From my understanding you want to find all the cells in a 3D matrix which is intersected by an 3D line (given vertical angle and azimuth). You could convert spatial coordinates to cartesian coordinate to map it with the 3D matrix and then make small increments to find all the cells in the matrix that are in your path (with some conditions). Here is a simple script that might be helpfull.
A = zeros(3, 3, 3);
teta = pi/10; % vertical angle
phi = pi/6; % azimuth
smallstep = 1; % you can make it smaller for more precision eg:0.5
for r = 0:1:3
x = r*sin(teta)*cos(phi);
y = r*sin(teta)*sin(phi);
z = r*cos(teta);
if A(round(x),round(y),round(z)) == 0: % any condition that you need
disp([round(x) round(y) round(z)]);
end
end
