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 |