Terrain rendering

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[edit] Terrain Rendering

Terrain rendering covers a variety of methods of depicting real world (Earth, Mars, Moon, etc.) or imaginary world surfaces. Most common terrain rendering is depiction of Earth's surface.

It is used in various applications to give an observer a frame of reference. It is also often used in combination with rendering of non-terrain objects, such as trees, buildings, rivers, etc.

There are two major modes of terrain rendering: top down and perspective rendering. Top-down terrain rendering has been known for centuries in the way of cartographic maps. Perspective terrain rendering has also been known for quite some time. However, only with the advent of computers and computer graphics perspective rendering has become mainstream.

Perspective terrain rendering is described in this article.

A typical terrain rendering application consists of a terrain database, a general processing unit, a dedicated graphics processing unit, and a display. A software application is configured to start at initial location in the world space. The output of the application is screen space representation of the real world on a display. Software application uses CPU to identify and load terrain data corresponding to initial location from terrain database, then apply required transformations to build a mesh of points that can be rendered by GPU. GPU completes geometrical transformations, creating screen space objects (such as polygons) that create a picture closely resembling location of the real world.

There is a number of ways to texture surface of terrain. Some applications benefit from using artificial textures, such as elevation coloring, checkerboard or other generic textures. Some applciations attempt to re-create real-world surface to best possible representation using aerial and satellite images.

There is a great variety of methods to generate terrain surfaces. Main problem solved by all these methods is managing number of processed and rendered polygons. It is possible to create a very detailed picture of the world using billions of data points. However such applications are limited to a static pictures. Most uses of terrain rendering are moving images. This requires software application to make decisions on how to simplify (by discarding or approximating) source terrain data. Virtually all terrain rendering applications use Levels of Detail to manage number of data points processed by CPU and GPU.

See main article on LOD, Continuous Levels Of Details ([CLOD]), ROAM, etc.

Terrain rendering is widely used in computer games to represent both Earth's surface and imaginary worlds.

One important application of terrain rendering is in Synthetic Vision systems. Pilots flying aircrafts benefit greatly from ability to see terrain surface at all times regardless of conditions out of the window. See main article on Synthetic vision.