Plot 3D Animation

Good morning,

I am currently developing my master thesis in MATLAB, developing an academic Multibody Systems algorithm. I am currently having some difficulties doing my debug and I was trying to code a 3D Animated Plot to try and understand what was my system behaviour.

This is my current code:

%% 3D Animation Plot
if strcmp(anigraph,'yes') == 1 || strcmp(anigraph,'YES') == 1 || strcmp(anigraph,'Yes') == 1
    
    NPoint = Joints.NPoint; %Number of Points
    origin = [0,0,0]; %Origin

    %% Plot the Graphic
    for f = 1:1667:c %Size of the Point StructStruct
        
       %Plot First two Points of each iteration
       strucPos = Points{1,f};
       vecpos = strucPos(2).Position;
       vecpos = vecpos';
       %Initiate the 3D Plot
       m = plot3([origin(1) vecpos(1)],[origin(2) vecpos(2)],[origin(3) vecpos(3)],'LineWidth',2);
       hold on
       axis auto
       grid on
       %Retrieve the Position Information and plot
       for h = 2:NPoint 
            % Previous Point Pos Vector
            prevecpos = strucPos(h-1).Position;
            prevecpos = Impose_Column(prevecpos);
            prevecpos = prevecpos';
            % Foward Point Pos Vector
            vecpos = strucPos(h).Position;
            vecpos = Impose_Column(vecpos);
            vecpos = vecpos';     
            %Plot These Points
            plot3([prevecpos(1) vecpos(1)],[prevecpos(2) vecpos(2)],[prevecpos(3) vecpos(3)],'LineWidth',2),
            hold on
            pause(TimeStep);
       end
    end
    hold off
end

I followed this code and video: Youtube

All my data for the plot is stored in a cell with multiple structs. Here is the example of one of these Structs, I desire to use only the data from the first column.

I have been trying to plot something like this for every iteration:

However, I am only being able to plot the first vector, can someone help me understand what I am missing on my code? My main difficulty is that the number of points change with the system that I try to simulate.

Thank you for all your help and attention.

Tiago

EDIT: Added a new code that is now able to plot the first iteration atleast.

Answer 1

[Karim]

not sure witouth some example data, could you share for instance the struct holding the time history of the solution?

As a tip, I would only update the plot once at each time step. You can use plot3 to plot multiple vectors at once, just seperate them with nan's. I will add a small example below.

MyGrid = [ -0.5 0 0; 0.5 0 0; 0 0 0; 0 -2 0; -1.5 -1.5 0; 1.5 -1.5 0];
MyPoints = [1 2; 3 4; 1 5; 2 6]; % column 1 gives the start point of each vector, column 2 the stop point

figure
plot3( reshape([MyGrid(MyPoints(:,1),1)';MyGrid(MyPoints(:,2),1)';NaN(1,numel(MyPoints(:,1)))],1,[]),...
       reshape([MyGrid(MyPoints(:,1),2)';MyGrid(MyPoints(:,2),2)';NaN(1,numel(MyPoints(:,1)))],1,[]),...
       reshape([MyGrid(MyPoints(:,1),3)';MyGrid(MyPoints(:,2),3)';NaN(1,numel(MyPoints(:,1)))],1,[]),'r')
grid on
view([0 90])

% now plot the figure again and rotate it
figure
m = plot3( reshape([MyGrid(MyPoints(:,1),1)';MyGrid(MyPoints(:,2),1)';NaN(1,numel(MyPoints(:,1)))],1,[]),...
       reshape([MyGrid(MyPoints(:,1),2)';MyGrid(MyPoints(:,2),2)';NaN(1,numel(MyPoints(:,1)))],1,[]),...
       reshape([MyGrid(MyPoints(:,1),3)';MyGrid(MyPoints(:,2),3)';NaN(1,numel(MyPoints(:,1)))],1,[]),'r');
grid on
view([0 90])

% to update the figure, we can use "m" directly, say we want to rotate the
% grid by 30 degrees:

RotGrid = (rotz(30) * MyGrid')';

% note you can put this in a simple loop

m.XData = reshape([RotGrid(MyPoints(:,1),1)';RotGrid(MyPoints(:,2),1)';NaN(1,numel(MyPoints(:,1)))],1,[]);
m.YData = reshape([RotGrid(MyPoints(:,1),2)';RotGrid(MyPoints(:,2),2)';NaN(1,numel(MyPoints(:,1)))],1,[]);
m.ZData = reshape([RotGrid(MyPoints(:,1),3)';RotGrid(MyPoints(:,2),3)';NaN(1,numel(MyPoints(:,1)))],1,[]);

[Tiago Carvalho]

Hello, I never used the reshape function so I have to read more about it before I have any questions, but here it is the example struct for this specific case. Thank you for your time!

EDIT: I have read the answer I do not think that will solve my problem, since my issue is that I don't know how many points I will have for each animation since it depends on the system that I am simulating. If I knew them from the beginning then I think that your would be better suited than the one I tried.

2nd Edit: Also right now I was able to plot every iteration into the graphic but I wanted to be able to animate them instead of having all of them plotted.

[Karim]

based on the example data, i modified the code to a working example, see below.

note you will nee to run it locally, online it won't display the animation but only a single plot

load('examplestruct.mat')
anigraph = "yes";
Joints.NPoint = 6;

TimeStep = 2.5e-3;

%% 3D Animation Plot
if strcmp(anigraph,'yes')
    
    NPoint = Joints.NPoint; %Number of Points
    
    %% Initiate the 3D Plot
    % first get the grid for the inital iteration
    MyGrid = horzcat( Points{1,1}.Position );
    % build the connectivity
    MyPoints = [1:(Joints.NPoint-1); 2:Joints.NPoint];
    
    figure
    m = plot3( reshape([MyGrid(1,MyPoints(1,:));MyGrid(1,MyPoints(2,:));NaN(1,NPoint-1)],1,[]),...
               reshape([MyGrid(2,MyPoints(1,:));MyGrid(2,MyPoints(2,:));NaN(1,NPoint-1)],1,[]),...
               reshape([MyGrid(3,MyPoints(1,:));MyGrid(3,MyPoints(2,:));NaN(1,NPoint-1)],1,[]),'r');
    
    axis auto
    grid on
    
    % set limits...
    xlim([-1000 1000])
    ylim([-500 1000])
    zlim([-10 10])
    
    %% plot the other timesteps
    for f = 2:length(Points)
        
        pause(TimeStep)
        
        MyGrid = horzcat( Points{1,f}.Position );
        
        m.XData = reshape([MyGrid(1,MyPoints(1,:));MyGrid(1,MyPoints(2,:));NaN(1,NPoint-1)],1,[]);
        m.YData = reshape([MyGrid(2,MyPoints(1,:));MyGrid(2,MyPoints(2,:));NaN(1,NPoint-1)],1,[]);
        m.ZData = reshape([MyGrid(3,MyPoints(1,:));MyGrid(3,MyPoints(2,:));NaN(1,NPoint-1)],1,[]);
        
    end
    
end

[Tiago Carvalho]

Hello,

Thank you so much! This is exactly what I wanted, I will read the code more carefully to see how to adapt to my larger script!

Thank you again.

Tiago

[Tiago Carvalho]

Sorry to bother again, is there a way to save this animation into a gif file? Or to reset the animation without having to run the whole code again?