TMAP for Blueprints

General Feedback & Requests
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1

So, here TMap's in Blueprint - Blueprint - Unreal Engine Forums we were asked to make a new thread if this is needed (2014). That thread is the first google hit, I don’t know if there is something more current.

Basically, asking for an implementation of dictionary/tmap for blueprints. there are many algorithms that rely on it and while it can be emulated with two arrays, the performance is terrible.
For a specific use case, here something from my Project, as it may well be among the worst there are. I have a Tilemap, where I want to remove/add tiles, and neighbour tiles have blended states (They change depending on their surrounding). So, when a change happens, the 4 surrounding tiles need to be checked and may need to be changed too.

Now I’ve done this in the past with a different project, in this case Python/Pygame. I had a Data Structure like this:
{(Bool, Bool, Bool, Bool) : SubSurfaceRef}

Where the Bools are the 4 neighbours existing and then the texture that should be set based on these.

I have found no way to do this well in UE4 Blueprints. C++ would be an option, if one doesn’t target HTML5/Mobile.

So, my current way, a Data Table:

895×400 65.5 KB

Then iterate over the thing:

1180×320 76.3 KB

Check if it’s the right entry:

555×696 104 KB

And then set the tile.
For 64 Tiles this took my computer ~5.5 seconds to run through in editor.
The old Python system took less than 1ms.

Implementation Idea:
A variation of Data Table, where one column can be set as key and we can retrieve a row by key in Blueprints.

Edit: I optimized into acceptable margin by using Find, which I appear to have overlooked. Still a dictionary would speed up the algorithm from O(n²) to O(n)

2

Until/unless TMap is implemented in BP, you could create methods in your BP’s base class to retrieve and set elements from the TMap that you need. It’s a cludgy workaround, but it’s doable.

//.h

UPROPERTY()
TMap<FName, ATile*> TileMap;


UFUNCTION(BlueprintCallable, Category = "Tilemap")
ATile* GetTileFromMapByName(const FName& TargetTileName);

UFUNCTION(BlueprintCallable, Category = "Tilemap")
void SetTileToMapWithName(const FName& TargetTileName, ATile* TargetTile);


//.cpp

ATile* GetTileFromMapByName(const FName& TargetTileName) {
    return TileMap.FindChecked(TargetTileName);

   //--OR--
   if (TileMap.Contains(TargetTileName) {
      return * TileMap.Find(TargetTileName);

    }
    return NULL;

}

void SetTileToMapWithName(const FName& TargetTileName, ATile* TargetTile) {
    TileMap.Emplace(TargetTileName, TargetTile);

}

“C++ would be an option, if one doesn’t target HTML5/Mobile.”

I don’t understand this; is there something about HTML5/Mobile that prevents you from accessing custom C++ classes? Blueprints are rooted in C++, how do they work in HTML5/Mobile at all if not via C++?

Regardless, I agree. I’d very much like to see TMap available in BP.
TSet as well.

3

Ah, should have googled some more before posting. Building for iOS gave me a this feature does not exist for code projects. After some digging I found out that you need a mac to build C++ projects for iOS. And as for HTML I kind of assumed that C++ is a no go, which to be fair, it is. It’s just cross compiled to JS ( Developing HTML5 Projects | Unreal Engine Documentation )

So yeah, disregard the C++ sentence, it very much is an option. I still stand by the point that this feature would do well in blueprints though.

4

“I still stand by the point that this feature would do well in blueprints though.”

Wholeheartedly agree.

5

After some digging, it seems like this feature might come in .15:

But the info in that ticket is very vague.
So @Epic, any chance of some more elaboration of how the implementation might look like?
In my case, I have one instance where I get a TileMap(Value) by a custom 2D int vector(Key). If this is possible in blueprints soonish, I could save a lot of time moving onto other things and finishing that once C++ is not necessary.