Rotate geometry at one specified point

Hi,

I wanted to rotate the inner rectangle (only) to 45 degree, which (p1(1),p1(2)) as the fixed point as rotation. I am not sure how to do it by the coordinates - the points are the same as before. This is my code:

function Nano_Sphere_Dat_Generator
clear
clc
clf
%set value of geometric parameters
a=0.0;  
b=0.0; 
c=1000;  
plate_length=30000;  
plate_width=1000;  
pos_CNN=10000;        
channel_length=100000;  
channel_width=60000;      
upstream_dist=30000;       
CNN_width=0.001;          
%create the outer boundary
p1(1)=a-upstream_dist;
p1(2)=-channel_width/2;
p2(1)=a-upstream_dist+channel_length;
p2(2)=-channel_width/2;
p3(1)=a-upstream_dist+channel_length;
p3(2)=channel_width/2;
p4(1)=a-upstream_dist;
p4(2)=channel_width/2;
plot([p1(1),p2(1)],[p1(2),p2(2)])
hold on
plot([p2(1),p3(1)],[p2(2),p3(2)])
plot([p3(1),p4(1)],[p3(2),p4(2)])
plot([p4(1),p1(1)],[p4(2),p1(2)])
axis equal
%create the plate geometry
p5(1)=a;
p5(2)=b;
p6(1)=a+pos_CNN;
p6(2)=b;
p7(1)=a+pos_CNN+CNN_width;
p7(2)=b;
p8(1)=a+plate_length;
p8(2)=b;
p9(1)=a+plate_length;
p9(2)=b-plate_width;
p10(1)=a
p10(2)=b-plate_width;
x = [p6(1) p7(1) p8(1) p9(1) p10(1)];
y = [p6(2) p7(2) p8(2) p9(2) p10(2)];
h = scatter(x,y);
h1 = rotate(h,15,[0 0 0])
scatter(p5(1),p5(2))
scatter(p6(1),p6(2))
scatter(p7(1),p7(2))
scatter(p8(1),p8(2))
scatter(p9(1),p9(2))
scatter(p10(1),p10(2))

Answer 1

[Wan Ji]

Here I added the rotation method for you

function Nano_Sphere_Dat_Generator
clear
clc
clf
%set value of geometric parameters
a=0.0;  
b=0.0; 
c=1000;  
plate_length=30000;  
plate_width=1000;  
pos_CNN=10000;        
channel_length=100000;  
channel_width=60000;      
upstream_dist=30000;       
CNN_width=0.001;          
%create the outer boundary
p1(1)=a-upstream_dist;
p1(2)=-channel_width/2;
p2(1)=a-upstream_dist+channel_length;
p2(2)=-channel_width/2;
p3(1)=a-upstream_dist+channel_length;
p3(2)=channel_width/2;
p4(1)=a-upstream_dist;
p4(2)=channel_width/2;
plot([p1(1),p2(1),p3(1), p4(1), p1(1)],[p1(2),p2(2),p3(2),p4(2),p1(2)],'r-')
hold on
axis equal
%create the plate geometry
p5(1)=a;
p5(2)=b;
p6(1)=a+pos_CNN;
p6(2)=b;
p7(1)=a+pos_CNN+CNN_width;
p7(2)=b;
p8(1)=a+plate_length;
p8(2)=b;
p9(1)=a+plate_length;
p9(2)=b-plate_width;
p10(1)=a;
p10(2)=b-plate_width;
% Here is how to rotate
x = [p5(1),p6(1) p7(1) p8(1) p9(1) p10(1)]; 
y = [p5(2),p6(2) p7(2) p8(2) p9(2) p10(2)];
xr = x - p1(1);
yr = y - p1(2);
theta = 45 * pi /180; % rotate with 45 degrees
xrot = xr*cos(theta) - yr*sin(theta) + p1(1);
yrot = xr*sin(theta) + yr*cos(theta) + p1(2);
scatter(x,y,'g'); % before rotation
scatter(xrot,yrot,'c'); % scatter the points after rotate
legend('plate boundary', 'before rotation','after rotation')

The figure becomes

[ka chun yick]

Thanks, if i wanted to rotate around (p10(1), p10(2)) as a reference fixed point as rotation - not the origin this time. I have changed the code: But the results seems not alright

xr = x - p10(1);
yr = y - p10(2);

[Adam Danz]

+1

An alternative method that uses the values stored in the scatter handle,

h = scatter(x,y);
zRotMat = @(th)[cos(th) -sin(th); sin(th) cos(th)];
xyRot = zRotMat(45*pi/180) * ([h.XData; h.YData]-p1(:)) + p1(:);
set(h, 'XData', xyRot(1,:), 'YData', xyRot(2,:))

[Wan Ji]

there are 2 place to change the code

xr = x - p10(1); 
yr = y - p10(2); 
theta = 45 * pi /180; % rotate with 45 degrees 
xrot = xr*cos(theta) - yr*sin(theta) + p10(1); 
yrot = xr*sin(theta) + yr*cos(theta) + p10(2);