tricylinder

Summary

Single function to create a triangulated cylinder. This function mimics Matlab's cylinder behavior, but returns a triangulation object instead of x-, y- and z-coordinates.

Syntax

TR = tricylinder

TR = tricylinder(r)

TR = tricylinder(r,n)

[TR, T, x, y, z] = tricylinder(r,n)

tricylinder(___)

tricylinder(ax,___)

Description

TR = tricylinder returns the triangulation object of a cylinder without drawing it. The cylinder has a radius of 1 and 20 equaly spaced points around its circumference. The bases are parallel to the xy-plane. To draw the cylinder, pass TR to the trisurf or trumesh function.

TR = tricylinder(r) returns the triangulation object of a cylinder with the specified profile curve r, and 20 equally spaced points around its circumference. The function treats each element in r as a radius at equally spaced heights along the unit height of the cylinder.

TR = tricylinder(r,n) returns the triangulation object of a cylinder with the specified profile curve r, and n equally spaced points around its circumference.

[TR, T, x, y, z] = tricylinder(___) returns the triangulation object together with the connectivity matrix T and x-, y-, and z-coordinates.

tricylinder(___) plots the cylinder without returning the coordinates. Use this syntax with any of the input arguments in previous syntaxes.

tricylinder(ax,___) plots into the axes specified by ax instead of the current axes. Specify the axes as the first input argument.

Background

Existing solutions for triangulations are limited to surfaces that can be defined by a function f(x,y)=z and thus not allow cylinders. Solutions based on interpolation have slow performance and do not result in a homogeneous mesh. Just like cylinder, tricylinder allows the simple construction of a cylinder defined by an vector r containing the profile curve and a positive whole number n that defines the number of points around the cylinder circumfence.

Examples

Display Unit Cylinder

Create and plot a cylinder with a radius equal to 1.

tricylinder

Specify Cylinder Radius and Height

Specify the radius of a cylinder by including the input r. Then, specify the height of the cylinder by modifying the z-coordinates of the returned triangulation object.

r = 4;
[~, T, x, y, z] = tricylinder(r);

Specify a height of 20 by modifying the z-coordinates. Plot the cylinder.

h = 20;
z = z*h;
TR = triangulation(T, x, y, z);
trisurf(TR)

Display Multiple Cylinders at Different Locations

Create a cylinder and use the returned coordinates to plot multiple cylinders in different locations.

Create a cylinder defined by the profile function 2 + cos(t).

t = 0:pi/10:2*pi;
r = 2 + cos(t);
[TR, T, x, y, z] = tricylinder(r);

Plot two more cylinders on top of the first cylinder.

hold on
z = z+1;
TR2 = triangulation(T, x, y, z);
z = z+1;
TR3 = triangulation(T, x, y, z);
trisurf(TR2);
trisurf(TR3);