# How to rotate a rectangle

20 views (last 30 days)
Nathan Batta on 18 Feb 2020
Edited: darova on 19 Feb 2020
Hello!
I am working on modeling a dynamic suspension system and I am trying to create an animation for it. I have the translation components completed and working fine but I need to rotate a rectangle and for some reason it is not working.
I used the below code to create the rectangle and rotate it 45 degrees about the z axis:
rotate(rectangle('Position',[x_left,xc-height/2+2*mass_height_diff,w_chassis+1,height],'EdgeColor','black'),[0 0 1],45)
However, running the code shows the rectangle moving up and down as it should but not rotating at all. Does anyone know what the issue is here? Thank you!

darova on 18 Feb 2020
If you open (Ctrl+D) rotate function you will find these lines at the end:
if strcmp(t,'surface') || strcmp(t,'line')
set(h(i),'xdata',newx,'ydata',newy,'zdata',newz);
elseif strcmp(t,'patch')
set(h(i),'Vertices',[newx,newy,newz]);
elseif strcmp(t,'text')
set(h(i),'position',[newx newy newz])
elseif strcmp(t,'image')
set(h(i),'xdata',newx,'ydata',newy)
end
When you draw a rectangle
h = rectangle('Position',[x_left,xc-height/2+2*mass_height_diff,w_chassis+1,height],'EdgeColor','red');
get(h,'type')
ans =
rectangle
As you can see there is no case for rectangle. Maybe that is way rotate didn't work
So i used simple plot
x_left = 3;
xc = 1;
height = 2;
mass_height_diff = 5;
w_chassis = 1;
height = 5;
x = [x_left
w_chassis+1];
y = [xc-height/2+2*mass_height_diff
height];
h = plot([x(1) x(2) x(2) x(1) x(1)],...
[y(1) y(1) y(2) y(2) y(1)]);
rotate(h,[0 0 1],45)

Nathan Batta on 19 Feb 2020
I'm not sure why it is saying that but I definitely have them both named h.
darova on 19 Feb 2020
What happens if you try
h = plot([x(1) x(2) x(2) x(1) x(1)],...
[y(1) y(1) y(2) y(2) y(1)]);
h1 = get(h,'children');
rotate(h1,[0 0 1],45)
darova on 19 Feb 2020
Maybe rotate manually?
x = [x_left
w_chassis+1];
y = [xc-height/2+2*mass_height_diff
height];
x = x([1 2 2 1 1]);
y = y([1 1 2 2 1]);
a = 15;
R = [cosd(a) -sind(a);sind(a) cosd(a)]; % rotation matrix
v = R*[x(:)-mean(x) y(:)-mean(y)]'; % center and rotate rectangle
x = v(1,:)+mean(x); % restore original position
y = v(2,:)+mean(y);
plot(x,y,'k');
EDITED: rotation matrix

Nathan Batta on 19 Feb 2020
Update:
I was able to get it to work using the following code:
g=hgtransform;
r=rectangle('Parent',g,'Position',[x_left,xc+2*mass_height_diff,w_chassis+1,height],'EdgeColor','black','LineWidth',.75);
g.Matrix=makehgtform('zrotate',theta);
However, is there a way to get it to rotate about the center of the rectangle? Right now it is rotating about the bottom left corner I believe. Thank you!