CreateHullDB()

Summary

Creates an area or a line DBD database based on a TIN.

 

Changes

Added to Version 2016.

 

Syntax

CreateHullDB(tin t, string db_name, array options)

 

Argument	Contents
t	A TIN
db_name	The name of the output geographic file

 

Option	Type	Contents
Generate Lines	Boolean	"True" to generate lines instead of areas; default "False"
Layer Name	String	The name for the new layer
Label	String	The label for the new layer
Omit Inner Faces	Boolean	"True" to omit inner faces of areas (inside of doughnuts); default "False"
Progress Message	String	A progress message
Separate Areas	Boolean	"True" to create separate areas (for those with multiple polygons); default "False"
Radius	Double	The radius of a disc that defines the alpha-point boundary; boundary points are the points where a disc of this radius cannot be "inserted"

 

Notes

• CreateHullDB() generates the alpha-shape described in Edelsbrunner, Herbert; Kirkpatrick, David G.; Seidel, Raimund (1983), "On the shape of a set of points in the plane", IEEE Transactions on Information Theory 29 (4): 551–559.2.

• A very large radius will create a convex hull of all the points. A smaller radius may create disconnected areas. A very small radius will connect none of the points, and thus create an empty area database.

• If radius is not provided, it is assumed to be the maximum double value, resulting in a convex hull.

Example

// Open Elevdata.cdf in the Tutorial folder

SetLayer("Elevation Layer")

point_tin = CreateTriangulation("Elevation Layer|", {{"Field","Elevation"}})

folder = RunMacro("G30 Tutorial Folder")

CreateHullDB(point_tin, folder + "myhull.dbd",

{{"Layer Name","Convex Hull"}}) 

 

Error Codes

Error Type	Meaning
Error	The TIN compound variable is null, or the options are not of the required type

 

See Also

Function	Summary
CreateConvexHullDB()	Creates an area geographic file that encloses all of the points in a TIN
CreateTriangulation()	Creates a Triangulated Irregular Network (TIN)
CreateTriangulationAreaDB()	Creates an area geographic file from the facets in a TIN, with slope and aspect values