In
computer graphics, a texel, texture element, or texture pixel is the fundamental unit of a
texture map. Textures are represented by
array
An array is a systematic arrangement of similar objects, usually in rows and columns.
Things called an array include:
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Music
* In twelve-tone and serial composition, the presentation of simultaneous twelve-tone sets such that the ...
s of texels representing the
texture space, 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-dimension ...
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 s ...
s.
Texels can also be described by
image regions that are obtained through simple procedures such as
thresholding.
Voronoi tesselation
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 th ...
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 ...
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 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 mappi ...
), 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, mo ...
.
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 (
) to a two-element (
) vector with values ranging from zero to one (
uv).
[Tomas Akenine-Moller, Eric Haines, 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 is applied.
When a texel is requested that is outside of the texture, one of two techniques is used: clamping or wrapping.
Clamping limits the texel to the texture size, moving it to the nearest edge if it is more than the texture size.
Wrapping 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.
See also
*
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 s ...
*
Resel
*
Voxel
In 3D computer graphics, a voxel represents a value on a regular grid in three-dimensional space. As with pixels in a 2D bitmap, voxels themselves do not typically have their position (i.e. coordinates) explicitly encoded with their values. ...
References
3D rendering
Texture mapping
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