Isosurface
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![Zirconocene with an isosurface showing areas of the molecule susceptible to electrophilic attack. Image courtesy of Accelrys (http://www.accelrys.com)](../../../upload/thumb/c/c2/Isosurface_on_molecule.jpg/180px-Isosurface_on_molecule.jpg)
An isosurface is a three-dimensional analog of an isocontour. It is a surface that represents points of a constant value (e.g. pressure, temperature, velocity, density) within a volume of space; in other words, it is a level set of a continuous function whose domain is 3-space.
Isosurfaces are normally displayed using computer graphics, and are used as data visualization methods in computational fluid dynamics (CFD), allowing engineers to study features of a fluid flow (gas or liquid) around objects, such as aircraft wings. An isosurface may represent an individual shockwave in supersonic flight, or several isosurfaces may be generated showing a sequence of pressure values in the air flowing around a wing. Isosurfaces tend to be a popular form of visualization for volume datasets since they can be rendered by a simple polygonal model, which can be drawn on the screen very quickly.
In medical imaging, isosurfaces may be used to represent regions of a particular density in a three-dimensional CT scan, allowing the visualization of internal organs, bones, or other structures.
Numerous other disciplines that are interested in three-dimensional data often use isosurfaces to obtain information about pharmacology, chemistry, geophysics and meteorology.
A popular method of constructing an isosurface from a data volume is the marching cubes algorithm.