Terrain Definition Model Hierarchy

Terrain

Terrain Definition Model : Terrain Definition Model Hierarchy

The Terrain Model World (TRNWLD) element contains the Terrain Definition Model, hence the geometry stored in this element is never considered by clash detection.

All database elements are owned by other elements, therefore elements must be created in a strict order.

TRNWLD elements are administrative and can own a number of Terrain Definition (TRNDEF) and Terrain Surface (TRNSUR) elements. Below the TRNWLD element level the area specific elements are:

TRNDEF

The Terrain Definition (TRNDEF) is a volume defined as a rectangular section from the Terrain, with a thickness added below the lowest point from the surface. More than one definition can be created for a single surface, allowing the Terrain to be split up. The definitions for one surface should not overlap.

Positive and negative primitives can be defined to define changes to the terrain, these are added to the Terrain Definition when modifying it.

Terrain Primitive Holder (TRNPRI), Terrain Restriction Rectangle (TRNRR) and Terrain Solid Primitive Holder (TRNSLD) elements are owned by TRNDEF elements.

TRNDEF elements are linked to TRNSUR elements are linked by a property called SurLnk which is the reference to terrain surface. TRNDEF elements are also linked to TRNMOD elements by a property called DeflLnk which is the link to terrain definition.

TRNPRI

TRNPRI elements are owned by TRNDEF elements, these elements are container elements for primitives elements.

The TRNPRI elements has a property called the Terrain Definition Volume or Tvol. The volume is calculated by the solid described as the terrain surface with the bottom plane defined by the Bothei attribute and with the TRNRR element applied. The volume is calculated when the command GENTRM is used.

TRNRR

TRNRR elements are owned by TRBDEF elements, the rectangle is used to restrict the Terrain Definition Model.

TRNSLD

TRNSLD elements are owned by TRNDEF elements, the element contains the volumetric representation of the Terrain Definition Model.

TRNSUR

A terrain surface is imported and created by the IMP command. This is the same command that is used by the Mechanical Equipment Interface (MEI).