Circle plotting on different Planes

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Mazhar
Mazhar 2013-9-10
Hey,
I am trying to plot a series of 2D circle in a 3D plot, which are all on slightly different planes (orientated at different angles).
The information I have is;
Centers of the circles;
X = [2 4 5 7];
Y = [0 2 1 0];
Z = [1 3 5 7];
The radii for the circles are the same at 0.5 units.
When I plot these circles I want to see them orientated so that the normal from each circle is pointing in the direction of the next circle. In other words, the plane the circle is drawn on will be perpendicular to the line joining the centers.
the final picture would look like a small section of a pipe.
How could I achieve this?
All help is greatly appreciated.

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采纳的回答

Attila
Attila 2013-9-10
编辑：Attila 2013-9-10
Hi,
so your problem is more like math-related right?
If you already have the coordinates of the unoriented circle points, you should multiply them with the result of this, like
Rotated = Rx * Ry * Rz * original
(first circle with the first 3 matrices, etc):
clear all, close all, clc
X = [2 4 5 7];
Y = [0 2 1 0];
Z = [1 3 5 7];
r = 0.5
Coords = [X;Y;Z]
Coords_inc = Coords;
Coords_inc(:,3) = Coords(:,4) - Coords(:,3);
Coords_inc(:,2) = Coords(:,3) - Coords(:,2);
Coords_inc(:,1) = Coords(:,2) - Coords(:,1)
x = 1;
y = 2;
z = 3;
hold on
color = ['r' 'g' 'b' 'k'];
theta = -atan(Coords_inc(y,:)./Coords_inc(z,:)); % angle around x
phi = atan(Coords_inc(x,:)./Coords_inc(z,:));% angle 2 (y)
psi = atan(Coords_inc(y,:)./Coords_inc(x,:));% angle 3 (z)
for i=1:4
Rx = [1 0 0; 0 cos(theta(i)) -sin(theta(i)); 0 sin(theta(i)) cos(theta(i))]
Ry = [cos(phi(i)) 0 sin(phi(i)); 0 1 0; -sin(phi(i)) 0 cos(phi(i))]
Rz = [cos(psi(i)) -sin(psi(i)) 0; sin(psi(i)) cos(psi(i)) 0; 0 0 1]
t = 0:0.1:2*pi
x = cos(t)
y = sin(t)
z = zeros(1,length(t))
tol = [X(i); Y(i); Z(i)]
base = [x;y;z]
rotated = Rx*Ry*Rz*base
plot3(rotated(1,:)+X(i),rotated(2,:)+Y(i),rotated(3,:)+Z(i), color(i))
axis equal
end
This code snippet calculates the required orientations and then builds the required rotation matrices.
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Mazhar
Mazhar 2013-9-11
Ok so I think I kind of have it...almost.
Just finding it hard to understand one part of your code.
The rotation matrices you used (Rx, Ry, Rz), in your code, you have changed the sign (-/+) on the sin, to that given in other online sources: http://www.siggraph.org/education/materials/HyperGraph/modeling/mod_tran/3drota.htm
The graph produced by your code is the correct one, and if you replace the sign (-/+) on the sin, then the graph is not what I am looking for.
You have it correct, but I am wondering how you knew to change that?
Just want to understand your thinking behind it, so I can understand this better :D
Mazhar
Mazhar 2013-9-11
Got it to work :D
Thanks for your help!

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更多回答（2 个）

Matt J
Matt J 2013-9-10
You could start by plotting a prototype circle in the xy plane. Then roto-translate them in 3D using a transformation
R*points + t
where R is a 3x3 rotation matrix and t is a translation vector. This FEX file might help with that
http://www.mathworks.com/matlabcentral/fileexchange/30864-3d-rotation-about-shifted-axis
Finally, use scatter3() to plot the transformed points.
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Mazhar
Mazhar 2013-9-10
OK yeah, I see how it works now.
Is it possible for to create a code that will calculate the angel (rotation) required from the center points data??
Mazhar
Mazhar 2013-9-10
Also, If my circle does not have a set radius, but I have several radii data for each point of the data. How can I add in a loop to be able to plot such a circle (or shape, as it might not be completely circular)

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Grzegorz Knor
Grzegorz Knor 2013-9-10
编辑：Grzegorz Knor 2013-9-10
Try this code:
X = [2 4 5 7];
Y = [0 2 1 0];
Z = [1 3 5 7];
r = 0.5;
[x,y,z] = cylinder(r*ones(size(X)),100);
hold on
for k=length(X):-1:1
x(k,:) = x(k,:)+X(k);
y(k,:) = y(k,:)+Y(k);
z(k,:) = z(k,:)+Z(k);
h(k) = plot3(x(k,:),y(k,:),z(k,:),'r-');
direction = rand(1,3);
alpha = randi(90);
rotate(h(k),direction,alpha)
end
hold off
view(3)
axis equal
I've used random rotation directions and angles. Just calculate the proper values and replace in the code above.
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Grzegorz Knor
Grzegorz Knor 2013-9-10
First of all there is a small mistake, should be:
z(k,:) = Z(k);
instead of:
z(k,:) = z(k,:)+Z(k);
Each circle should be perpendicular to the line connecting its center point with the center point of the next circle, right? And what about last circle and its orientation?
Mazhar
Mazhar 2013-9-10
Almost, just the other way round.
The first circle should be horizontal (flat) and the corresponding circle should be perpendicular to the line joining its center and the one before.

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