How calculate the points inside the square and triangle?

I did calculate the points (scatteres) located inside the circle as presented in the code. I'm wondering how I can do it for square and triangle?

I cannot find proper tag for this question.

 Phantom.x_size = 50/1000;   %  Width of phantom [mm]
Phantom.y_size = 10/1000;   %  Transverse width of phantom [mm]
Phantom.z_size = 60/1000;   %  Height of phantom [mm]
Phantom.z_start = 30/1000;  %  Start of phantom surface [mm];
N = Calculate_number_of_scatterers(Phantom);
N = 1000*ceil(N/1000);
%  Create the general scatterers
x = (rand (N,1)-0.5)*Phantom.x_size;
y = (rand (N,1)-0.5)*Phantom.y_size;
z = rand (N,1)*Phantom.z_size + Phantom.z_start;
%  Generate the amplitudes with a Gaussian distribution
amplitudes = randn(N,1);
%Make the cyst
r  = 15/2/1000;     %radius of cyst[mm]
xc = 10/1000;       %place of the cyst
zc = 40/1000 + Phantom.z_start;
inside = ( ((x-xc).^2 + (z-zc).^2) < r^2);  % scatteres inside the cyst
amplitudes = amplitudes .* (1-inside);      % amplitude of the scatteres inside the cyst
Phantom.positions = [x y z];
Phantom.amplitudes = amplitudes;
figure; plot3(Phantom.positions(:,1), Phantom.positions(:,3),Phantom.amplitudes,'.')

[Neda Azarmehr]

Sorry, I forgot to attache these.

Answer 1

[KSSV]

Read about inpolygon. This function will give you indices of the points lying inside a polygon.

[Neda]

thank you for the comment, it's true, but it inpolygon didn't solve my issue. I used

[in,out] = inpolygon(xc,zc,x,z);

amplitudes = amplitudes .* (1-in);% amplitude of the scatteres inside the cyst

[Image Analyst]

You forgot to include Calculate_number_of_scatterers() so we can't do much. Give us code that at least runs and demonstrates why inpolygon() does not solve your problem.