How do I know when volshow is done rendering?

I have a folder with hundreds of files containing 3D data. I want to loop through the files and output images to create a movie.

However, when I load new data to the volshow object, it takes a bit of time to render the scene. Hence, when I get the figure frame to write it to a file, I sometimes don't get the fully rendered scene. I don't want to add a pause after drawnow, because the rendering and data retireval is already quite slow. Is there a way to know exactly when volshow is done rendering so I can get the frame to write to an image?

obj = volshow(get_data(file(1)));
viewer = obj.Parent;
for i=1:length(file)
    obj.Data = get_data(file(i));
    drawnow
    frame = getframe(viewer.Parent);
    imwrite(frame.cdata, fullfile(save_dir, sprintf('%05i.jpg', i)))
end

[Walter Roberson]

Unfortunately, I do not know of any way to do this.

[Matt J]

Hence, when I get the figure frame to write it to a file, I sometimes don't get the fully rendered scene

If so, I think you should report it is a bug. drawnow is supposed to block further execution until figure updating is complete. That's the whole point of drawnow.