Virtual Attribute Fields
Support for virtual attribute fields, a mature TatukGIS functionality, was significantly extended in the TatukGIS Developer Kernel version 11.33.0. Unlike typical attribute fields, virtual fields (sometimes called built-in fields) exist only in memory with values that update dynamically. Virtual fields offer a convenient way for getting information about individual shapes in vector layers and are commonly used for labelling, section rendering, and creating SQL queries.
Before focusing on the new functionality, let's first review the list of previously supported virtual fields:
provides the shape's UID
True if the shape is selected
True if the shape is hidden
area of a polygon shape expressed in square meters
length of a line shape or the perimeter of a polygon shape expressed in meters
Z coordinate of the first vertex of a 3D shape
M coordinate of the first vertex of a 3D shape
current date and time
Some virtual fields are available also in the TatukGIS Editor product, as built-in attribute table columns in its Data panel.
For more information, visit the documentation at:
The DK 11.33.0 introduced additional virtual fields relating to object geometry:
GIS_MIN_X, GIS_MIN_Y, GIS_MIN_Z, GIS_MIN_M, GIS_MAX_X, GIS_MAX_Y, GIS_MAX_Z, GIS_MAX_M
from coordinates of the vertices defining the shape's extent
GIS_CENTER_X, GIS_CENTER_Y, GIS_CENTER_Z, GIS_CENTER_M
coordinates of the shape’s center (center of the extent)
coordinates of the shape’s centroid
number of points (vertices) composing the shape
number of parts composing the shape
The image below is a graphical representation of virtual fields relating to the geometry of a polygon shape.
Virtual fields relating to polygon shape geometry.