General quadrics
Degenerate quadrics
- planes (no quadratic terms),
- pairs of parallel planes (e.g. x2 - 1 = 0)
- pairs of intersecting planes ( e.g. x2-1 = 0)
- elliptic cylinders (e.g. x2+z2-1=0)
- hyperbolic cylinders (e.g. x2-z2-1=0)
- parabolic cylinders (e.g. x2 -z = 0)
Possible to get “imaginary” surfaces (that is, with no points)! Example: x2 + 1 = 0