Another idea would be to use one or two flat planes, and then put a "beaded curtain" material on the planes. If you have a good modeling program, you could drape the planes however you want. Transparency mapping would make the space between the beads see-through. That is the best way to keep the size down; otherwwise, like everyone said, your model will get horrifically large. Wish I could point you to the right material, but I haven't seen one like that yet. Might not be hard to build though, if you have a good paint program. Just draw 6-10 beads on a string, and then replicate a lot. Seems like the material would be straight and the 3d aspects would come from how you put ripples and curves in the object itself. Or you could model 6-10 spherical and ovoid shapes in a modeling program; render them out, and use them as the bead models in your paint program. Hope PhilC solved your problem and you're already rendering!