As soon as you've set up a MassFX simulation, you can test the settings by playing it in the viewports. If problems occur, it might be obvious what's going wrong, but if not you can use the MassFX Visualizer to analyze the simulation in detail.
Running the Simulation
To start the simulation, click the 
Start Simulation button on the MassFX toolbar. As the simulation runs, it updates in all visible viewports, showing you the results of the simulation as it progresses.
When the simulation starts, display of physical shapes is disabled. If you want to see these (and more) during simulation, use the MassFX Visualizer.
Enabling the MassFX Visualizer
The MassFXVisualizer provides real-time visual information about the simulation, as it runs, in the viewports. To enable it:
- Open the MassFX Tools dialog to the Display panel.
- On the MassFX Visualizer rollout, turn on Enable Visualizer and turn on the properties to display during the simulation.
The properties include Collision Meshes, which display physical shapes for every rigid body in the simulation. The Collision Meshes option is on by default.