With this record you can specify a data item which should be changed over time. The time table should be given in the change_dataitem_time table as time-value sets; at least two sets should be specified.
The operat determines how the time-value sets are used. If operat is set to -use, then the value of the time-value sets is directly used. If operat is set to -add, then the value of the time-value sets is interpreted as a rate of change, so that the value is multiplied with the time step and then added to the old value.
As a typical example you can use this to prescribe the displacement of a contact geometry over time. Below the y-coordinates of a geometry line which is used in the contact algorithm is changed over time:
contact_geometry 0 -geometry_line 1
geometry_line 1 0. 10. 2. 10.
change_dataitem 0 -geometry_line 1 1 -use
change_dataitem_time 0 0. 10. 100. 0.
change_dataitem 1 -geometry_line 1 3 -use
change_dataitem_time 1 0. 10. 100. 0.