gleHelicoid - Generalized torus, spiral with circle contour.

rToroid   circle contour (torus) radius

       startRadius
                 spiral starts in x-y plane

       drdTheta  change in radius per revolution

       startZ    starting z value

       dzdTheta  change in Z per revolution

       startXform
                 starting contour affine transformation

       dXformdTheta
                 tangent change xform per revolution

       startTheta
                 start angle in x-y plane

       sweepTheta
                 degrees to spiral around

       Linas Vepstas (linas@linas.org)

GLE                                                    3.0                                     gleHelicoid(3GLE)

       Generalized Torus. Similar to gleSpiral, except contour is a circle.  Uses gleSpiral to draw.

       gleHelicoid - Generalized torus, spiral with circle contour.

       gleSpiral, gleToroid

       void gleHelicoid (gleDouble rToroid,
                         gleDouble up[3],
                         gleDouble startRadius,
                         gleDouble drdTheta,
                         gleDouble startZ,
                         gleDouble dzdTheta,
                         gleDouble startXform[2][3],
                         gleDouble dXformdTheta[2][3],
                         gleDouble startTheta,
                         gleDouble sweepTheta);