This screenshot shows a JOGL application displaying a 128x128 heightmap, but with a little twist. Instead of each pixel giving the height of 1 vertex, a pixel defines the height of 4 vertices. That means I need extra quads just to weld everything together. I added the extra quads in one direction, but not in the other. You get "slices" of land!
The effect is funny, but not the least bit natural, because of the lack of sloped surfaces. Back to the drawing board :-)

However, drawing 128x128x3 quads, each containing 4 vertex coordinates and texture coordinates, is still running smoothly. I like "smooth"!