A Rope Macro for creating a twisted rope that follows a spline.
The macro gives you control of the spline path, the number of strands, the rate of twist, and the fatness of the strands.
The output is mesh2 object with support for uv_mapping.
In the example scene, I've made use of the uv_mapping to use a gradient pattern to suggest that the five main strands
of this rope are made from a large number of finer threads.
There are two versions of the rope macro: Rope.inc and Rope2.inc which use different algorithms for calculating the surface.
Each of them have problems with certain splines. For most purposes "Rope.inc" produces a slightly better result, but
it doesn't work wtih splines that pass through the vertical.
If you get an ugly pinch point in your rope then switch to "Rope2.inc"
and see if that's any better.
3-Mar-2005: Now accepts an optional Filename to which the calculated mesh data can be written.
If the file aleady exists, the macro will read it back.