How would you calculate the volume of a large boulder?

Say you have a large-ish boulder, about the size of a truck, and you want to calculate the volume of rock. Field procedure is not relevant, end result is that you have a few hundred 3D points on the surface of this irregular shape with dents and knobs and what not. I'm sure point cloud software handles this, but I'm wondering about typical survey software in CAD, personally using Microsurvey CAD.

I can't see a way of doing this other than slicing the object into two halves, creating two surfaces, and then calculate volumes for each half, top and bottom. Unless I'm mistaken, I don't believe it's possible to create a closed potato-like volume shape with the modeling algorithms as implemented by Microsurvey, or Carlson I suspect.

Anyways, anybody ever done something similar? What did you end up doing?

Thanks.