No, I assure you algorithms are NOT patentable under U.S. law. Your example proves my point - the algorithm is NOT claimed in the patent. The patent covers a SYSTEM, not an algorithm.
While I have no problem with software patents, I do have to disagree here. The "marching cube" patent included a method claim. An "algorithm" is just a fancy way of saying a "computer implemented method." If you patent a method that is implemented on a computer, you have patented the algorithm.
What's interesting about the "marching cube" patent identified at the link is the discussion of how people came up with another approach to get around the patent. The "marching tetrahedrons" approach actually resolved some problems with the "marching cubes" approach. This is exactly what the patent laws are meant to do -- you disclose an idea and get a limited monopoly for that invention, and then others can improve on your idea.
Software is copyrightable, but it is also patentable. Software is not, as others have said, just "math." Software is instructions for causing a computer to do something. It might rely on math, but it is a process -- store this data, use that data, display this, receive input from that. The Supreme Court just recently ruled that some business methods might be patentable, and it refused to rule that all business methods are unpatentable. In light of that, it is unlikely that the Supreme Court would rule that software, which is much more useful than business methods, is unpatentable.