Cycloid plates of golden age violins are closely modeled by curtate cycloid curves. Later work indicates that curtate cycloids do not serve as general models for these curves, which vary considerably. Cycloid A cycloid is the curve traced by a point on the rim of a circular wheel as the wheel rolls along a straight line without slipping. A cycloid is a specific form of trochoid and is an example of a roulette, a curve generated by a curve rolling on another curve. The cycloid, with the cusps pointing upward, is the curve of fastest descent under constant gravity, and is
Intersection curve has to fulfill the condition formula_29, because formula_28 has to be a tangent vector, which means any contour point is a point of the intersection curve of the two implicit surfaces For quadrics, formula_32 is always a linear function. Hence the contour line of a quadric is always a plane section (i.e. a conic section). The contour line of the surface formula_33 (see picture) was traced by the marching method. "Remark:" The determination of a contour polygon of a parametric surface formula_34 needs tracing an implicit curve in parameter plane. The intersection curve of two polyhedrons is a polygon (see