## DMM Passive Regions

DMM Passive Regions let you fix part or parts of a DMM Object in space or allow part to be animated by Maya (kinematically driven). It is possible to fix part of a DMM Object so that it won't move even when the rest of the object is simulated. If the object is animated via Maya then the fixed parts move as they are animated and the rest of the object movement is controlled by the simulator.

As a visual hint, the DMM Passive Region polymeshes are applied a semi-transparent green color. but they are not rendered (the Primary Visibility, Visible In Reflections and Visible In Refractions attributes are turned off). Just as any shape, a Passive Region can be deformed or scaled.

An easy way to define a passive part of a DMM Object is to use "DMM Asset >> Add New DMM Passive Region to DMM Object" menu item, or use the appropriate shelf icon.
This creates a polymesh cube and assigns it as a DMM Passive Region of the selected DMM Object. The created cube is of a unit size and centered with respect to the selected object. If multiple objects are selected, one DMM Passive Region is created and assigned to all of them. It's positioned at the geometric center of the bounding box encompassing the selected DMM Objects.

The cube can be moved, resized, and reoriented to place it around the part of the DMM Object that will not simulate. Any number of DMM Passive Regions can be added to an object and they can be shared between multiple DMM Objects.

It is important to note that the DMM Passive Regions define which vertices of the tetrahedral mesh will be DMM Passive. If no actual vertices fall inside a DMM Passive Region, the region will have no effect, even if it overlaps the Tet Mesh.

If a shape other than a box is preferred for a DMM Passive Region then any convex shape can be used. First select a polymesh, and then choose "Make Polymesh into DMM Passive Region" menu item, or click on the appropriate shelf icon.
The polymesh will be added as a passive region to the DMM Object. It is also possible to paint individual Tet Mesh vertices to be DMM Passive for exact control of the mesh. But this is not recommended because if the density of the mesh is changed later, then the vertices would have to be repainted.

If the DMM Object is animated by Maya, it is recommended to parent a DMM Passive region to the object so it will move with it.

Requirements for a DMM Passive Region Need to be convex Need to be made of one connected component DMM Passive Regions recompute at every frame. It makes it possible to animate a DMM Passive Region so to change with time what parts of a DMM Object are controlled by Maya and what parts are simulated.

Next: Glue Regions