These variables make it possible to identify groups of geometric entities that share material property expressions and equations. There is a variable for each geometric entity level, and they evaluate to different (but arbitrary) integers on different groups of domains where material property expressions and equations are the same within each group. The solution can therefore normally be assumed to be continuous across domain boundaries where material group variables evaluate to the same value on both sides. This property is used for smoothing plot data across entity boundaries within the group but not across groups with different materials. The option Inside material domains available in the Smoothing list in quality settings for plots uses these variables. See Entering Quality Settings for Plot Settings Windows.

The variable material.entity is available on all entity levels. It is not necessarily integer-valued or even constant on each entity since it is not only affected by material properties and equations on the entity level where it is evaluated, but also by lower levels. For example, material.entity on the domain level is discontinuous at boundaries where there are equation contributions that can potentially make the solution or important postprocessing variables discontinuous.

The applicable variables (except material.entity) are available for postprocessing under Model>Material in the lists of predefined quantities for expressions in plots, for example.