What are Voxels?
A voxel (volumetric pixel) is a unit of volume measurement. The voxel is the three-dimensional counterpart of the two-dimensional pixel (which represents the unit of the area), and therefore the buffer volume (a large 3D voxel array) of voxels can be considered as the three-dimensional counterpart of the two-dimensional pixel buffer. The volumetric graphics is the sector of the computer graphics that employs the buffer volume for the representation of the scenes and concerns the synthesis, manipulation, and rendering of such scenes. Volumetric graphics are the three-dimensional counterpart of raster graphics.
Each voxel possesses numerical values associated with it, which represent some measurable or independent variable properties (for example, color, opacity, density, material, proportion of coverage, index of refraction, velocity, strength, time) of the real phenomenon or object that resides in the volume unit represented by that voxel. The aggregate of voxels, which tessellate the volume buffer, forms the volumetric dataset, which is represented as a discrete regular three-dimensional grid; this is also called volumetric data. Volumetric modeling is the synthesis, analysis, and manipulation of a sampled, calculated and synthetic objects contained within a volumetrics dataset.
Therefore, two interpretations of the term voxel are possible, depending on the use:
- a small cube, with particular properties in a larger space.
- a point (sample) in a 3D grid at regular intervals.
Volumetric display is a visualization method that deals with the representation, manipulation, and rendering of volumetric data. A volume of data represented by the voxels can be displayed directly from the volumetric rendering or through the extraction of a polygonal isosurface, which separates a part of the volume through the identification of a suitable intensity threshold. The marching cubes algorithm is often used for this purpose.
Voxels are used in so-called height maps; these are rectangular matrices that contain height values. Each element of the matrix can be associated with a non-cubic voxel with height equal to the height defined by the matrix and with a fixed size basis and equal for all the locations of the matrix. The height maps contain a single value for each point on the 2D grid, in this way you can represent simple surfaces but not complex surfaces that overlap. Height maps are often used in graphic applications and videogames (even Terasology uses this technique).
Magicavoxel, grid for positioning voxels:
Some examples of voxel models:
