## TUBEPLOT Creates a Tubeplot

Section: Handle-Based Graphics

### Usage

This `tubeplot` function is from the tubeplot package written by Anders Sandberg. The simplest syntax for the `tubeplot` routine is

        tubeplot(x,y,z)

plots the basic tube with radius 1, where `x,y,z` are vectors that describe the tube. If the radius of the tube is to be varied, use the second form

        tubeplot(x,y,z,r)

which plots the basic tube with variable radius r (either a vector or a scalar value). The third form allows you to specify the coloring using a vector of values:

        tubeplot(x,y,z,r,v)

where the coloring is now dependent on the values in the vector `v`. If you want to create a tube plot with a greater degree of tangential subdivisions (i.e., the tube is more circular, use the form

        tubeplot(x,y,z,r,v,s)

where `s` is the number of tangential subdivisions (default is 6) You can also use `tubeplot` to calculate matrices to feed to `mesh` and `surf`.

        [X,Y,Z]=tubeplot(x,y,z)

returns `N x 3` matrices suitable for mesh or surf. Note that the tube may pinch at points where the normal and binormal misbehaves. It is suitable for general space curves, not ones that contain straight sections. Normally the tube is calculated using the Frenet frame, making the tube minimally twisted except at inflexion points. To deal with this problem there is an alternative frame:

        tubeplot(x,y,z,r,v,s,vec)

calculates the tube by setting the normal to the cross product of the tangent and the vector vec. If it is chosen so that it is always far from the tangent vector the frame will not twist unduly.

### Example

Here is an example of a `tubeplot`.

    --> t=0:(2*pi/100):(2*pi);
    --> x=cos(t*2).*(2+sin(t*3)*.3);
    --> y=sin(t*2).*(2+sin(t*3)*.3);
    --> z=cos(t*3)*.3;
    --> tubeplot(x,y,z,0.14*sin(t*5)+.29,t,10);

Written by Anders Sandberg, asa@nada.kth.se, 2005