## Playing a Simulation

DMM simulations are played just like Maya animations and Maya dynamics. To play a DMM simulation, click the Maya play button. The DMM simulator will not step forward more than 1/25 of a second, and it will not step backward. The DMM simulator allows the setting of a sub-step value. It is basically a multiplying factor for the frame rate. The default Maya play setting is 1/24 second with the default DMM sub-step is 8 so the simulation step is 1/192 second. Video games typically run at 1/30 or 1/60 second. Either of these frame rates can be set with a DMM sub-step of one in order to preview in Maya how DMM will look in a game. A more accurate simulation with better collision detection and better convergence for very stiff materials can be achieved with a higher sub-step value. DMM may behave differently with different frame rates and sub-steps.

The frame rate is set in Maya preferences under the settings category. The DMM sub-step is set in the DMM Scene node attributes panel via the Attributes Editor. To select the active DMM Scene node, click on the "DMM Scene >> Select Active DMM Scene Node" menu item.

The DMM Cache can be used in order to record the DMM simulation and play it backwards.

Notes: See DMM Scene Node for other important scene settings. Don't animate the mesh vertices of a Tet Cage! On the first frame of the animation, the Output Simulated Mesh shows the Tet Mesh as computed from the Tet Cage and the Output Surface Mesh shows the Input Surface Mesh clipped by the Tet Mesh. The DMM simulator has not kicked in yet, so no deformation nor fracture have occurred. Starting at the second frame, those output meshes show the result of the simulation done by the DMM simulator. The DMM simulator is only initialized once (at the beginning of the second frame). So it will always take into account the Tet Meshes computed from the Tet Cages as they are at this time. If the vertices of a Tet Cage are animated by Maya, even though the Tet Mesh will be automatically recalculated, it is a waste of calculation as the DMM simulator will not be updated with this new Tet Mesh. Therefore the result will not show during the animation playback.

Next: Combining DMM Simulation with Maya Animation