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I've beein trying to solve this problem but somehow I just can't combine Manipulate and ParametricPlot3D.

trobrid[g_, t_, a_, b_] := Module[{X, Y, Z, tang, norm, binorm, k, l},
g == {X[t], Y[t], Z[t]};
tang = D[g, t]/Simplify[Sqrt[D[g, t].D[g, t]]];
norm = D[tang, t]/Simplify[Sqrt[D[tang, t].D[tang, t]]];
binorm = FullSimplify[Cross[tang, norm], t > 0];
Manipulate[
   ParametricPlot3D[g, {t, a, b}],
   Graphics3D[{
       Red, Arrow[{g, tang + g} /. {t -> s}],
       Blue, Arrow[{g, norm + g} /. {t -> s}],
       Purple, Arrow[{g, binorm + g} /. {t -> s}]
 }], {s, a, b}]
]

This is the error:

enter image description here

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1 Answer 1

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Try this:

Clear[g, t, a, b, s, trobrid]
trobrid[g_, t_, a_, b_] := DynamicModule[
  {X, Y, Z, tang, norm, binorm, k, l},
  {X[t], Y[t], Z[t]} = g;
  tang = D[g, t]/Simplify[Sqrt[D[g, t].D[g, t]]];
  norm = D[tang, t]/Simplify[Sqrt[D[tang, t].D[tang, t]]];
  binorm = FullSimplify[Cross[tang, norm], t > 0];

  Manipulate[
   Show[
    ParametricPlot3D[g, {t, a, b}],
    Graphics3D[
     {Red, Arrow[{g, tang + g} /. {t -> s}], Blue, 
      Arrow[{g, norm + g} /. {t -> s}], Purple, 
      Arrow[{g, binorm + g} /. {t -> s}]}]
    ],
   {s, a, b}
  ]
 ]

Then:

trobrid[{Cos[t], Sin[t], t/3}, t, 0, 3 Pi]

Mathematica graphics

Issues in your original code:

  1. You should use DynamicModule with Manipulate, rather than Module.
  2. g == {X[t], Y[t], Z[t]}; is incorrect as an assignment; you really want to assign {X[t], Y[t], Z[t]} to the existing value of g, so you want {X[t], Y[t], Z[t]} = g, and you want to use Set (=), not Equal (==).
  3. You need to wrap your graphics objects in Show within Manipulate to combine them and show them superimposed.
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4
  • $\begingroup$ Thank you very much. And what is the command if I want to show for example Torsion and Curvature at each point of the curve. How do I get that into the graphic? $\endgroup$
    – zermelovac
    Mar 20, 2016 at 21:55
  • $\begingroup$ @zermelovac not sure, I haven't really parsed your code for function, just for syntactic correctness. The Frenet-Serret equations may be relevant to you; see previous questions on this site, and the docs for FrenetSerretSystem perhaps? $\endgroup$
    – MarcoB
    Mar 20, 2016 at 22:04
  • $\begingroup$ Let me correct myself. How do I insert text inside a graphic, somewhere in the frame. $\endgroup$
    – zermelovac
    Mar 20, 2016 at 22:07
  • $\begingroup$ @zermelovac Oh! I misunderstood; that's fortunately an easier task :-) Try adding this inside your Graphics3D list of objects within the Manipulate: Inset[Style["s = " <> ToString@Round[s, 0.1], 28, Black], Scaled[{0.3, 0.2, 0}]]. See how it works, then you can use it as a template of sorts to roll your own. $\endgroup$
    – MarcoB
    Mar 20, 2016 at 22:15

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