Stereographic projection

thingiverse

In Fig 3.12 of Visualizing Mathematics via 3D Printing, the model demonstrates stereographic projection, where points on the sphere are mapped to corresponding points on the plane using imaginary lines from the north pole. This concept is also simulated by a light source positioned at the sculpture's north pole, with shadows casting as straight lines on a plane representing the projection. You can find this projection technique on Shapeways, and an updated version of the file includes a wider base for easier printing.