voxel represents a value in a regular grid in three-dimensional space. As with pixels in bitmaps, voxels themselves usually have no position (coordinates) explicitly encoded along with their values. In contrast, the rendering system concludes the position of voxel based on its position relative to other voxels (ie, its position in the data structure forming a volumetric image). Unlike pixels and voxels, dots and polygons are often explicitly represented by their vertex coordinates. The immediate consequence of this difference is that polygons can efficiently represent simple 3D structures with lots of vacant or homogeneously filled space, while voxels excel in representing a homogeneously unfilled sample space.
Voxel is often used in visualization and analysis of medical and scientific data (eg GIS). Some volumetric displays use voxels to illustrate the resolution. For example, the screen may display 512ÃÆ' â € "512ÃÆ'â €" 512 voxels.
The voxel is analogous to the word "pixel", with vo representing "volume" and el representing "element"; the formation is similar to el for "element" including the words "pixel" and "texel".
Video Voxel
Rendering
Volumes described as voxels can be visualized either by direct volume rendering or by the extraction of the iso-surface polygons following the contour of the given threshold value. Marching cubes algorithms are often used for isosurface extraction, but other methods also exist.
Both ray-tracing and ray-casting, as well as rasterisation, can be applied to voxel data to get 2D raster graphics to illustrate on the monitor.
Rasterize additional errors
Another technique for voxels involves a raster graph in which a person simply rayraces each pixel from the screen into a scene, tracing an error term to determine when to step. A typical implementation will give a ray to every display pixel that starts at the bottom of the screen using what's known as y-buffer. When a voxel is reached that has a higher y value in the view it is added to the previous value y-override buffer and connects to the previous y-value on the color value interpolation screen. There is a big disadvantage to voxel rasterization when transformation is applied which causes severe aliasing. The advantage is the ability to rasterise using cheap integers calculations on CPUs without hardware acceleration.
Issued, and other 1990s video games use this graphics technique for effects such as reflection and lump-mapping and usually for field rendering. The Cursed Graphics Machine is primarily a combination of a high-rise casting machine, used to create landscapes, and a texture mapping polygon machine used to create objects. The "Machine Programming" section of the game credits in the manual has several sub-sections related to the graph, including: "Landscape Machine", "Polygon Machine", "Water & Shadow Machine" and "Special Effects Engine". Although Outcast is often cited as a voxel technology pioneer, this is somewhat misleading. This game does not actually model the voxel three-dimensional volume. Instead, it modeled the soil as a surface, which can be seen as composed of voxels. The soil is decorated with objects that are modeled using polygons that are mapped textures. When Outcast is developed, the term "voxel machine", when applied to computer games, is usually called a casting machine (eg VoxelSpace engine). On the machine technology page of the gaming website, landscape engines are also referred to as "Voxels machines". This machine is purely software based; it does not depend on hardware acceleration through 3D graphics card.
John Carmack also experimented with Voxels for the Quake III engine. One of the problems cited by Carmack is the lack of a graphics card designed specifically for rendering as it requires them to be a given software.
Comanche is also the first commercial flight simulation based on voxel technology. NovaLogic uses an exclusive Voxel Space engine developed for the company by Kyle Freeman (entirely written in Assembly language) to create an open landscape. This rendering technique allows a more detailed and realistic field compared to simulations based on vector graphics at that time.
Gallery
Maps Voxel
Voxel Data
Voxel represents a single sample, or data point, on a regularly spaced three-dimensional grid. This data point can consist of a single piece of data, such as opacity, or multiple pieces of data, such as colors other than opacity. Voxel represents only one point on this grid, not volume; the space between each voxel is not represented in the voxel-based dataset. Depending on the type of data and the intended use of the dataset, this lost information may be reconstructed and/or approached, eg through interpolation.
Voxel values ​​can represent various properties. In CT scan, the value is the Hounsfield unit, giving the opacity of the material to X-rays. Different types of values ​​are obtained from MRI or ultrasound.
Voxel can contain multiple scalar values, essentially vector data (tensor); in the case of ultrasound scans with B-mode and Doppler data, the density, and the volumetric flow rate are captured as separate channels of data relating to the same voxel position.
While voxels provide the benefits of precision and depth of reality, they are usually large and heavy data sets to manage given the general computer bandwidth. However, through efficient compression and manipulation of large data files, interactive visualization can be enabled on consumer market computers.
Other values ​​may be useful for direct 3D rendering, such as normal surface vectors and colors.
Usage
Although scientific volume visualization does not require actual modification of voxel data, voxel editors can be used to create artwork (especially 3D pixel art) and models for voxel-based games. Some editors focus on a single approach to edit voxel while others mix different approaches. Some common approaches are:
- Slice based: The volume is sliced ​​in one or more axes and users can edit each image individually using the 2D raster editor tool. It usually stores color information in voxels.
- Sculpture: Similar to the vector counterpart but without any topological constraints. It usually stores density information in voxels and lack of color information.
- Building blocks: Users can add and remove blocks like toy sets of constructs.
Voxel editor for game
Many game developers use internal editors that are not released to the public, but some games have publicly available editors, some of which are created by players.
- Slice-based Voxel Section Editor III for Command & amp; Conquer: Tiberian Sun and Command & amp; Conquer: Red Alert 2 .
- SLAB6 and VoxEd are sculptural voxel editors used by the Voxlap game engine, including Voxelstein 3D and Ace of Spades .
- The official Sandbox 2 editor for the game CryEngine 2 (including Crysis ) has support for sculpting voxel-based terrain.
- The C4 engine and editor support multiple multiple layer levels (LOD) voxel by applying the patent-free Transvoxel algorithm.
- Qubicle is a simple professional voxel editor. It has export support to Unity game engines, as well as many of the more common 3d modeling formats.
- The Atomontage Engine [1] is a professional voxel engine also including a physics engine.
General-purpose voxel editor
There are several voxel editors available that are not tied to a particular game or machine. They can be used as an alternative or complement to traditional 3D vector modeling.
Extensions
The voxel generalization is doxel , or dynamic voxel. This is used in the case of 4D datasets, for example, a sequence of images representing 3D space along with other dimensions such as time. In this way, an image can contain 100ÃÆ' â € "100ÃÆ'â €" 100ÃÆ' â € "100 doxels, which can be seen as a series of 100 frames of 100ÃÆ'â €" 100ÃÆ'â € "100 images (the equivalent for 3D images will show a cross section transverse 2D) from the image in each frame). Although the storage and manipulation of such data requires a large amount of memory, it allows the representation and analysis of the spacetime system.
See also
- Pixels - image elements
- Resel - the resolution element
- Oreo voxel is rare
- Texel - texture element
- Maxel - the material element
- Tixel - tactile element
- Rendering volume
- Volume nets
- Tomography
References
External links
- Games with voxel graphics on MobyGames
- The basics of voxelization
Source of the article : Wikipedia
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