When running a dynamic analysis in RISA-3D using response spectra, each mode shape and participation is found according to the mass/mass distribution and stiffness of your structure.
These different mode shapes are combined for analysis. However, this combining of mode shapes produces an overall deflected shape that is hard to discern what the different mode shapes look like.
This is why RISA-3D provides an option to view the deflected shape for the combined spectral response (via the Load Combinations spreadsheet) as well as each individual mode shape.
To view the individual mode shapes of a solved model, open the Plot Options dialog and go to the Deflection Diagrams tab. There we have an option to animate a single mode shape or ALL mode shapes.
This provides you with the ability to compare each mode shape graphically to understand how the combined deflected shape was reached.