---
name: "v.hull"
section: "1grass"
platform: "linux"
package: "grass-doc"
version: "8.4.1-1"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/v.hull"
---

# v.hull(1grass)

Produces a 2D/3D convex hull for a given vector map.

## NAME

**v.hull**  - Produces a 2D/3D convex hull for a given vector map.

## KEYWORDS

vector, geometry, 3D

## SYNOPSIS

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

### Flags:

- **-r**

  Limit to current region

- **-f**

  Create a ’flat’ 2D hull even if the input is 3D points

- **--overwrite**

  Allow output files to overwrite existing files

- **--help**

  Print usage summary

- **--verbose**

  Verbose module output

- **--quiet**

  Quiet module output

- **--ui**

  Force launching GUI dialog

### Parameters:

- **input**=*name* **\[required\]**

  Name of input vector map\
   Or data source for direct OGR access

- **layer**=*string*

  Layer number or name (’-1’ for all layers)\
   A single vector map can be connected to multiple database tables. This number determines which table to use. When used with direct OGR access this is the layer name.\
   Default: *-1*

- **output**=*name* **\[required\]**

  Name for output vector map

- **cats**=*range*

  Category values\
   Example: 1,3,7-9,13

- **where**=*sql\_query*

  WHERE conditions of SQL statement without ’where’ keyword\
   Example: income \< 1000 and population \>= 10000

## DESCRIPTION

*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.

## EXAMPLE

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.

## SEE ALSO

*v.delaunay*

## AUTHORS

Andrea Aime, Modena, Italy\
 Markus Neteler, ITC-irst (update to 5.7)\
 Benjamin Ducke, CAU Kiel (3D hull support)\
 Martin Landa, CTU in Prague, Czech Republic (vector lines support)

## SOURCE CODE

Available at: v.hull source code (history)

Accessed: Monday Feb 24 17:51:14 2025

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