5.1.9 Sor

Another version of a surface of revolution is the sor object. Its syntax is:

SOR:
  sor { NUM_POINTS, POINT_LIST [open] [SOR_MODIFIERS] }

SOR_MODIFIERS:
  [sturm [BOOL]] & [UV_MAPPING] & [OBJECT_MODIFIERS]

See also:

• [pov:6.5.1.12]Surface of Revolution
• [pov:3.4.2]Surface of Revolution Object
• www.f-lohmueller.de/.../sor1e.htm

This object is obtained by rotating the area between $y$-axes and the cubic polynomial from $P_{k}$ to $P_{k+1}$ through the points $P_{k-1}$, $P_k$, $P_{k+1}$ and $P_{k+2}$ around the $y$-axes. The point $P_0$ and $P_n$ are thus only control points.

See also:

• [pov:3.4.2]Surface of Revolution Object

Advantage of sor over lathe is that the intersection test for sor needs to solve a cubic polynomial whereas that for lathe needs to solve a polynomial of degree 6, which means quite a lot more work.