v.hull(1grass)

Usage

v.hull

v.hull --help

v.hull [-rf] input=name [layer=string] output=name [cats=range] [where=sql_query] [--overwrite] [--help] [--verbose] [--quiet] [--ui]

Keywords

vector, geometry, 3D

Overview

v.hull computes the convex hull of a vector map and outputs the convex hull polygon as a vector area map. The convex hull, or convex envelope, for an object or a set of objects is the minimal convex set containing the given objects. This module creates a vector polygon containing all vector points or lines of the input map.

In the case of 3D input points, the hull will be a 3D hull as well, unless the user specifies the -f flag. The 3D hull will be composed of triangular faces.
Fig: Convex hull polygon created with v.hull

Notes

In order to use the where option the layer option must be set to a positive number (the default is ’-1’ for ’all layers’), otherwise all points from all layers will be used and the cats and where options will be ignored.

Examples

Example of v.hull 3D output (using two random 3D point clouds, North Carolina sample data set):

g.region rural_1m -p
r.mapcalc "zero = 0"
v.random -z output=random3d_a n=10 zmin=0 zmax=200
v.random -z output=random3d_b n=15 zmin=400 zmax=600
v.hull input=random3d_a output=random3d_a_hull
v.hull input=random3d_b output=random3d_b_hull
d.mon wx0
d.vect random3d_a_hull
d.vect random3d_a color=red
d.vect random3d_b_hull
d.vect random3d_b color=red
# 3D view in wxGUI (g.gui)

Fig: Convex hull in 3D from 3D points created with v.hull

References

•: M. de Berg, M. van Kreveld, M. Overmars, O. Schwarzkopf, (2000). Computational geometry, chapter 1.1, 2-8.

•: J. O’Rourke, (1998). Computational Geometry in C (Second Edition), chapter 4.

Source code

Available at: v.hull source code (history)

Accessed: Monday Feb 24 17:51:14 2025

Releases

10 releases since Debian 4.0 (Etch); the text changed 9 times.

4.0
5.0
6.0
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