In computer graphics, a texel, texture element, or texture pixel is the fundamental unit of a

texture map Texture mapping is a method for mapping a texture on a computer-generated graphic. Texture here can be high frequency detail, surface texture, or color. History The original technique was pioneered by Edwin Catmull in 1974. Texture mapping ...

. Textures are represented by

array An array is a systematic arrangement of similar objects, usually in rows and columns. Things called an array include: {{TOC right Music * In twelve-tone and serial composition, the presentation of simultaneous twelve-tone sets such that the ...

s of texels representing the

texture space Texture mapping is a method for mapping a texture on a computer-generated graphic. Texture here can be high frequency detail, surface texture, or color. History The original technique was pioneered by Edwin Catmull in 1974. Texture mappi ...

, just as other

images An image is a visual representation of something. It can be two-dimensional, three-dimensional, or somehow otherwise feed into the visual system to convey information. An image can be an artifact, such as a photograph or other two-dimensiona ...

are represented by arrays of

pixel In digital imaging, a pixel (abbreviated px), pel, or picture element is the smallest addressable element in a raster image, or the smallest point in an all points addressable display device. In most digital display devices, pixels are the smal ...

s. Texels can also be described by image regions that are obtained through simple procedures such as thresholding. Voronoi tesselation can be used to define their spatial relationships—divisions are made at the

midpoint In geometry, the midpoint is the middle point of a line segment. It is equidistant from both endpoints, and it is the centroid both of the segment and of the endpoints. It bisects the segment. Formula The midpoint of a segment in ''n''-dimens ...

s between the

centroid In mathematics and physics, the centroid, also known as geometric center or center of figure, of a plane figure or solid figure is the arithmetic mean position of all the points in the surface of the figure. The same definition extends to any ob ...

s of each texel and the centroids of every surrounding texel for the entire texture. This results in each texel centroid having a

Voronoi polygon In mathematics, a Voronoi diagram is a partition of a plane into regions close to each of a given set of objects. In the simplest case, these objects are just finitely many points in the plane (called seeds, sites, or generators). For each seed t ...

surrounding it, which consists of all points that are closer to its own texel centroid than any other centroid.

Rendering

When texturing a 3D surface or surfaces (a process known as

texture mapping Texture mapping is a method for mapping a texture on a computer-generated graphic. Texture here can be high frequency detail, surface texture, or color. History The original technique was pioneered by Edwin Catmull in 1974. Texture mapping ...

), the renderer maps texels to appropriate pixels in the geometric fragment (typically a triangle) in the output picture. On modern computers, this operation is accomplished on the

graphics processing unit A graphics processing unit (GPU) is a specialized electronic circuit designed to manipulate and alter memory to accelerate the creation of images in a frame buffer intended for output to a display device. GPUs are used in embedded systems, mobi ...

. The texturing process starts with a location in space. The location can be in world space, but typically it is local to a model space so that the texture moves with the model. A projector function is applied to the location to change the location from a three-element vector (

\left (u,v,z \right )

) to a two-element (

\left (x,y\right )

) vector with values ranging from zero to one ( uv).Tomas Akenine-Moller,

Eric Haines Eric Haines is an American software engineer, and is an expert in computer graphics, specifically image rendering. he is with NVIDIA Corporation as Distinguished Engineer. He is a co-author of the book ''Real-Time Rendering'', currently in its ...

, and Naty Hoffman, ''Real-Time Rendering'', Wellesley: A K Peters, 2008. . These values are multiplied by the resolution of the texture to obtain the location of the texel. When a texel is requested that is not on an

integer An integer is the number zero (), a positive natural number (, , , etc.) or a negative integer with a minus sign (−1, −2, −3, etc.). The negative numbers are the additive inverses of the corresponding positive numbers. In the language ...

position,

texture filtering In computer graphics, texture filtering or texture smoothing is the method used to determine the texture color for a texture mapped pixel, using the colors of nearby texels (pixels of the texture). There are two main categories of texture filtering ...

is applied. When a texel is requested that is outside of the texture, one of two techniques is used: clamping or wrapping.

Clamping A wheel clamp, also known as wheel boot, parking boot, or Denver boot, is a device that is designed to prevent motor vehicles from being moved. In its most common form, it consists of a clamp that surrounds a vehicle wheel, designed to preven ...

limits the texel to the texture size, moving it to the nearest edge if it is more than the texture size.

Wrapping Wrapping may refer to: *Buddy wrapping, the act of bandaging a damaged (particularly a fractured) finger or toe together with a healthy one *Overwrap, a wrapping of items in a package of a wrapping over packaging *Wrapping (graphics), the process ...

moves the texel in increments of the texture's size to bring it back into the texture. Wrapping causes a texture to be repeated; clamping causes it to be in one spot only.

References

3D rendering Texture mapping {{compu-graphics-stub

Rendering

See also

References