Clicking the links below will lead you to important information about 3D spline charts:
About 3D Spline Charts — Gives you a brief description of 3D spline charts, and explains why you would want to use them.
Working with 3D Spline Chart Data — Provides information on the type of data necessary to generate 3D spline charts (e.g., number of numeric columns), as well as how data is mapped to it.