The Transfer Operation will essentially transfer all child objects belonging to all Asset Chunks for a given Cell and LOD Group to another Cell on a different LOD Group (either on the same World Grouping or a different World Grouping).
There are two types of Transfer Operations available. The first, using the T* button, transfers objects from a single LOD Group. The second, using the Transfer All LODs button, trasfers the child objects from every LOD Group (for the currently edited World Grouping)
The Transfer Operation is just an Assignment Operation under the hood, where the objects to assign are sourced from the children of the Asset Chunks belonging to the selected Streamable Grid Cells (note, all children are transferred, vs an assignment operation which selectively assigns only a subset of matching game objects).
When using the T* button, only the Asset Chunks associated with that LOD Group are transferred, however when using the Transfer All LODs button, the objects from all Asset Chunks across all LOD Groups are transferred (for the current World Grouping being edited and only the selected Cells).
The World Grouping and LOD Group that the objects are transferred to is determined by the Transfer Grouping and Transfer LOD (only when using the T* button) settings found in the Advanced Operation Settings window and Transfer Settings tab.
Because it is just an Assignment Operation under the hood, the same rules apply for determining which Streamable Cells the transferred objects will be assigned to. That is to say, if Try Use Mesh Bounds is enabled (under Advanced Operation Settings/General Settings), the center of each game object's mesh bounds is used to calculate the cell the object will be transferred to. If that option is disabled or the game object does not have a mesh to use, the position of the Game Object is used instead.
Note that it is perfectly valid for the Transfer Grouping and Transfer LOD to be the same Grouping and LOD that the Transfer Operation was initiated for, which can be used to confirm that Game Object children belonging to those Cells have been assigned correctly.
In order to use this operation, the Transfer Grouping you choose must have the same number of LODs as the current Grouping To Edit (i.e., source grouping)!
If it seems like an object is not being transferred to the correct Streamable Cell based on your observation, there are several possible reasons why it might be happening. Please take a look at the Assignment Issues Section from the FAQ for more information!
One of the main use cases for using this operation is for modifying any settings on a Streamable Grid that would invalidate which Cell's child game objects are placed in. For example, if you were to halve the number of rows on the Streamable Grid, but double all rows sizes, the total length of all rows remain be the same. However, any child game objects that were previously in Row 2 would now be in Row 1, objects in Row 3 & 4 would be in Row 2, and so on. In addition, since we have halved the number of rows, any Rows larger than half the previous number of Rows would be invalid!
Note, this is just one example; there are many modifications to the Streamable Grid that can invalidate the placement of child objects in Cells.
In order to avoid these issues and make such changes to a Streamable Grid, it's necessary to follow these steps:
1) Duplicate the Streamable Grid who's settings you wish to change.
2) Rename the Grid asset to differentiate it between the original Grid asset.
3) Give each LOD a slightly different Group Name. This is necessary to avoid name clash collisions when performing the Transfer Operation.
4) Make the changes you need on the new Streamable Grid.
5) Disable all Cells on the new Streamable Grid. The Transfer Operation will automatically enable Cells as needed.
6) If any LOD uses Multi-Chunking with variable per Cell values, reset the number of Chunks for all Cells to 1.
7) The Transfer Operation will generate new Asset Chunks for the new Streamable Grid. If you wish for these Asset Chunks to be placed in a separate folder than the Asset Chunks from the old Streamable Grid, perform steps 8 and 9; otherwise, proceed to step 10.
8) Modify any Extra Data (Global or LOD specific) on the new Streamable Grid that references folder location to point to the new folder you want the Asset Chunks to be created in.
9) Duplicate each LODs Asset Creator (if each is using a unique one) and assign new folders for each one.
10) Add a new World Grouping to the World Component and assign the new Streamable Grid to it. Configure this World Grouping to match the World Grouping the old Streamable Grid is assigned to (use same Chunk Manager, Chunk Streamer, settings, etc.). Note that we do not want to remove or otherwise modify the old World Grouping, as it will be needed to perform the Transfer Operation.
11) Launch the World Designer Tool and set the Grouping To Edit to the new World Grouping you created in step 10.
12) Assign an Asset Creator to each LOD on the new World Grouping. This may be the duplicate asset creators you created in step 9, or it may be the same Asset Creators used by the old World Grouping.
13) If using Multi-Chunking, set the Max Children/Chunk values for each LOD on the new World Grouping. Usually, you will want to use the same values that the old World Grouping is using.
14) Change the Grouping To Edit to the Grouping with the old Streamable Grid. We recommend enabling Auto Disable and Auto Destroy at this time (if not already enabled).
15) Change the Transfer Grouping to the new World Grouping with the new Streamable Grid.
16) Select a single Streamable Cell and press the Transfer All LODs button. This operation will cycle through each LOD on the Grouping being edited and transfer child objects from the selected Cell's Asset Chunks to Asset Chunks on the Transfer Grouping's equivalent LOD. This is equivalent to performing a Transfer Single LOD operation on each LOD individually.
17) If you have Auto Disable enabled, once you perform the transfer operation on all LODs for the Cell, that Cell on the old World Grouping should be disabled. If is not disabled, it is an indication that something went wrong with the Transfer Operation.
18) Additionally, if Auto Destroy is enabled, once you perform the transfer operation on all LODs for a Cell, all Asset Chunks associated with the Cell from the old Streamable Grid should be deleted from the Project (if a scene, the scene should have also been removed from the Build Settings window). If they are not destroyed/deleted, it is an indication that something went wrong with the Transfer Operation.
19) Once the Transfer Operation has been completed, you should switch the Grouping To Edit to the one with the new Streamable Grid and try and load different LOD Assets from the Cell, to ensure that all child game objects have been transferred successfully and that the Cell has been configured correctly.
20) If you have confirmed that the Transfer Operation was 100% successful, you can continue transferring objects. We recommend starting with only a few Cells selected and confirming everything works okay before moving onto larger groups of Cells; and of course, it's important to select too many Cells at once for performance reasons!
21) If you have confirmed that the Transfer Operation was 100% successful for all Cells, you can close the World Designer tool and remove the old World Grouping from the World Component. At this time, you should move the new World Grouping to take the place of the old one, which will ensure compatibility with Active Grids.
22) Remove the old Streamable Grid asset. If you duplicated Asset Creators in step 9, you can also delete the old Asset Creators at this time.
23) If Auto Destroy was not enabled during the Transfer Operations, you will have Asset Chunks associated with the old Streamable Grid left behind in your project. You can safely delete those assets now.
--Watch Out!--
If you have resized your Streamable Grid Cells, it may be tempting to perform a Transfer Operation from a World Grouping to itself for all LODs.
We must say with absolute clarity, DO NOT DO THIS! Use the steps outlined above, no matter whether you think it is necessary!