what program can trim 3d terrain model to the boundaries of a custom vector shape?

Hey guys, I'm really struggling to figure out what I thought would be a simple problem. I have a 3D terrain model I'd like to print. It is currently a rectangle but I would like to use a custom vector shape (organic shape I make in illustrator) to crop the model so that all the area outside of that custom shape is removed? Think taking a square model and cropping it into a circle shape instead... I'm trying to find a way to use a custom vector as a cutting tool for the model but can't figure out how to do this is Meshmixer or any other slicing software. I want a way to import a vector file, size it and line it up with the model and then remove all the model that falls outside of that shape. Make sense?Any help is very appreciated!