Choosing what game objects should be assigned to each LOD Group on each Grouping is very important, and special care must be taken when your scene contains a mix of game objects that need to be assigned to different LOD Groups and/or Groupings (although, don't worry too much if you mis-assign something. You can always re-assign it to the correct Grouping/LOD Group later)!
There are multiple options available to you that change how the objects are selected. Please take a look at the Assignment Operations Section for detailed information on each option.
Within the World Designer Tool, these options can be found within the Assignment Settings tab of the Advanced Operation Settings Control Window.
Whatever objects are chosen for the assignment, please keep the following in mind:
1) The Assignment Operation cannot be used on Game Objects that are the root Asset Chunks belonging to Cells. If you try to assign these objects, and error message is shown in the Console Log.
2) When assigning an object that belongs to a prefab instance hierarchy, the outermost root is unpacked (unless the prefab instance is an Asset Chunk) using PrefabUtility.UnpackPrefabInstance (and PrefabUnpackMode set to OutermostRoot). With that said, if the object you assign is itself a prefab instance, it will remain a prefab instance under the new Asset Chunk.
3) Assigning works just like dragging an object onto a new parent game object in that all of the objects descendants are carried along for the ride.
We recommend starting your Assignments with a single object (by using the Selected Objects option and selecting a single object). Make note of which Cell you believe the object will be assigned to, and after the Assignment Operation is completed, verify that the correct Cell has been enabled and Asset Chunk created.
Next move on to a larger but still small subset of objects, perhaps this time choosing ones that fall in multiple different Streamable Cells. Again, pre-determine which Cells should be enabled and which Asset Chunks should be enabled, then after the Assignment Operation completes, verify.
If the objects are not being assigned to what you believe to be the correct Streamable Cells, please check out the Assignment Issues Section to diagnose why.
Once you have done this a few times with larger and larger groups of objects, and verified that everything is working correctly, you can run a final Assignment Operation that assigns the remaining objects for the given LOD Group and World Grouping (assuming that is possible given the hiearchy of your scene).
Now, please take a look at the Final Words Section for some final advice and things to look out for.
--Sample Scene Directions--
When assigning the Terrain game objects, start by using the Selected Objects option and selecting Terrain1. After you run the Assignment Operation (by pressing the A* button), you should see Cell R1 | C1 turn blue and the Terrain1 object disappear from the scene.
Click on this Cell in the Cell Viewer area and press the L* button. The terrain should be loaded into the scene, either as a prefab or as an additional scene (depending on how your Asset Creator is configured), but note how Terrain1 is now a child of an empty game object. This empty game object is the actual root Asset Chunk, and as you can see its name follows a predictable naming convention which means it is part of an Asset Chunk Set.
If the terrain was successfully loaded, we have success! You can proceed by selecting the remaining Terrains (Terrain2, Terrain3, and Terrain4), and running another Assignment Operation. All four terrains can now be loaded and unloaded from the scene very easily using the World Designer Tool, using the L* and U* buttons.
For the other Groupings, you can play around with the other What To Assign options in order to get familiar with them. For example, with Grouping 2 and 3 you can try out the Children Of Parent option, being sure to drag the Large Structures and Plants game object into the Assignment Parent field before running the Assignment Operations.
For Grouping 4, try the Regular Expression Matches option, with the Regex Pattern field set to ^Capsule (make sure to clear the Assignment Parent field before running the operation). After running this Assignment Operation, load Cell R14 | C2. Take note of how the Capsule (11) child hierarchy was kept in-tact, depsite the children also having names starting with Capsule. This is because the search method works top down, and once a game object is matched (in this case, Capsule (11)), none of that game object's children will match (but will be dragged along with the parent when it is assigned).
After successfully assigning the assets for all four Groupings, you can delete the World Assets game objects from the scene, as it is no longer needed. You should now be able to enter Play mode and see your World come to life!