Hi there, Here is my problem : I'm trying to represent ( and animate ) the surface of a vibrating circular drum using plot3d. Let O be the center of the drum, the function "u" I found gives the height (z) of a point on the drum located at a distance r from O at t ( time ) in cylindrical coordinates ( u does not depend on theta). So what I'm basically trying to do is to plot the surface given by the equation z = u(r,t). So far I've failed to do so using plot3d. Could someone here help me with this ? Any help will be greatly appreciated ! Thank you. Tiilt