# Calculates and plots the convex hull around the plant crown

### Description

This function finds the convex hull (and its surface area and volume) spanning the leaves of the 3D plant, using all coordinates of the leaf edges. The result is smallest set of x, y, z points that defines the convex hull, that is, the polyhedral surface that contains all other points, and is convex.

The implementation is a wrapper for the 'convhulln' function in the from package 'geometry'.

Optionaly, uses the 'rgl' package (see `plot3d`

), to add a plot
of the hull to the current (rgl) device. Opens a new device if none is
currently open. Uses the non-visible function `triangles3d`

to plot the
hull, see details there.

The convex hull is calculated with the qhull algorithm, see
`convhulln`

and references therein.

### Usage

1 |

### Arguments

`xyz` |
An object of class 'plant3d', or a matrix with three columns (xyz coordinates). |

`plotit` |
Logical. If FALSE, returns only volume and surface area. |

`alpha` |
Transparency (0-1). |

### Value

A list with components 'crownvolume' and 'crownsurface', giving the volume and surface of the convex hull.

### Author(s)

Remko Duursma

### References

Duursma, R.A., D.S. Falster, F. Valladares, F.J. Sterck, R.W. Pearcy, C.H. Lusk, K.M. Sendall, M. Nordenstahl, N.C. Houter, B.J. Atwell, N. Kelly, J.W.G. Kelly, M. Liberloo, D.T. Tissue, B.E. Medlyn and D.S. Ellsworth. 2012. Light interception efficiency explained by two simple variables: a test using a diversity of small- to medium-sized woody plants. New Phytologist. 193:397-408.

### Examples

1 2 3 4 5 6 7 8 9 |