User input during animation

9 views (last 30 days)
Ted Theodosopoulos
Ted Theodosopoulos on 29 Jun 2021
Commented: Walter Roberson on 3 Jul 2021
I have created an animation that graphs the motion of a test particle under the influence of a force field in 2D and I want to add a user interface. I'd like the user to be able to nudge the test particle by using the keyboard, e.g. the arrow keys. I'd like the user input to be interpreted as a variable in the program, so it can be added to the internal variables that are being graphed. I'd like this to happen without interrupting the animation. How might this be possible to accomplish in Matlab?
Ted Theodosopoulos
Ted Theodosopoulos on 1 Jul 2021
My animation is based on a simple for-loop with short pauses between the plotting of individual points of a trajectory. I'd like the user to be able to influence this trajectory, as they are watching it play out. Does this make sense?

Sign in to comment.

Answers (1)

Walter Roberson
Walter Roberson on 1 Jul 2021
Use a WIndowsKeyPressFcn callback, and check the event information to figure out which key was pressed in order to figure out what changes to make to your variables. Use one of the methods of sharing variables to get the data to the compute loop.
Your compute loop will need to periodically pause() or drawnow() to receive the interrupts, but it has to use one of those to make the animation visible anyhow.
Walter Roberson
Walter Roberson on 3 Jul 2021
function fig1_key_callback(hObject, event, handles)
xv = handles.particle_xv;
yv = handles.particle_yv;
switch event.Key
case 'leftarrow'
xv = xv - 5;
case 'rightarrow'
xv = xv + 5;
case 'uparrow'
yv = yv + 5;
case 'downarrow'
yv = yv - 5;
case 'q'
handles.quit = true;
%do nothing
handles.particle_xv = xv;
handles.particle_yv = yv;
guidata(hObject, handles)
function processing_loop(hObject, event, handles)
handles.x = x0; handles.y = y0; handles.quit = false;
handles.xv = randi([-10 10]); handles.yv = randi([-10 10]);
guidata(hObject, handles);
h = animatedline(handles.x, handles.y);
while true
handles = guidata(hObject); %pull back updates to handles
if handles.quit
handles.quit = false;
handles.x = handles.x + handles.xv;
handles.y = handles.y + handles.yv;
addpoints(h, handles.x, handles.y);
guidata(hObject, handles);
In this demonstration, the user does not control the x or y position directly, and instead affects the velocity, nudging it higher or lower (including negative).

Sign in to comment.


Find more on Animation in Help Center and File Exchange




Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!