Voxel

From Free net encyclopedia

A voxel (a portmanteau of the words volumetric and pixel) is a volume element, representing a value in three dimensional space. This is analogous to a pixel, which represents 2D image data. Voxels are frequently used in the visualisation and analysis of medical and scientific data. Some true 3D displays use voxels to describe their resolution. For example, a display might be able to show 512×512×512 voxels.

As with pixels, voxels themselves typically do not contain their position in space (their coordinates) - but rather, it is inferred based on their position relative to other voxels (i.e. their position in the data structure that makes up a single volume image).

1 Voxel data
2 Uses
- 2.1 Visualization
- 2.2 Computer gaming
3 Trivia
4 See also
5 External links

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Voxel data

There are two interpretations for a voxel value, depending on usage:

A tiny cube with particular properties in a larger volume.
A point sample in a regularly spaced 3D grid.

The value of a voxel may represent various properties. In CT scans, the values are Hounsfield units, giving the opacity of material to X-rays. Different types of value are acquired from MRI or ultrasound.

Voxels can contain multiple scalar values; in the case of ultrasound scans with B-mode and Doppler data, density, and volumetric flow rate are captured as separate channels of data relating to the same voxel positions.

Other values may be useful for immediate 3D rendering, such as a surface normal vector and color.

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Uses

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Visualization

A volume containing voxels can be visualised either by direct volume rendering or by the extraction of polygon iso-surfaces which follow the contours of given threshold values. The marching cubes algorithm is often used for iso-surface extraction, however other methods exist as well.

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Computer gaming

Many NovaLogic games have used voxel-based rendering technology, including the Delta Force series.

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Trivia

In the minimalist webcomic Pixel, in which pixels inside a computer are the main characters, one 'race' of supporting characters are the voxels, who have the "supernatural" power of moving in three dimensions.

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