Well, the effect is to me unclear, too. ;-) But it works. About the primitives: Take two cylinders, one positive, one negative. Make the negative one a bit smaller than the positive one. Boolean them together. You get a hollow cylinder. Take two spheres and do the same again. You get a hollow sphere. Make the booleaned group positive, add a negative cube which deletes the lower half of the booleaned sphere. So you get a half, hollow sphere. Put the sphere and the cylinder together and you get something like a "test tube". Place it onto the ground, duplicate it as often you like and put light in it like shown above. Apply the mentioned settings and voil light beams. Don't ask me "why" it works. I told you "how" you can do it. ;-)) J.