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v.hull(1grass) | Grass User's Manual | v.hull(1grass) |
NAME¶
v.hull - Produces a 2D/3D convex hull for a given vector map.KEYWORDS¶
vector, geometry, 3DSYNOPSIS¶
v.hullv.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 inhab >= 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
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.delaunayAUTHOR¶
Andrea Aime, Modena, ItalyMarkus Neteler, ITC-irst (update to 5.7)
Benjamin Ducke, CAU Kiel (3D hull support)
Martin Landa, CTU in Prague, Czech Republic (vector lines support)
Last changed: $Date: 2015-01-15 09:42:19 +0100 (Thu, 15 Jan 2015) $
SOURCE CODE¶
Available at: v.hull source code (history)Main index | Vector index | Topics index | Keywords index | Graphical index | Full index
© 2003-2016 GRASS Development Team, GRASS GIS 7.2.0 Reference Manual
GRASS 7.2.0 |