User's Guide

Virtualwind   →   Virtualwind Entities   →   Domain

Domain

The Domain entity represents a rectangular volume in 3D space on which the simulation is carried out. It has three parts: Extents, Extents Coordinate System, and World Coordinate System. Their respective Model items are shown below.


To create a Domain, access the Entities  →  Domain  →  Create Domain sub-menu item from the Virtualwind main menu. A Domain item, as shown above, will then appear in the Entities & Monitors tree. Once created, it cannot be deleted, but you can modify its settings as explained below.

Extents

Extents define the size (in meters) of the Domain by specifying its upwind X coordinate, downwind X coordinate, width, and height. The upwind and downwind X coordinates are with respect to the extents coordinate system. If you think of the extents as an iso-oriented box whose edges are parallel to the X, Y, and Z axes of the extents coordinate system, the upwind X coordinate defines the position of its in-flow plane and the downwind X coordinate defines the position of its out-flow plane. The width defines its two side planes which have the same distance to the origin of the extents coordinate system. The height defines its bottom plane (representing the ground whose Z coordinate is always zero in the extents coordinate system) and top plane.

Note that Virtualwind limits the height of extents to be no greater than 600m. If you specify a greater value, it will be truncated to 600m automatically.

In the viewport, the extents are represented by the outline of the box and its bottom plane. You can change their appearance in the viewport by manipulating the settings under the Actor item of extents.

Extents Coordinate System

The extents coordinate system defines the relative position and orientation of extents with respective to the world coordinate system. Shown as the red coordinate system in the figure below, the extents coordinate system is always defined in such a way that the wind blows along its positive X direction, the ground is at Z=0, and the positive Z direction is pointing to the sky. Therefore, if you change the wind direction, you essentially change the extents coordinate system so that its X axis aligns with the wind direction and the extents's orientation will change as well.


World Coordinate System

The world coordinate system is the coordinate system within which the geometric models of your Buildings, Canopies, Terrain, Smokebombs, and Tracer Particle Generators are defined. Typically, there is no reason for you to change its settings. In the above figure, it is shown in blue.

In the viewport, both the extents and the world coordinate systems are represented by their origins and their three positive axes. You can change their appearance by manipulating the settings of their Actor items.