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## Material Interface Reconstruction

Many databases store out their computational meshes with associated materials. The materials are often used to break meshes into subsets that correspond to physical parts of a model. Materials are commonly stored out as a list of materials and material volume fractions for each cell in the database. If a cell has only one material then is a clean cell. If a cell has more than one material, it has some fraction of each of the materials and it is known as a mixed cell. The fraction of the material in a cell if accounted for by the material volume fraction. Since only the volume fractions are known, and not any information about how the materials are distributed in the cell, VisIt must make a guess at the location of the boundaries between materials.

Figure 15

Material interface reconstruction (MIR) is the process of constructing the boundaries between materials, in cells with mixed materials, from the material volume fraction information stored in the database. MIR is not usually needed when you visualize the entire database but when you start to subset the database by removing materials, VisIt must perform MIR to remove only the parts of the database that contain the material to be removed. Without MIR, visualizations containing mixed materials would be very blocky when materials are removed. VisIt's MIR algorithms have several settings, which you can change using the controls in the Material Reconstruction Options Window (see figure), that influence the appearance of the final plot. To open the Material Reconstruction Options Window, click on the Materials option in the Main Window's Controls menu.