Creates a new time-dependent multibody list based on an existing multibody list, by selecting at each time only those multibodies in the existing list that have at least <threshold> constituent beads lying within a specified rectangular prism within the box. This check is done separately at each time in the trajectory such that the resulting multibody list will differ by time.
region_multibody_list <name of new multibody_list to create> <name of existing multibody_list to downselect geometrically> <xlo> <ylo> <zlo> <xhi> <yhi> <zhi> <threshold>
<xlo> <ylo> <zlo> <xhi> <yhi> <zhi> set the lower and upper bounds of the domain to be selected in the x,y, and z directions. Note that this command does not actually create any new multibodies - it merely creates a new list downselected from an existing list of multibodies.