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4 Interpretation and Presentation of Results     continued...

Visualization tools are available for displaying two dimensional field data of the form as traditional contour maps, color coded raster maps, and as a three dimensional surface, . Traditional graphics tools have allowed for this type of data presentation for a long time. Modern visualization tools add some new capabilities for this type of data display. Computer rendering techniques that are used to prepare photo-realistic images of scene descriptions are now in wide use for architecture and engineering. Textures can be applied to the surface renderings to enhance the perception of the three dimensional nature of the surface. Tools are now available to allow the overlay of the color contour data described above onto a surface plot of a second parameter, allowing the simultaneous display of two spatial variables and two field values.

Three dimensional field data of the form can be rendered in a variety of ways. Typically, the entire field of spatial values and the function value at each node can be assimilated by the software tool and a variety of output forms can be chosen interactively by the user. Examples of the output choices are color raster maps of one or many slices along a plane through the 3-D field, three dimensional dices where color contours are rendered on each surface of the subregion, and isosurface renderings where the surface formed by a particular isovalue is displayed. The isosurface displays are again enhanced by ray-tracing and other techniques to make the three dimensional shape clear to the observer. Even more sophisticated renderings of isosurfaces allow multiple isovalues to be displayed by controlling the apparent translucency of the outer isosurfaces.