Terrain rendering
Encyclopedia
Terrain rendering covers a variety of methods of depicting real-world or imaginary world surface
s. Most common terrain
rendering
is the 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 tree
s, building
s, river
s, 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 central processing unit
(CPU), a dedicated graphics processing unit
(GPU), 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. The software application uses the CPU to identify and load terrain data corresponding to initial location from the terrain database, then applies the required transformations to build a mesh
of points that can be rendered by the GPU, which completes geometrical transformations, creating screen space objects (such as polygon
s) that create a picture closely resembling the location of the real world.
the terrain surface. Some applications benefit from using artificial textures, such as elevation coloring, checkerboard
, or other generic textures. Some applications attempt to recreate the real-world surface to the best possible representation using aerial photography
and satellite imagery
.
In video games, texture splatting
is used to texture the terrain surface.
to manage number of data points processed by CPU and GPU. There are several modern algorithms for terrain surfaces generating.
One important application of terrain rendering is in synthetic vision
systems. Pilots flying aircraft benefit greatly from the ability to see terrain surface at all times regardless of conditions outside the aircraft.
Surface
In mathematics, specifically in topology, a surface is a two-dimensional topological manifold. The most familiar examples are those that arise as the boundaries of solid objects in ordinary three-dimensional Euclidean space R3 — for example, the surface of a ball...
s. Most common terrain
Terrain
Terrain, or land relief, is the vertical and horizontal dimension of land surface. When relief is described underwater, the term bathymetry is used...
rendering
Artistic rendering
Rendering in visual art and technical drawing means the process of creating, shading, and texturing of an image, especially a photorealistic one. It can also be used to describe the quality of execution of that process...
is the depiction of Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
's surface.
It is used in various applications to give an observer a frame of reference
Frame of reference
A frame of reference in physics, may refer to a coordinate system or set of axes within which to measure the position, orientation, and other properties of objects in it, or it may refer to an observational reference frame tied to the state of motion of an observer.It may also refer to both an...
. It is also often used in combination with rendering of non-terrain objects, such as tree
Tree
A tree is a perennial woody plant. It is most often defined as a woody plant that has many secondary branches supported clear of the ground on a single main stem or trunk with clear apical dominance. A minimum height specification at maturity is cited by some authors, varying from 3 m to...
s, building
Building
In architecture, construction, engineering, real estate development and technology the word building may refer to one of the following:...
s, river
River
A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...
s, etc.
There are two major modes of terrain rendering: top-down and perspective
Perspective (geometry)
In geometry, two triangles are perspective if, when the sides of each triangle are extended, they meet at three collinear points. The line which goes through the three points is known as the perspectrix, perspective axis, homology axis, or axis of perspectivity. The triangles are said to be...
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
Computer graphics
Computer graphics are graphics created using computers and, more generally, the representation and manipulation of image data by a computer with help from specialized software and hardware....
perspective rendering has become mainstream.
Perspective terrain rendering is described in this article.
Structure
A typical terrain rendering application consists of a terrain databaseDatabase
A database is an organized collection of data for one or more purposes, usually in digital form. The data are typically organized to model relevant aspects of reality , in a way that supports processes requiring this information...
, a central processing unit
Central processing unit
The central processing unit is the portion of a computer system that carries out the instructions of a computer program, to perform the basic arithmetical, logical, and input/output operations of the system. The CPU plays a role somewhat analogous to the brain in the computer. The term has been in...
(CPU), a dedicated graphics processing unit
Graphics processing unit
A graphics processing unit or GPU is a specialized circuit designed to rapidly manipulate and alter memory in such a way so as to accelerate the building of images in a frame buffer intended for output to a display...
(GPU), 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. The software application uses the CPU to identify and load terrain data corresponding to initial location from the terrain database, then applies the required transformations to build a mesh
Polygon mesh
A polygon mesh or unstructured grid is a collection of vertices, edges and faces that defines the shape of a polyhedral object in 3D computer graphics and solid modeling...
of points that can be rendered by the GPU, which completes geometrical transformations, creating screen space objects (such as polygon
Polygon
In geometry a polygon is a flat shape consisting of straight lines that are joined to form a closed chain orcircuit.A polygon is traditionally a plane figure that is bounded by a closed path, composed of a finite sequence of straight line segments...
s) that create a picture closely resembling the location of the real world.
Texture
There are a number of ways to textureTexture mapping
Texture mapping is a method for adding detail, surface texture , or color to a computer-generated graphic or 3D model. Its application to 3D graphics was pioneered by Dr Edwin Catmull in his Ph.D. thesis of 1974.-Texture mapping:...
the terrain surface. Some applications benefit from using artificial textures, such as elevation coloring, checkerboard
Checkerboard
A checkerboard or chequerboard is a board of chequered pattern on which English draughts is played. It is an 8×8 board and the 64 squares are of alternating dark and light color, often red and black....
, or other generic textures. Some applications attempt to recreate the real-world surface to the best possible representation using aerial photography
Aerial photography
Aerial photography is the taking of photographs of the ground from an elevated position. The term usually refers to images in which the camera is not supported by a ground-based structure. Cameras may be hand held or mounted, and photographs may be taken by a photographer, triggered remotely or...
and satellite imagery
Satellite imagery
Satellite imagery consists of photographs of Earth or other planets made by means of artificial satellites.- History :The first images from space were taken on sub-orbital flights. The U.S-launched V-2 flight on October 24, 1946 took one image every 1.5 seconds...
.
In video games, texture splatting
Texture Splatting
In computer graphics, texture splatting is a method for combining different textures. The method works by applying an alphamap to the higher levels, revealing the layers underneath where the alphamap is partially or completely transparent...
is used to texture the terrain surface.
Generation
There are a great variety of methods to generate terrain surfaces. The 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 static pictures. Most uses of terrain rendering are moving images, which require the software application to make decisions on how to simplify (by discarding or approximating) source terrain data. Virtually all terrain rendering applications use level of detailLevel of detail
In computer graphics, accounting for level of detail involves decreasing the complexity of a 3D object representation as it moves away from the viewer or according other metrics such as object importance, eye-space speed or position....
to manage number of data points processed by CPU and GPU. There are several modern algorithms for terrain surfaces generating.
Applications
Terrain rendering is widely used in computer games to represent both Earth's surface and imaginary worlds. Some games also have terrain deformation (or deformable terrain).One important application of terrain rendering is in synthetic vision
Synthetic vision
A Synthetic Vision System is a computer-mediated reality system for aerial vehicles, that uses 3D to provide pilots with clear and intuitive means of understanding their flying environment....
systems. Pilots flying aircraft benefit greatly from the ability to see terrain surface at all times regardless of conditions outside the aircraft.
See also
- ROAMROAMReal-time optimally adapting mesh , is a continuous level of detail algorithm that optimizes terrain meshes. On modern computers, sometimes it is more effective to send a small amount of unneeded polygons to the GPU, rather than burden the CPU with LOD calculations—making algorithms like...
- GeomipmappingGeomipmappingGeomipmapping or geometrical mipmapping is a real-time block-based terrain rendering algorithm developed by W.H. de Boer in 2000 that aims to reduce CPU processing time which is a common bottleneck in level of detail approaches to terrain rendering...
- Geometry ClipmapsClipmapClipmapping is a method of clipping a mipmap to a subset of data pertinent to the geometry being displayed. This is useful for loading as little data as possible when memory is limited, such as on a graphics processing unit.- External links :* * *...
- Virtual Terrain Project