## Setting Physical Materials

DMM Physical Materials have nothing to do with Maya surface materials. A Physical Material is a set of parameters that control how a simulated object behaves. A Physical Materials library is included with the plugin.

The plugin will load all the Physical Materials library files in the folder specified in the preferences. Use the DMM preferences (under the "DMM Scene" menu) to the change the path to that folder.

DMM objects are created with the default DMM material, named defaultDmmMaterial1. If it already exists, it will be shared between DMM Objects. In the "DMM Material" menu, use the "Assign New DMM Material" menu list to create a new DMM Material and assign it to the selected DMM Objects.

Every Physical Material in the scene has a corresponding node of type DMMPhysMaterial. A physical material used in the scene can be modified via the Attributes Editor. To select the Physical Material node of a DMM Object, select that DMM Object and then open the DMM Asset Manager and click on the "Select" button next to "DMM Material Node". Or select the DMM Object and click on the appropriate icon on the DMM shelf.
Once the DMM Material node selected, it is possible to modify its attributes.

Sliders with an "adj." check box on the side affect the attribute value in an exponential way. Checking the "adj." box will cause the slider to linearly modify the value, but just a few percent around the current value. In this mode the slider always moves back to the center.

Here is a short description of the material attributes.

Youngs (stiffness) | How stiff a material is - larger values mean stiffer, smaller values mean more elastic
Youngs Damp | How much energy the material dissipate as heat when under stress
Poissons (volume preservation) | How is volume preserved when objects stretch - zero means perfect volume preservation, positive values mean volume increases when stretched, negative numbers mean volume decreases when stretched (cartoon like)
Density | How many kilograms per meter cubed the material has - defines the weight
Toughness | How easily does the object fracture. Bigger numbers are tougher. Zero is a special case, it means unbreakable.
Yield (plastic deformation start) | How far the material must deform before it stays deformed (values 0 to 1)
Max Yield (deformation limit) | Maximum amount of plastic deformation beyond which it will spring back (values 0 to 1)
Creep (plastic deformation speed) | How fast a material can deform and stay deformed (how fast it can plastically deform) (values 0 to 1)
Friction | Friction coefficient. Smaller numbers are more slippery.
Wakeup Radius | If the object is resting, it's how far (in meters) around an impact point will the object be affected on impact

Wakeup Radius, Min Iter, Max Iter, Split Limit and Relative Error are used to control and optimize the amount of time consumed by the simulator.

To remove unused DMM material nodes from the scene, use the "Delete Unused DMM Material Nodes" menu item (under the "DMM Material" menu).

For more on the meaning of the DMM Physical Material attributes read DMM Material Editing DMM Physical Material attributes can be keyed so to change over time.

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