Use the Iso tool to display single iso values (iso surfaced for solids or iso line for shells) dependent on results data.

The result data used to calculate the iso surfaces or values can be specified independently of the result data selected in the Contour panel, even though most of result selection options are similar to the contour options. Since an iso value is independent of contour results, for OptiStruct design space optimization results, you can apply a single iso surface for density, then contour stress results on the generated iso surface. Combining contour, iso value, and transparent global boundary geometry (shortcut key "T") is an excellent way to investigate hot spots of result data. By varying the iso value slider bar, you can easily observe critical areas.
From the Results toolbar, click Iso .
Note: You can also select Plot > Iso from the Results menu.

Figure 1. Iso Panel