Outcast, and other 1990s video games employed this graphics technique for effects such as reflection and bump-mapping and usually for terrain rendering. The advantage was the ability to rasterise using cheap integer calculations on a CPU without hardware acceleration. There is a major downside to voxel rasterization when transformation is applied which causes severe aliasing. When a voxel is reached that has a higher y value on the display it is added to the y-buffer overriding the previous value and connected with the previous y-value on the screen interpolating the color values. A typical implementation will raytrace each pixel of the display starting at the bottom of the screen using what is known as a y-buffer. Incremental error rasterisation Īnother technique for voxels involves raster graphics where one simply raytraces every pixel of the display into the scene, tracking an error term to determine when to step. The marching cubes algorithm is often used for isosurface extraction, however other methods exist as well.īoth ray-tracing and ray-casting, as well as rasterisation, can be applied to voxel data to obtain 2D raster graphics to depict on a monitor. Ī volume described as voxels can be visualized either by direct volume rendering or by the extraction of polygon iso-surfaces that follow the contours of given threshold values. The word voxel originated by analogy with the word 'pixel', with vo representing 'volume' and el representing 'element' similar formations with el for 'element' include the words 'pixel' and 'texel'. For example, a display might be able to show 512×512×512 voxels. Some volumetric displays use voxels to describe their resolution. Voxels are frequently used in the visualization and analysis of medical and scientific data (eg. A direct consequence of this difference is that polygons can efficiently represent simple 3D structures with lots of empty or homogeneously filled space, while voxels excel at representing regularly sampled spaces that are non-homogeneously filled. In contrast to pixels and voxels, points and polygons are often explicitly represented by the coordinates of their vertices. Instead, rendering systems infer the position of a voxel based upon its position relative to other voxels (i.e., its position in the data structure that makes up a single volumetric image). As with pixels in a bitmap, voxels themselves do not typically have their position (their coordinates) explicitly encoded along with their values. A voxel represents a value on a regular grid in three-dimensional space.

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