Using this method you will renumber the rectangular regular array of elements or quads in two perpendicular directions in a user defined coordinate system (Cartesian or cylindrical). A local coordinate system must be created to match the two primary numbering directions.              

Before element renumber        

After element renumber: X increment by 1, Y increment by 100    

The element and node renumbering option is based on element/node connectivity directions instead of local system directions.

Using this method you must select the start element (or node) and the adjacent connected elements (or nodes) to indicate primary and secondary directions. These elements need to be connected. This method works only with quadrilateral elements (without any triangular elements) and should have a mapped (regular) pattern.    

Adjacency based renumber

Element renumber

Node renumber

The tolerance is used to group the nodes/elements in the correct order for renumbering. For example, if you have a simple structured mesh with nodes distanced 5 mm on the local X direction and 2 mm on the local Y you want to renumber the nodes so that it starts with 101 for the starting ID. Then increment in local X direction by 1 (for example 101, 101+1, 101+2, and so on) and in local Y direction by 10 (for example 101, 101+10, 101+20, and so on).  

If you use the correct tolerance of 1 mm (which is <5 mm and < 2 mm nodal distances) here is the result:

In a real scenario you rarely get meshes like the example above, so the distances between nodes are variable like the image below. You want to renumber it with the same objective and tolerances (1mm).

The result is:

As you can see in the image above the renumbering is not done properly. This is because the smallest nodal distance is 0.5 mm which is smaller than 1 mm tolerance. If you reduce the tolerance to 0.1 mm you will get the correct result.