Use the Home tab > Simulation > Sim Mode menu to select the simulation type:
Centerline — Simulates the centerline of the toolpath in the graphics window using the current view. If Keep toolpaths upon view change is selected on the Centerline page of the File > Options dialog, you can view the part and the toolpaths dynamically, otherwise the toolpaths are erased when you change the view.
2D — The top view of the part is displayed, and the toolpaths are simulated in different colors. You cannot change the view during the simulation. When the simulation is complete, you can change the view, but the toolpaths are erased.
3D — A 3D simulation of the part is displayed in the current view. You can dynamically change the view at any point during or after the simulation. The simulation does not have to be recalculated, so the view change is instant.
RapidCut — You can view this simulation dynamically. For zooming, the image must be recalculated, but this calculation time is quick. For panning or rotating, the image does not have to be recalculated, but a lower resolution version is displayed while you are transforming the part. This lets you change the view more interactively.
MachineSim — A 3D simulation of the part and the machine is displayed in the current view. You can dynamically change the view at any point during or after the simulation. The simulation does not have to be recalculated, so the view change is instant.