Not flat shapes like circles and squares, but solid shapes like cubes and cones ... GIRL 1: Now the next shape is a sphere. Try to make yourself into a sphere – a big ball!

[DaveMakesStuff] demonstrates a great technique for 3D printing a sphere; a troublesome shape for filament-based ... at a higher temperature to ensure solid bonding between each layer.

The nine chapters deal respectively with preliminary ideas, trihedral angles, skew quadrilaterals, tetrahedra, transversals, oblique cones, spheres, inversion, and recent geometry of the tetrahedron.