Global Element IDs

Trelis Mesh Entity ID Spaces

All mesh entities have an ID associated with them which is unique within the corresponding mesh entity ID space. For example, a hex will have an id which can be used in commands such as "list hex 17". However, this ID is only unique amoungst the hexahedra in the Trelis session. There could also be a tet, quad, tri, edge, node, etc. with ID 17.

Global Element IDs

Whenever a hex, tet, quad, tri, etc. gets put into an element block, it is assigned another ID which is called the Global Element ID. The Global Element ID is unique amoungst all element which have been put into any block. Starting in Trelis 14.0, it is exported to the Exodus file format so that downstream analysis applications can map elements back to the corresponding Trelis hex, quad, etc. In Trelis 14.0, Global Element are not supported by the other exporters, but will be in future releases.

Interacting with GlobalElement IDs

After a hex, quad, etc. is placed into an element block, you can see which ID was assigned to it with the list command. For example:

bri x 10
mesh vol all
block 1 hex all
list hex 1

The resulting output will contain the following:

Trelis> list hex 1
Hex 1
Global Element ID = 1

In this simple example, the Hex ID is the same as the Global Element ID, but this will not always be true.

These Global Element IDs are exported as the global id in the Exodus file. If during an analysis run, a particular element needs to be identified back in the Trelis session, they can be found with any of the following commands:

List element <id_range>

Draw element <id_range>

Highlight element <id_range>

List element <id_range>

Users can control the assigned Global Element ID with the renumber command.