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## Finding materials with low volume fractions

Figure 18

When mixed cells contain several materials, the Zoo-based MIR algorithm will often omit materials with very small volume fractions, leaving only the materials in the mixed cell that had the highest volume fractions. If you want to plot materials in mixed cells where the volume fraction is very small then you can try using the Isovolume MIR algorithm since it can be used to find materials whose volume fractions are above a user-specified threshold. figure shows an example of a dataset containing five mixed materials where the first four mixed materials are roughly equal in the amount of area that they occupy. The fifth material has a volume fraction that never exceeds 0.08 so it is omitted by the Zoo-based MIR algorithm due to its comparatively low volume fraction. To ensure that VisIt plots the fifth material, the Isosurface MIR algorithm is used with a Volume Fraction for Isovolume setting of 0.02. Using the Isovolume MIR algorithm with a low Volume Fraction for Isovolume value can find materials that have been distributed into many heavily mixed cells.