Surf plots each grid line, as a BLACK line. The black lines are useful, and help you to see the shape of the surface for smaller grids. But they are a problem if you have too many lines. If you have a LARGE array to plot, then the black lines dominate what you see, and you see nothing but black. For example:
Z = rand(500,500);
surf(Z)
But we also can plot it without the grid lines.
surf(Z,'edgecolor','none')
