Spherical Sketch Pad Routines

• Setting up the coordinate system
  A data coordinate system must be set up before using these routines.

• Setting the sphere position and orientation
  A sphere may be oriented in any way. Multiple orientations and sizes are easy. Multiple spheres may be positioned at any locations.

• Drawing Latitude, Longitude, and Radial lines
  Three basic routines are used to draw along the three spherical coordinate directions.

• Clipping and hidden lines
  Some lines may be visible, others hidden. It is easy to control this.

• Writing text on a sphere
  Text may be written on the surface of a sphere. It may be oriented at a specified angle.

• Plotting curves and points on a sphere
  Curves and points may be plotted on a sphere or above or below the surface.

• A gallery of interesting plots
  A number of interesting plots are shown. The algorithms used to make them are listed and discussed. Some may even be useful.