UnrealEngineUWP/Engine/Documentation/Source/Gameplay/DataDriven/DataDrivenGameplay.INT.udn

Availability:Public
Title: Data Driven Gameplay Elements
Crumbs:%ROOT%, Gameplay
Description:Driving gameplay elements using externally stored data.
version: 4.9

[TOC(start:2)]

Data driven gameplay helps mitigate the amount of work and complexity involved, as well as providing 
the ability to visualize and parameterize data creation and progression, for games that have an extended 
lifetime well beyond that of a typical boxed game, and require constant tweaking and balancing of data 
based on player feedback. The ability to move data out to **Microsoft Excel** or other spreadsheet documents that can be 
maintained using proven tools and then imported to automatically take effect in the game.

There are two new ways that data can be imported into UE4 through Excel documents:

* **DataTables**
* **CurveTables**


These Excel documents are .xlsm (macro enabled Excel documents) that have macro based export 
buttons to enable easily exporting to the intermediate data format, comma separated variables (.csv). 
These documents all reside in a single location to help make data easy to find and modify.

* [](Example.xlsm) (**Right-click** and **Save as...** to download)


## Data Tables

DataTables, as the name implies, is a table of miscellaneous but related data grouped in a meaningful 
and useful way, where the data fields can be any valid UObject property, including asset references. Before a designer can import a 
CSV file into a DataTable, a programmer has to create the row container telling the engine how to interpret the data. 
These tables consist of column names that have a 1:1 mapping to a given code based UStruct and its variables, 
which must inherit from **FTableRowBase** to be recognized by the importer. 

The first column is expected to be named Name and contains the names by which each row is accessed for use in game. Subsequent columns 
have a variable name for a heading and below, in the same column, the data for that row/column intersection. Given this 
format, a single row maps 1:1 directly to the structure inherited from FTableRowBase.

### Example

As an example, here is a definition for level up experience data and the CSV document that supplies the data to the game:

	/** Structure that defines a level up table entry */
	USTRUCT(BlueprintType)
	struct FLevelUpData : public FTableRowBase
	{
		GENERATED_USTRUCT_BODY()

	public:

		FLevelUpData()
		: XPtoLvl(0)
		, AdditionalHP(0)
		{}

		/** The 'Name' column is the same as the XP Level */

		/** XP to get to the given level from the previous level */
		UPROPERTY(EditAnywhere, BlueprintReadWrite, Category=LevelUp)
		int32 XPtoLvl;

		/** Extra HitPoints gained at this level */
		UPROPERTY(EditAnywhere, BlueprintReadWrite, Category=LevelUp)
		int32 AdditionalHP;

		/** Icon to use for Achivement */
		UPROPERTY(EditAnywhere, BlueprintReadWrite, Category=LevelUp)
		TAssetPtr<UTexture> AchievementIcon;
	};


**CSV Document:**

	Name,XPtoLvl,AdditionalHP,AchievementIcon
	1,0,0,"Texture2d'/Game/Textures/AchievementIcon1'"
	2,1000,9,"Texture2d'/Game/Textures/AchievementIcon2'"
	3,1000,10,"Texture2D'/Game/Textures/AchievementIcon3'"
	4,1500,12,"Texture2D'/Game/Textures/AchievementIcon4'"
	5,2000,14,"Texture2D'/Game/Textures/AchievementIcon5'"

[REGION:tip]
The double quotes around the asset type are important for the property importing pipeline. Without them, the text is imported as Texture2d'. 
[/REGION]

## Data Curves

Data Curves work in a somewhat similar manner to DataTables, however they only support floating point 
types. As with DataTables, the first column is named Name and contains the names by which each row 
is accessed for use in game. Each column heading after the first stores the X-axis variable for a 
curve to be plotted. The data under this heading is the Y-axis value for the given row. Given this 
format, a single row corresponds to a curve that code can access and interpolate data along.

### Example

Here is an example table for damage progression:

[REGION:simpletable]
|                      | 0   | 1   | 2   | 3   |
| -------------------- | --- | --- | --- | --- |
| Melee_Damage         | 15  | 20  | 25  | 30  |
| Melee_KnockBack      | 1   | 2   | 4   | 8   |
| Melee_KnockBackAngle | 10  | 45  | 60  | 65  |
| Melee_StunTime       | 0   | 1   | 5   | 7   |
[/REGION]

## Importing Process

Importing a CSV file is a simple process:

1.	Save your file out of Excel or another spreadsheet software with the .csv extension.
2.	Open Unreal Editor, and click on **Import** in the **Content Browser**.
3.  Navigate and select the CSV file you want to import as a DataTable.
4.  Finally, choose the row representation from the drop down list, in this case, LevelUpData.

	![](levelupdata_options.png)

	This creates a DataTable object in the current directory of the **Content Browser**.

	![](datatableobject.png)

	You can view the contents of the DataTable in the editor by **Double-clicking** on the object. You can update the object by **Right-clicking** on the object and selecting **Reimport** from the menu. 
	Note that the original file path is used when reimporting the object. Here is the view of the data just after importing:
	
	![](datatableview.jpg)

## Data Hookup

Hooking up data from these tables is quite easy. From a programmer's perspective, all you must do is 
place a Blueprint-exposed variable of either **FDataTableRowHandle** or **FCurveTableRowHandle**, 
depending on if you want a DataTable or CurveTable, respectively. From a content provider's point of 
view, this will expose a data field with two subfields:

1.	DataTable/CurveTable - this is the content reference to the table that holds the data.
2.	RowName - this is the name in the first column of the row you wish to get data from.


## Data Usage (Programmers Only)

Once you have the data hooked up, using the data is quite simple. The handle structures provide helper 
functions (**FindRow()** and **GetCurve()**) that allow you to retrieve either a struct or curve filled with data. 
In the case of a FCurveTableRowHandle, an FRichCurve pointer is returned. The FDataTableRowHandle, however, 
allows you to specify a structure in the template function call. This structure can be the final structure 
or any of its parents in the inheritance hierarchy.

One final note is that all structures and curves returned should not be cached further than the local scope 
of a function. This is to ensure that if the table is refreshed via re-import, the data changes take effect 
immediately and that no invalid pointers are accessed.

In the above DataTable example, the asset that is referenced is a lazy loaded asset (TAssetPtr handles this). 
If the Asset field type was set to UTexture, all of the assets would be loaded whenever the DataTable was loaded.