Tracking Volume IDs using mapdl.vovlap

[VHB4910]

I have a solid geometry which is constructed using $N$ volume geometry primitives. They are assigned volume ids by MAPDL in the sequence the $N$ volumes are created:

mapdl.geometry.vnum
=[1,2,...N]

Now, for conformal meshing I wish to overlap all these individual volumes:

mapdl.allsel()
mapdl.vovlap("ALL")

Clearly, this boolean operation creates new volume IDs.

1. Is there a way to track the new volume IDs to the original volume IDs?

2. Or is there an option to ""Keep"" the original volumes/IDs like there is such an option in mapdl.vsbv:

mapdl.vsbv("Vol1","Vol2", keep1="KEEP", keep2="KEEP")

[VHB4910]

I think using mapdl.boptn worked for retaining the old volumes and IDs.

mapdl.boptn("KEEP","YES")
mapdl.allsel()
# Overlap volumes
mapdl.vovlap("ALL")

But, when I use the old volume IDs to mesh the volumes separately, I do not get a conformal mesh (nodes of volumes sharing an area does not coincide).

[mikerife]

@VHB4910 well that makes sense as the original volumes were meshed and not the new volumes. Since you are selecting the set of volumes to overlap, and using 'all' as the list, use mapdl.geometry.vnum to return an array of volume IDs after the overlap.

mapdl.allsel()
mapdl.vovlap("ALL")
volumes = mapdl.geometry.vnum

Tracking the IDs after a Boolean can be difficult as both the topology and geometry are used to assign new IDs. Plus available ID numbers are used, so there could be gaps etc depending on the state of the model at the time of the Boolean. Plus a Boolean can result in the same or different number of entities as before the Boolean.

[VHB4910]

I see.

Its just that I was using mapdl.geometry.volume_select to select volume entities for assigning material properties and later creating element & node lists so wanted to stick to the original IDs or get a map from the original IDs to the new ones.

[germa89]

As @mikerife mentioned, on booleans operations the IDs cannot be traced back uniquely. The best way to re-match the old volumes (with the new ids) is to perfom new subentities selection... aka selecting an area or keypoint (based on location) we know it should be contained by that volume, and obtain the volume from it.

For instance:

mapdl.ksel("S","loc", "x", 0)
mapdl.lslk()
mapdl.asll()
mapdl.vsla()