Hi Victor,
You can detect a collision between the ball and the cylinder if the distance between the center of the ball and the outside of the cylinder is less than or equal to the radius of the ball.
To do that, you will need to increase the number of points along the circumference of the cylinder such that the gap between the points is less than the radius of the ball.
I have modified your code below to show an example of how to detect collisions:
Obj = [0 0 0];
velocity = [2e-8 2e-8 2e-8];
r = 5e-7;
radius = 5e-8;
for i = 1:20
clf
N = ceil(2*pi*r/radius);
[X,Y,Z] = cylinder(r,N);
h = 20e-7;
Z = Z*h-2*r;
cyl = surf(X+0.5e-6,Y,Z,'FaceColor','none');
rotate(cyl, [0 1 0], 90)
hold on
[x,y,z] = sphere;
plot3(radius*x+Obj(1,1),radius*y+Obj(1,2),radius*z+Obj(1,3),'k');
xlabel('x')
ylabel('y')
zlabel('z')
Obj = Obj + velocity;
view([-30,6])
set(gca,'xlim',[-5e-7 15e-7])
set(gca,'ylim',[-10e-7 5e-7])
set(gca,'zlim',[-1e-6 1e-6])
drawnow
displacements = Obj(2:3)-[cyl.YData(1,:) cyl.YData(2,:);cyl.ZData(1,:) cyl.ZData(2,:)]';
distances = vecnorm(displacements,2,2);
collision = any(distances <= radius);
if collision
fprintf('Collision occurred on iteration %g',i);
break;
end
end
As far as updating the velocity after that point, it is up to you which method you wish to use for the update.
