:

Your code seems to always plot in figure 1, but it is calling getframe on figure i, for i = 1:1033.

The variable F is overwritten each time the loop executes. I imagine you want to collect all the frames, not just the last one.

The second argument to movie is the number of times to play the movie (n), so I don't know why it would not be a scalar or what MATLAB does with non-scalar n.

A few questions: Is the call to movie just after the for loop? Does this code run as written? Does it produce an empty animation or does it produce a slow animation (maybe the slow animation you refer to is the plotting loop running as the plots are created)?

You might try replacing the last three lines inside the for loop with the following:

F(i) = getframe(); % getframe defaults to current axes

And try playing the movie like this:

movie(F,1,200); % I don't know whether 200 fps is too fast (seems pretty fast). 
                % Maybe 30 fps would be better to be able to see the plots change.

[MADRobot]

Hi Benjamin,

for some reason when I enter F(i) = getframe();, the script produces an error. However, a figure does pop up and start playing, do you know why this could be happening? Thanks!

[Voss]

I'm not sure. What does the error say?

[Adam Danz]

@MADRobot, always include the entire error message when reporting an error.

When there is no input to getframe() it uses the current axes: getframe(gca).

If there is no figure, it will create one.

I'm guessing that the error is either an indexing error with F(i) or the error is unrelated to this line.

Answer 1

[Adam Danz]

There are several steps you can take to speed up the animation.

Optimize the loop

See inline comments for recommendations. Some of these steps will be eliminated if you choose to implement the next section.

for i = 1:1033
    RPtoT = [RASIS(i,:); RT2(i,:); RT3(i,:)];
    idx = [1 2 3 1];  % this can be moved outside of the loop
    plot3(RPtoT(idx,1), RPtoT(idx,2), RPtoT(idx,3), '-o', 'Color', 'g');
    
    axis equal  % this can be moved outside of the loop
    hold on     % this can be moved outside of the loop
    
    LPtoT = [LASIS(i,:); LT0(i,:); LT1(i,:)];
    idx = [1 2 3 1];  % this can be removed since it's the same as the first "idx" variable.
    plot3(LPtoT(idx,1), LPtoT(idx,2), LPtoT(idx,3), '-o', 'Color', 'g');
        
    
    RT = [RT0(i,:); RT1(i,:); RT2(i,:); RT3(i,:)]; 
    idx = [1 2 3 1 4 2 3 4];  % this can be moved outside of the loop
    plot3(RT(idx,1),RT(idx,2),RT(idx,3),'-o', 'Color', 'g');
    LT = [LT0(i,:); LT1(i,:); LT2(i,:); LT3(i,:)];
    idx = [1 2 3 1 4 2 3 4];  % this can be removed since it's the same as the previous "idx" variable.
    plot3(LT(idx,1),LT(idx,2),LT(idx,3),'-o', 'Color', 'g');
    hold off % is this really needed?  If so, move it outside, after the loop.
    
    Mod = figure(1); % this should be moved outside of the loop. Are you even using the variable?
    fighandle = gcf(); % this is redundant; it's the same as "Mod", I think, and it can be moved outside of the loop; Are you even using this variable?
    F = getframe(i); % Why are you providing i as an input? 
end

Update line object data rather than adding additional line objects

Every time you call plot3() or any plotting function, you create a new line object. With 1033 iterations, that creates LOTS of objects and that will eventually slow down the execution. Instead, update the XData, YData, and XData properties of the line objects within the loop.

Here's an example you can apply to your loop. It only adjusts 1 plot3 object. It looks like you'll need to do this for 4 plot3 objects. You may also need to adjust the indexing to fit your data.

% DEMO

% Create axes and 1 plot3() object
ax = axes();
hold(ax,'on')
h1 = plot3(ax, nan,nan,nan, '-o', 'Color', 'g'); 

% Update the plot3 object
idx = [1 2 3 1];
for i = 1:10
    RPtoT = [1:5; 1:5; rand(1,5)]; 
    h1.XData = [h1.XData, RPtoT(idx,1).'];  % ignore warning or learn howo supress warnings
    h1.YData = [h1.YData, RPtoT(idx,2).'];  % ignore warning or learn howo supress warnings
    h1.ZData = [h1.ZData, RPtoT(idx,3).']; 
end

% Remove initial nan
h1.XData(1) = []; 
h1.YData(1) = []; 
h1.ZData(1) = []; 

Update the animation every few iterations instead of every iteration

If your animation is stil slow, update the animation every few iterations by using a conditional statement.

% outside of your loop
nIterations = 1033; 
updateIterations = 1 : 3 : nIterations;   % every 3 iterations
fig = gcf();  % better yet, fig = figure(); when you create the figure.
F(numel(updateIterations)) = struct('cdata',[],'colormap',[]);

% at the bottom of your loop
for i = 1:nIterations
    
     % [SKIPPING CODE.....]
     
     
     [captureFrame, frameNumber] = ismember(i,updateIterations); 
     if captureFrame
         F(frameNumber) = getframe(fig); 
     end
end

Alternatively you can capture all of the frames and try to use the fps input of the movie() function.