Hi, I am using levelplot() to plot a primary response surface, z1. I wish to write a custom panel function that will let me plot another surface z2 = f(x,y) over z1. The second surface z2 is either NA or 1, and at locations where z2 = 1, I will use a color with low alpha to let the the z1 surface show through. How can I do this? Regards, Scott Waichler Pacific Northwest National Laboratory Richland, WA USA