This Section introduces some basic concepts you will need to understand in order to utilize the World Designer Tool. Enjoy!
The Origin is the base position of the World, which may be the position of the game object that the World Component is on or a set Vector3, all of which is configured within the Origin Settings tab on your World Component.
The Origin Cell, on the other hand, is unrelated to the Origin Cell set on the World Component, in order that the editing operations do not affect the in game representation of your World. This Origin Cell is always in reference to the Base World Grouping!
The Origin Cell is always placed at the Origin within the Scene View, while other Cells are placed offset in reference to it. You can change which Cell is used as the Origin Cell at any time, and doing so will automatically update the position of any loaded Asset Chunks. For larger Worlds, changing the Origin Cell is a powerful feature that allows you to keep the assets you wish to edit close to the origin.
Whenever you save or update a World Region, the currently set Origin Cell is saved with the World Region data. If the World Region is used at runtime, this Origin Cell data can either be utilized or ignored, however when loading a World Region via the World Designer Tool, the Origin Cell is always set to the Origin Cell in the World Region data. This ensures that Asset Chunks associated with the World Region's Cells are always loaded close to the Origin.
Because updating the Origin Cell can be a hefty operation, we require you to press a button (called Update Origin Cell/Position) in order to initiate the update operation. Since it is possible for the Origin Cell sliders to reflect values different than the actual Origin Cell currently in use up until that button is pressed, we have added the actual Origin Cell in parenthes next to each Axis (e.g., next to Origin Row is the currently set Origin Cell).
Speaking of World Regions, they are a unique feature of the World Designer Tool that allow you to define, load, and unload specific LOD Asset Chunks for multiple Streamable Grid Cells with very little effort. Not only is this useful for editor work, these World Regions can be saved to World Components in order to be used at runtime! This offers an alternative to the traditional Active Grid based approach to loading World Cells. World Regions are explored in greater detail in their designated Section within this Chapter.
In order to make working with different World Groupings as easy as possible, only a single World Grouping can be edited at a time while using the World Designer Tool. This Grouping is referred to as the Grouping To Edit and can be selected at the top of the Editing Controls tab.
With that said, changing between different World Groupings does not unload any Asset Chunks that have been loaded for other World Groupings, so you will still be able to see and make changes to those Assets. You just won't be able to load, save, or (in some instances) unload Asset Chunks using the World Designer for any World Grouping but the one being edited.
Each World Grouping's Streamable Grid may have several LODs associated with it, and the World Designer allows you to load whatever LODs you wish for each Cell on the Streamable Grid. In order to aid you in tracking which LODs are loaded for each Cell, LODs are color coded in the same way as LODs in the Loading Blueprint Editor.
Each set of 10 LODs use the same color hue with varying levels of saturation and brightness in order to help differentiate between LODs that are very close together. The saturation and brightness values have been pre-calculated for best results, however the hues used for each set of LODs is configurable via the Global Editor Settings asset.
A Cell can only have Asset Chunks for a single LOD loaded at a time. If you try to load Asset Chunks for an LOD while Asset Chunks for a different LOD are already loaded for that Cell, the currently loaded Asset Chunks are unloaded before the new Asset Chunks are loaded.
Multi-Chunking refers to the ability for a single Cell to make use of multiple Asset Chunks. Whenever a Cell is loaded, all of its Asset Chunks are loaded together but potentially across multiple frames. This allows the work of loading a Cell's assets to be spread across multiple frames, a tactic which can help eliminate lag spikes.
When you load LOD Asset Chunks for a Cell using the World Designer Tool, all Asset Chunks belonging to the Cell are always loaded together. The tool performs special checks to make sure these Asset Chunks continue to remain loaded, as they are intended to be treated as a single entity, even though they are actually separate Assets.
The World Designer Tool is configured to automatically adjust the number of Asset Chunks each Streamable Grid Cell uses as a result of a Destroy, Assignment, Transfer, or Evaluation Operation. This involves automatically creating or destroying Asset Chunks, moving child objects from one Asset Chunk to another, and adjusting the multi-chunk values for each Cell on the Streamable Grid asset. More information can be found in the Advanced Asset Operations Section within this Chapter.
Not all World Groupings are editable by the World Designer Tool. All of the following conditions must be met for a World Grouping to be editable:
1) The Grouping must have a valid Streamable Grid assigned to it in the World Inspector.
2) The Grouping must either be the Base Grouping (Grouping 1), or must be compatible with the Base Grouping.
3) At least one LOD on the World Grouping must be editable.
Furthermore, if the Base Grouping is not editable (a failure of 1 or 3 above), all other World Groupings will be considered uneditable and you will not be able to launch the World Designer Tool.
Just because an LOD exists on a World Grouping's Streamable Grid, it does not mean that you can edit the Asset Chunks belonging to it via the World Designer Tool. All of the following conditions must be met for an LOD to be editable:
1) The LOD must have a valid Chunk Manager mapped to it(this could be assigned to the LOD directly, or assigned to the World Grouping or World that the LOD belongs to).
2) The LOD must have a valid Chunk Streamer mapped to it (this could be assigned to the LOD directly, or assigned to the World Grouping or World that the LOD belongs to).
3) An Asset Manager must exists for the given Chunk Streamer.
4) The LOD must have the Use Single Chunk Set For All Cells setting disabled (found on Streamable Grid Asset).
5) The LOD must not have a Chunk Type of None (found on Streamable Grid Asset).
6) The LOD must have Use Positional Data enabled (found on Streamable Grid Asset). Note that this setting is enabled by default when the LOD has a Chunk Type of Unity Terrain.