Spherical texture mapping

Texture mapping is a method, pioneered by Edwin Catmull, of adding detail, surface texture, or colour to a computer-generated graphic or 3D model. A texture map is applied (mapped) to the surface of a shape. This process is akin to applying gift wrapping paper to a plain white box. In the example at right, a texture map of the Earth's coloration is applied to a sphere to create the illusion of color detail that would take very many additional polygons to realise otherwise. This kind of coloration is the most common application of texture mapping. A graphic representing spherical texture mapping. ... A graphic representing spherical texture mapping. ... Edwin Catmull after receiving a medal at SIGGRAPH 2001. ... ... Computer-generated imagery (CGI) is the application of the field of computer graphics (or more specifically, 3D computer graphics) to special effects. ... This article does not cite its references or sources. ...

Multitexturing is the use of more than one texture at a time on a polygon^[1]. This has various uses, sometimes as a way of applying a light map to a surface, which is faster than requiring the graphics hardware to do lighting calculation for that surface on the fly, or more recently bump mapping has become popular, which allows a texture to directly control the lighting calculations. By adjusting the reflections, the bump mapping can give the appearance of different surfaces, such as tree bark or rough concrete, in addition to the usual detailed coloring. A Lightmap is a data structure which contains the brightness of surfaces in a game. ... A sphere without bump mapping. ...

The way the resulting pixels on the screen are calculated from the texels (texture pixels) is governed by texture filtering. The fastest method is to use the nearest neighbour interpolation, but bilinear interpolation is commonly chosen as good tradeoff between speed and accuracy. In the event of a texture cooridinate being outside the texture, it is either clamped or wrapped. This example shows an image with a portion greatly enlarged, in which the individual pixels are rendered as little squares and can easily be seen. ... ... In computer graphics, texture filtering is the method used to determine the texture color for a texture mapped pixel, using the colors of nearby texels (pixels of the texture). ... The introduction to this article provides insufficient context for those unfamiliar with the subject matter. ... In mathematics, bilinear interpolation is an extension of linear interpolation for interpolating functions of two variables. ... In computer graphics, clamping is the process of limiting a position to an area. ... In computer graphics, wrapping is the process of limiting a position to an area. ...

At the hardware level usually texture coordinates are specified at each vertex of a given triangle (any polygon may be broken down into triangles for rendering), and these coordinates are interpolated as part of a calculation that is an extension of Bresenham's line algorithm. Direct interpolation of the texture coordinates between vertices results in affine texture mapping, which causes a perceivable discontinuity between adjacent triangles when the 3D geometry of the specified triangle is at an angle to the plane of the screen, perspective correction is more realistic, and adjusts the texture coordinate interpolation as a function of the 3D depth of each pixel. Because perspective correction involves slightly more calculation it can negatively affect performance^[2], though most modern graphics hardware implements perspective correct texturing. Bresenhams line algorithm is an algorithm that determines which points in an n-dimensional raster should be plotted in order to form a close approximation to a straight line between two given points. ...

See also

• Bump mapping
• Clamping
• Normal mapping
• Displacement mapping
• Edwin Catmull
• Texture filtering
• Texture splatting - a technique for combining textures.
• Wrapping (graphics)

A sphere without bump mapping. ... In computer graphics, clamping is the process of limiting a position to an area. ... Normal Mapping used to re-detail simplified meshes. ... It has been suggested that this article or section be merged with Displacement map. ... Edwin Catmull after receiving a medal at SIGGRAPH 2001. ... In computer graphics, texture filtering is the method used to determine the texture color for a texture mapped pixel, using the colors of nearby texels (pixels of the texture). ... In computer graphics, Texture splatting is a method for combining different textures. ... In computer graphics, wrapping is the process of limiting a position to an area. ...

References

1. ^ : Multitexture)
2. ^ : pg. 1285)

External links

• Graphics for the Masses by Paul Rademacher
• Introduction into texture mapping using C and SDL
• Programming a textured terrain using XNA/DirectX, from www.riemers.net