twod
See the COP2_MultiImageWipe example in HFS/toolkit/samples/COP2 (where HFS is your Houdini install location). It gives an example of how to use that signature. You basically grab the TIL_Plane by name from the TIL_Sequence returned by inputInfo(N), where N is the input you're interested in, then pass that to inputRegion(N, context, plane, …).
Seems like I have to use COP2_multibase? but it really solved my problem,
thanks a lot.