Animation made of multiple 3D plots in Matlab App Designer

Question

I am trying to transcribe one of my scripts into App Designer in Matlab so that I easily distribute it to students. The idea is to show forces and moments acting in 6 degrees of freedom on a vehicle in real time (based on user input through a joystick). I am using a very simplistic animation made of multiple 3D arrow plots at the moment (which refreshes every 0.1 s), but it does the job. What I would like to get is shown in the first figure, whereas the second figure shows what I actually get in App Designer.

The relevant lines of code in App Designer which I use for the plotting are as follows:

function plot_ROV(app)
            % Plot the forces and moments acting on the ROV in the correct graph:
            quiver3(app.UIAxes,0,0,0,1,0,0);
            hold(app.UIAxes);
            quiver3(app.UIAxes,0,0,0,0,1,0);
            hold(app.UIAxes);
            quiver3(app.UIAxes,0,0,0,0,0,1);
            hold(app.UIAxes);
            quiver3(app.UIAxes,0,0,0,app.Surge,0,0,'LineWidth',5,'Color',app.Colors(1,:));
            hold(app.UIAxes);
            quiver3(app.UIAxes,0,0,0,0,app.Sway,0,'LineWidth',5,'Color',app.Colors(2,:));
            hold(app.UIAxes);
            quiver3(app.UIAxes,0,0,0,0,0,app.Heave,'LineWidth',5,'Color',app.Colors(3,:));
            hold(app.UIAxes);
            app.circular_arrow3([1,0,0],app.Roll,0.2,app.Colors(4,:));
            hold(app.UIAxes);
            app.circular_arrow3([0,1,0],app.Pitch,0.2,app.Colors(5,:));
            hold(app.UIAxes);
            app.circular_arrow3([0,0,1],app.Yaw,0.2,app.Colors(6,:));
            hold(app.UIAxes);
            legend(app.UIAxes,'x-axis','y-axis','z-axis','surge','sway','heave','roll','roll',...
                'pitch','pitch','yaw','yaw','Location','BestOutside');
        end

        function circular_arrow3(app,axis,angle,radius,color)
            % Generate the data for the circle in 2D space:
            np = 10;   % no. points
            a = linspace(0,angle*pi,np);
            p = [radius.*cos(a);radius.*sin(a);zeros(1,np)];

            % Select the correct rotation matrix depending on the axis:
            if sum((axis-[1,0,0]).^2)==0
                R = [0,0,1;0,1,0;-1,0,0];
            elseif sum((axis-[0,1,0]).^2)==0
                R = [1,0,0;0,0,-1;0,1,0];
                p(2,:) = - p(2,:);
            elseif sum((axis-[0,0,1]).^2)==0
                R = eye(3);
            else
                error('Only rotations about the x-, y- and z-axes are supported');
            end

            % Rotate the points:
            pr = zeros(size(p));
            for i=1:np
                pr(:,i) = R*p(:,i);
            end

            % Calculate the difference between the last two points:
            x = pr(1,end);
            y = pr(2,end);
            z = pr(3,end);
            u = pr(1,end)-pr(1,end-1);
            v = pr(2,end)-pr(2,end-1);
            w = pr(3,end)-pr(3,end-1);

            % Plot the points:
            plot3(app.UIAxes,pr(1,:),pr(2,:),pr(3,:),'LineWidth',4,'Color',color);
            hold(app.UIAxes);
            quiver3(app.UIAxes,x,y,z,u,v,w,'LineWidth',6,'Color',color);
        end

Now, by comparing the two figures, I think my problem is that the hold command is not working, at least not the way I intend it to: only the points from the last circular arrow are shown. Since I do not have much experience with App Designer, my feeling is I must have done a basic mistake.

Thanks in advance for the help!

I've never used App Designer, nevertheless, the problem related to `hold` could be that you always call it as `hold(app.UIAxes);` without specifying `on`. This could have the effect to toggle `on / off` the hold functionalty; also, one cal to `hold` should be enough. You can try either to remove all the calls but the first one or, better, to specify `on` in the call: `hold(app.UIAxes,'on`)`; — il_raffa, Jul 04 '18 at 08:14
Many thanks! It was that simple! I typically use `hold on` so never used `hold()` before. If you post the answer, I will vote and approve it. — Enrico Anderlini, Jul 04 '18 at 08:47

score 1 · Accepted Answer · answered Jul 04 '18 at 09:59

In the plot_ROV function you call hold several times providing only one input parameter (namely the handle of the axes) that is without specifying the on property (hold(app.UIAxes);.

If the hold function is called in such a way, its effect is to toggle the property on / off in each call.

You can fix the issue either:

removing all the calls to hold butg the first one: just on call is enough to "add" subsequents items in the axes through the plotting functions
you can keep all the calls, but you have to specify the on property

hold(app.UIAxes,'on');

For more information about the hold function you can refer to the hold on-line documentation

Animation made of multiple 3D plots in Matlab App Designer

1 Answers1