ISo-Surface
			The Iso-Surface series is very similar to a TSurfaceSeries. It draws a 3D XYZ mesh of X by Z regular-spaced grid elements using the Y value as elevation value. The difference between a Surface and Iso-Surface series is that Iso-Surface fills each "cell" in a different way to Surface. Surface series simply paints the interior of a cell using a calculated color based on each cell Y value. Iso-surface, in contrast, fills each cell with "horizontal" bands of multiple colors depending on the cell slope and the number of palette colors.