Date: Dec 7, 2012 1:37 AM
Author: Roger Bagula
Subject: tubes program not working in version 9
The problem seems to be sometimes it works but mostly it doesn't.

The tubes program was written for an earlier version

( works in version 5 I think) by Mark McClure

and has worked fine for literally years.

I haven't got a clue what has gone wrong.

( technically these are called channel surfaces or the like).

TubePlotFrenet[curve_List, {var_, min_, max_}, radius_, opts___] :=

Module[{tangent, unitTangent, normal, unitNormal, biNormal},

tangent = D[curve, t];

unitTangent = tangent/Sqrt[tangent.tangent];

normal = D[unitTangent, t];

unitNormal = normal/Sqrt[normal.normal];

biNormal = Cross[unitTangent, unitNormal];

ParametricPlot3D[

curve + radius Cos[s] unitNormal + radius Sin[s] biNormal //

Evaluate, {var, min, max}, {s, 0, 2 \[Pi]}, opts]]

r = Cos[q0*t] + 2;

x = r* Cos[p0*t];

y = r *Sin[p0*t];

z = Sin[q0*t];

w0 = 8*{x, y, z}

h = TubePlotFrenet[w0, {t, 0, 2 \[Pi]}, 1, Axes -> None,

Boxed -> False, PlotPoints -> {64, 16},

ColorFunction -> "CandyColors", MeshFunctions -> {#3 &}]

My other tubes program which came from an answer in this group

still works.