NAME

v.extrude - Extrudes flat vector features to 3D vector features with defined height.
Optionally the height can be derived from sampling of elevation raster map.

KEYWORDS

vector, geometry, sampling, 3D

SYNOPSIS

v.extrude
v.extrude --help
v.extrude [-t] input=name [layer=string] [cats=range] [where=sql_query] [type=string[,string,...]] output=name [zshift=float] [height=float] [height_column=name] [elevation=name] [method=string] [scale=float] [null_value=float] [--overwrite] [--help] [--verbose] [--quiet] [--ui]

Flags:

-t: Trace elevation
--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
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
type=string[,string,...]: Input feature type
Options: point, line, area
Default: point,line,area
output=name [required]: Name for output vector map
zshift=float: Shifting value for z coordinates
Default: 0
height=float: Fixed height for 3D vector features
height_column=name: Name of attribute column with feature height
elevation=name: Elevation raster map for height extraction
method=string: Sampling interpolation method
Options: nearest, bilinear, bicubic
Default: nearest
nearest: Nearest-neighbor interpolation
bilinear: Bilinear interpolation
bicubic: Bicubic interpolation
scale=float: Scale factor sampled raster values
Default: 1.0
null_value=float: Height for sampled raster NULL values

DESCRIPTION

v.extrude creates faces, kernels or 3D lines based on input 2D vector features. Points are converted to 3D vertical lines, lines to faces and areas to volumes (composition of closed set of faces and kernel).

If elevation parameter is used then 3D vector features follow the elevation model by using individual elevation values for the vertices. Height for vertices is interpolated from elevation raster map using given interpolation method.

NOTES

v.extrude extrudes vector features which means that points are converted to vertical lines. Lines and area boundaries are extruded to a set of faces, each segment defines one face. Area centroids are written as kernels. Area as a composition of boundaries and centroid is stored as a closed set of faces and kernel which define a volume.

For conversion of 2D points or lines to 3D can be used v.to.3d or v.drape. In opposite to v.extrude, these modules do not extrude vector features, they defines z-coordinate for the features from given parameters or by sampling elevation raster map values. It means that no feature type conversion is applied, points remain still points in the output vector map. Same applies for the lines.

v.extrude modifies only features geometry. Feature categories remain untouched and attribute data is copied from input vector map to the output.

By default, all features (including features without category) from input vector map are processed (layer=-1). Feature selection can be applied by layer, cats or where parameter.

EXAMPLES

3D houses with fixed height


v.extrude input=houses output=houses3D height=5 type=area

3D houses with individual height


v.extrude input=houses output=houses3D elevation=dem height_column=height type=area

Convert 2D points to 3D vertical lines with fixed height


v.extrude input=geodetic_pts output=points3D height=200 type=point

AUTHORS

Jachym Cepicky,
Updated for GRASS 7 by Martin Landa, FBK-irst, Italy and Czech Technical University in Prague, Czech Republic

SOURCE CODE

Available at: v.extrude source code (history)