Linear Structures in vtdata/vtlib

A Linear Structure is any feature on the earth which can be suitably described by a linear path with a handful of parameters such as height, width, and material.  In the VTP implementation, this includes all kinds of fences, walls, hedges, berms, etc.

The vtdata library stores descriptions in the vtFence class.  vtlib's vtFence3d subclass implements the procedural construction of 3D geometry, using the vtFence properties.  vtStructureArray acts as a container for structure objects, which include vtFence.  See also: vtlib structure classes.

Parametric description

• Location (series of 2D geographic points describing a line)
• PostType (wood, steel, none)
• PostHeight (meters)
• PostSpacing (meters)
• PostWidth (meters)
• PostDepth (meters)
• PostExtension (left, right, double, none)
• ConnectType (wire, chain-link, privet, drystone, none)
• ConnectTop (meters)
• ConnectBottom (meters)
• ConnectWidth (meters)
• ConnectSlope (slope on the sides of the connector)
• ConstantTop (top of connector is constant height (true/false))

All parameters beside Location are optional.
Here is an illustration of the basic geometry:

Future

• With a an extension of simple parameters into a more complex set, or even a degree of scripting embedded into the description, it should be possible to describe large, complex linear structures, such as the Great Wall of China.
• a design goal: the description should be expressible in simple, spoken language.  that way a person could create the database with direct observation and speech recognition.

File IO

• vtStructureArray contains an array of  vtStructure objects and can read and write itself to the VTST file format