3D Equation of the Month. 
from House Of 3D .com 

Welcome to the only website that puts a different 3D equation up on a 3dimensional pedestal each month so you can spin it around. Come back next month for an exciting new 3D equation graph. You can start the graph spinning by gently dragging on it with your mouse and releasing. If you have 3D specs, you can use those, too. You can see this and a lot more 3D equation graphs on my 3D Graph Applet!
This month's equation, y = x^4  z^4, strongly resembles the equation y = x^2  z^2. They are both from the hyperbolic paraboloid family, commonly referred to as 'saddles'. This equation differs from its '^2' cousin in that it is flatter on the 'seat' part, and suddenly begins to climb very steeply. This is a reflection of n^4's property of being very close to 0 when less than 1, and very, very large when greater than one. If you have a special favorite 3D equation that doesn't already appear on my 3D Graph Applet, you can audition it for 3D Equation of the Month by emailing it to me. Please have at least one axis free from multiple solutions. An actual graph is not necessary. S t e r e o s c o p i c ViewMaster T r i b u t e ! 3D Fractal generator. Updated December 2, 1997 