Generating randomly distributed cylindrical fibers in 3D

Hello,

I am trying to Generate a 3D structure with randomly distributed cylindrical fibers. I would appreciate any help or any code that help me to have a quick start.

Thanks, Hamed

[Walter Roberson]

Oriented along any particular axis, or randomly oriented?

Overlapping permitted or not?

Constant length?

Is there a maximum interior gap size that "must" be filled? Is there a minimum distance between adjacent cylinders ?

[Abdolrasol Rahimi]

Thank you Walter for the response.

Here are my answers to your questions: It would be great if I have both options of preferred orientation and totally random.

Overlapping is not permitted, but fibers touch each other.

Length can vary, but I want all of the fibers to be limited to a hypothetical cylinder.

Yes. I want to be able to change the percentage of interior space that is filled with cylinders. No minimum distance between cylinders.

I have attached some scanning electron microscopy which gives a better vision. The red arrow showing two fibers in contact.

Thank you for your help.

[Walter Roberson]

My browser is saying those .jpg contain errors :(

[Abdolrasol Rahimi]

Hi Walter,

I am sorry I thought that I posted the new version of images, but it seems not. Sorry for late response.

I have attached the new version of images. Please let me know if it works for you.

Answer 1

[KSSV]

With the below code..you can draw a cylinder of given radius and height....ans also you can rotate this cylinder to any arbitrary angle.

% Units are considered in MKS system
Radius = 0.1 ;           % Radius of the cylindrical shell
theta = 360. ;           % Angle of the Cylinder
Height = 20. ;           % Height of the Cylinder
%
NH = 20 ;                % Number of Elements on the Height
NT = 50 ;               % Number of Angular Dicretisation 
%
nel = NH*NT ;           % Total Number of Elements in the Mesh
nnel = 4 ;              % Number of nodes per Element 
% Number of points (nodes) on the Height and Angluar discretization
npH = NH+1 ;
npT = NT+1 ;
nnode = npH*npT ;       % Number of nodes
% Discretizing the Height and Angle of the cylinder
nH = linspace(0,Height,npH) ;
nT = linspace(0,theta,npT)*pi/180 ;
[H, T] = meshgrid(nH,nT) ;
% Convert grid to cylindrical coordintes
X = Radius*cos(T); 
Y = Radius*sin(T);
Z = H ;
surf(X,Y,Z) ;
% axis equal
% axis([-5 5 -5 5 -10 10])
%%Rotate cylinder
% set up rotation matrix:
theta = 90;   % angle in degrees 
theta = theta* pi/180;
R = [cos(theta) 0 sin(theta); 0 1 0; -sin(theta) 0 cos(theta)];

% get points at the two rings and rotate them separately:
P = [X(:) Y(:) Z(:)] ;
Q = P*R;
% reassemble the two sets of points into X Y Z format:
X1 = reshape(Q(:,1),npT,npH) ;
Y1 = reshape(Q(:,2),npT,npH) ;
Z1 = reshape(Q(:,3),npT,npH) ;

figure;
surf(X1,Y1,Z1);

[Abdolrasol Rahimi]

Thank you for the answer. The code is written nicely. I tried to modify the code to have a solid cylinder instead of being hollow, but I was not successful. How can I change it to have a solid cylinder?

Answer 2

[Gabriel Gaal]

Hi KSSV,

I am trying to use your code, and despite the fact it generates a hollow cylinder, it does not rotate under a arbitrary angle. This code only works for 90, 180, 270 and 360. I am trying to fix it but I am new at MatLab and I having a hard time to doing it. Can you spare a few more thoughts on it?

[amira soliman]

can you please help me to do that if you have a solution because i am trying to have a code to draw randomly oriented fiber in a box

[Walter Roberson]

Create a cylinder in fixed coordinates, and then apply a general rotation matrix to the coordinates

https://en.wikipedia.org/wiki/Rotation_matrix#General_rotations

RA = rand(1,3) * 2*pi;
M = makehgtform('xrotate', RA(1), 'yrotate', RA(2), 'zrotate', RA(3));
XYZ0 = [X1(:), Y1(:), Z1(:), zeros(numel(X1),1)];
RXYZ0 = XYZ0 * M;   %matrix multiplication
X1R = RXYZ0(:,1);
Y1R = RXYZ0(:,2);
Z1R = RXYZ0(:,3);