Generate the motion (Trajectory) of a sphere (or point) with given velocity value

Question

Alberto Acri 2024-8-21

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https://ww2.mathworks.cn/matlabcentral/answers/2146869-generate-the-motion-trajectory-of-a-sphere-or-point-with-given-velocity-value

回答： Madheswaran 2024-8-23

DATA.mat

Hi. I have this file 'DATA'. The first 3 columns are the nodes in space (X,Y,Z in [m]). The 4th column is not of interest. The fifth column is the velocity in [m/s].

Is it possible to visualize the motion (green direction) of a sphere (e.g., the red one in the figure) moving following the velocity values in the fifth column of DATA?

load("DATA.mat");
figure
plot3(DATA(:,1),DATA(:,2),DATA(:,3),'-k','LineWidth',0.1);
hold on
plot3(DATA(1,1),DATA(1,2),DATA(1,3),'r.','MarkerSize',30);
hold off
axis equal
xlabel('x')
ylabel('y')
zlabel('z')
grid off

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Answer 1

Aquatris 2024-8-21

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2146869-generate-the-motion-trajectory-of-a-sphere-or-point-with-given-velocity-value#answer_1502694

编辑：Aquatris 2024-8-21

在 MATLAB Online 中打开

data.mat

If you dont care about the actual timing and things, here is one way where the colors of the path indicate the speed and a simple animation show the full motion:

load('data.mat')

x = [DATA(:,1);nan];

y = [DATA(:,2);nan];

z = [DATA(:,3);nan];

v = [DATA(:,5);nan];

l = length(x);

figure(1)

for i = 1:1 % change it to 1:l to animate

clf

colormap(winter)

patch(x,y,z,v,'Facecolor','none','EdgeColor','interp')

colorbar

view(150,15)

grid on

grid minor

hold on

plot3(x(i),y(i),z(i),'ro','MarkerSize',15)

hold off

pause(0.1)

end

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Alberto Acri 2024-8-21

在 MATLAB Online 中打开

newData_SEL_cell.mat

Thank you. It might be helpful. If I would like to display multiple 'DATA' matrices present in a cell 'newData_SEL_cell' how can I display the trends simultaneously in the same figure?

I've tried a for loop but it doesn't seem to work the way it's supposed to. Suggestion?

load('newData_SEL_cell.mat')
figure
for S = 1:height(newData_SEL_cell)
    DATA = newData_SEL_cell(S,1);   % 1 e 50
    DATA = cell2mat(DATA);
    
    x = [DATA(:,1);nan];
    y = [DATA(:,2);nan];
    z = [DATA(:,3);nan];
    v = [DATA(:,5);nan];
    l = length(x);
     
    %figure
    for i = 1:l % change it to 1:l to animate 
        clf
        colormap(winter)
        patch(x,y,z,v,'Facecolor','none','EdgeColor','interp')
        colorbar    
        view(150,15)
        grid off 
        %grid minor
        hold on
        plot3(x(i),y(i),z(i),'ko','MarkerSize',2)
        plot3(x(i),y(i),z(i),'ko','MarkerSize',1)
        plot3(x(i),y(i),z(i),'ko','MarkerSize',3)
        hold off
        axis equal
        pause(0.1)
    end
end

Aquatris 2024-8-21

编辑：Aquatris 2024-8-21

在 MATLAB Online 中打开

newData_SEL_cell.mat

Assuming each row happens at the same time:

load('newData_SEL_cell.mat')

% get x,y,z,v as cell arrays

x = cellfun(@(x) {[x(:,1);nan]},newData_SEL_cell);

y = cellfun(@(x) {[x(:,2);nan]},newData_SEL_cell);

z = cellfun(@(x) {[x(:,3);nan]},newData_SEL_cell);

v = cellfun(@(x) {[x(:,5);nan]},newData_SEL_cell);

% maximum number of data points in the whole data set

L = max(cellfun(@(A) length(A),x));

figure(1)

% loop through data points

for i = 1:1 % change it to 1:(L-1) to animate

clf

for j = 1:length(x) % loop through data sets

colormap(winter)

patch(x{j},y{j},z{j},v{j},'Facecolor','none','EdgeColor','interp')

colorbar

view(150,15)

grid on

grid minor

hold on

% because the 3 datasets are not the same length we need to check

if (length(x{j}) >= i) % check if we are not at the end point

plot3(x{j}(i),y{j}(i),z{j}(i),'ro','MarkerSize',15)

else

% (end-1) cause last element we put a 'nan' to prevent unnecessary

% connection between last point and first point during 'patch'

plot3(x{j}(end-1),y{j}(end-1),z{j}(end-1),'ro','MarkerSize',15)

end

hold off

pause(0.1)

end

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Answer 2

Madheswaran 2024-8-23

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2146869-generate-the-motion-trajectory-of-a-sphere-or-point-with-given-velocity-value#answer_1503904

在 MATLAB Online 中打开

Hello,

The data appears somewhat unclear, as it specifies the object's velocity only at certain spatial positions, necessitating some assumptions. Here is the assumption made regarding the object's velocity in the intermediate position between the position mentioned in any two rows:

For the space between DATA(i, 1:3) and DATA(i+1, 1:3), the object is assumed to moving at a constant velocity as described in DATA(i, 5).

Below is a simple script to visualize the object's movement using a loop:

load DATA.mat
figure
plot3(DATA(:, 1), DATA(:, 2), DATA(:, 3));
% changing the aspect ratio and view to get the similar view as the posted image
pbaspect([1 1 4])
view([154.8 19.8])
ln = size(DATA, 1);
time_unit_divisor = 10;
hold on
pt = plot3(DATA(1, 1), DATA(1, 2), DATA(1, 3), 'r.', 'MarkerSize',30);
for i = 2:ln
    distance = norm(DATA(i, 1:3) - DATA(i-1, 1:3));
    velocity = DATA(i-1, 5);
    time_taken = distance/velocity;
    adjusted_time = time_taken/time_unit_divisor;
    
    pause(adjusted_time);
    
    %update the new position
    pt.XData = DATA(i, 1);
    pt.YData = DATA(i, 2);
    pt.ZData = DATA(i, 3);
end
hold off

The above code would produce the plot like this:

You can adjust the speed of the animation by modifying the ‘time_unit_divisor’ variable. To enhance the smoothness of the animation, consider plotting additional points within each iteration by interpolating the intermediate positions of the object.

Hope this answers your question!

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Generate the motion (Trajectory) of a sphere (or point) with given velocity value

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Generate the motion (Trajectory) of a sphere (or point) with given velocity value

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