How can I give a rotational velocity to spheres?

t = linspace(0,6,250);
x1 = 0;
x2=2.01;
y = 0;
z = 0.234778*t;
figh = figure;
for k=1:length(t)
clf
t_k = t(k);
z_k = z(k);
[X,Y,Z] = sphere;
X2 = X ;
Y2 = Y ;
Z2 = Z ;
s=surf(X2,Y2,Z2+z_k);
hold on
[X,Y,Z] = sphere;
X2 = X;
Y2 = Y;
Z2 = Z;
sg=surf(X2+2.01,Y2,Z2+z_k);
grid on
xlabel('x')
ylabel('y')
zlabel('z')
xlim([-2.7 3.2])
ylim([-2.8 2.5])
zlim([0 3.9])
title(['t = ',num2str(t_k)])
view([30 35])
movieVector(k) = getframe;
end

so, this is my code for two sphere located in xy plane translating in z direction, now i want the spheres to rotate about y axis with some constant speed, how can I do that? what lines of code I should add?

[ka]

@Matt JSorry I forgot to write hold on

check now!

Answer 1

[Matt J]

This uses AxelRot from the File Exchange (Download):

figh = figure;

%%Axes
ax = axes('XLim',[-4 4],'YLim',[-4 4],'ZLim',[-4 4]);
view(3)
grid on
xlabel('x')
ylabel('y')
zlabel('z')
axis vis3d

%Initial Spheres
[X,Y,Z] = sphere;
s(1)=surface(X,Y,Z);
s(2)=surface(X+2.01,Y,Z);

%%Transformers
T1=hgtransform('Parent',ax);
T2=hgtransform('Parent',ax);
s(1).Parent=T1;
s(2).Parent=T2;

%Movie parameters
theta = linspace(0,360,250); 
K=numel(theta);
movieVector(K)=struct('cdata',[],'colormap',[]);  %pre-allocate

%%Draw
for k=1:K

    T1.Matrix=AxelRot( theta(k), [0,1,0]);
    T2.Matrix=AxelRot( theta(k), [0,1,0],  [2.01,0,0]);

    drawnow
    movieVector(k) = getframe;
end

[ka]

In this case both spheres are rotating on same axis

but I want both spheres to rotate about y axis going through their centre so their motion won't be coupled.

Thanks

[Matt J]

I've modified the code accordingly. You will need to get AxelRot from the File Exchange,

https://www.mathworks.com/matlabcentral/fileexchange/30864-3d-rotation-about-shifted-axis/?s_tid=LandingPageTabfx

[ka]

Thankyou, for the help.

As I mentioned in the problem the spheres are translating also in z direction with some constant velocity(along with the rotation about y axis ). what should be added to implement that?

[Matt J]

Something like this,

z = linspace(0,6,K);
for k=1:K
    
    Mz=makehgtform('translate',[0,0,z(k)]);
    
    T1.Matrix=Mz*AxelRot( theta(k), [0,1,0]);
    T2.Matrix=Mz*AxelRot( theta(k), [0,1,0],  [2.01,0,0]);
    
    drawnow
    
    movieVector(k) = getframe;
    
end

[ka]

THANKS @Matt J!