[C++]: Select a player with a mouse click.

Development Programming & Scripting C++
1

Hi guys,

I’m trying to figure out the best way of selecting any character in my game with a mouse click. But i’m a little stuck. The basic gist of it is:

  • On mouse click - do raycast [done]
  • Deselect anything currently selected [done - will need to change this later so that it only does it if no players are hit.]
  • If raycast hits, check if it’s a playerpawn. [done]
  • If it’s a playerpawn, run a check to see which team they’re on. [done]
  • Now we know which team they’re on, find their number in the player array. [stuck ]
  • Assign this number to the SelectedEnemy or SelectedFriendly ints for future use [can do after above step is complete]
  • Apply fresnel effect based on selected player, only to selected player, and only visible on client end. [again, can do after above step]

I’ve pasted the relevant functions into this pastie: http://pastie.org/private/apqx0s8x9jj9pdkcnxbisa

Anybody have any ideas on the cleanest way to do this?

2

There’s actually a function you can use to get this easily; returns -1 if the instance is not in the array, otherwise returns the index.

3

Not sure i understand your problem but in a effort to help.
If you have done the trace and it returns the Pawn/ Character get the controller of the pawn.
In the Player State of the controller is the member UniqueId and PlayerId.

See doc for more info.
GetPlayerControllerFromNetId
APlayerState::
APawn::GetController
AController::GetPawn

Hope it helps. :slight_smile:

4

Ah okay, so it looks like this may be correct then?


void ASmashyCharacter::SelectPlayer(AController* SelectedPC)
{
	//is the selected enemy friendly or enemy?
	bool bIsEnemy = IsEnemy(SelectedPC);

	//now find the player number in the array.
	uint32 SelectedPlayer = SelectedPC->PlayerState->GetUniqueID();

	if (bIsEnemy)
	{
		SelectedEnemy = SelectedPlayer;
	}
	else
	{
		SelectedFriendly = SelectedPlayer;
	}

	UpdateTargetColorsAllMIDs();
}
5

Yes thats seems correct to me, can`t test it atm.
But now SelectedPlayer has the ID of the controller.
So you can do what ever you want with it now.

Glad i could help out :slight_smile:

6

Thanks for your help . This is the better way to do it btw:



APlayerState* SelectedPlayer = SelectedPC->PlayerState;

	if (bIsEnemy)
	{
		SelectedEnemy = SelectedPlayer;
	}
	else
	{
		SelectedFriendly = SelectedPlayer;
	}

This stores the actual playerstate object rather than player ID, which apparently can change.

7

Thats intresting and very good to know, do you have a link or something to any documentation on that?

8

No real documentation as such i’m afraid, i was just going by the comments from people in #unrealengine IRC channel.

So 's the current state of my initial function for getting a target:



void ASmashyPlayerController::GetPlayerTarget()
{
	//cast our own player pawn for reference.
	ASmashyPlayerState* Player = Cast<ASmashyPlayerState>(PlayerState);
	ASmashyCharacter* PlayerPawn = Cast<ASmashyCharacter>(Player);
	//deselect anything already selected.
	PlayerPawn->Deselect();

	//Trace to see if anything is behind the mouse cursor
	FHitResult Hit;
	GetHitResultUnderCursor(ECC_Pawn, false, Hit);

	if (Hit.bBlockingHit)
	{
		//it is a player, check what team they're on.
		ASmashyCharacter* TestPawn = Cast<ASmashyCharacter>(Hit.GetActor()); /// works until this point.
		AController* TestPlayer = TestPawn->GetController();
		//select player as enemy target
		PlayerPawn->SelectPlayer(TestPlayer);
	}
}

Maybe i’m doing this wrong, i was under the assumption that this:


GetHitResultUnderCursor(ECC_Pawn, false, Hit);

would run a line trace for what is clicked under my cursor, and will check to see if it was a pawn. however the game breaks and TestPawn = NULL. any ideas?

9

Am not sure about that method, GetHitResultUnderCursor()

Looking at the sample code in the doc it dont look like its doing the trace in 3D space at all.


bool APlayerController::GetHitResultUnderCursor(ECollisionChannel TraceChannel, bool bTraceComplex, FHitResult& HitResult) const
{
    ULocalPlayer* LocalPlayer = Cast<ULocalPlayer>(Player);
    bool bHit = false;
    if (LocalPlayer)
    {
        FVector2D MousePosition;
        if (LocalPlayer->ViewportClient->GetMousePosition(MousePosition))
        {
            bHit = GetHitResultAtScreenPosition(MousePosition, TraceChannel, bTraceComplex, HitResult);
        }
    }
 
    if(!bHit) //If there was no hit we reset the results. This is redundent but helps Blueprint users
    {
        HitResult = FHitResult();
    }
 
    return bHit;
}

I think you have to convert the screen space to world space and then do the trace.
Found a AnswerHub post on this .

10

Hmmm… that’s interesting. GetHitResultUnderCursor() is used in the top down example game, that’s where i got it from.

Looks like i may need to set up a custom trace, which is annoying.

11

I’m using the following function on my pawn and is working for me:


void AMyRTS_Pawn::OnLeftMousePress(){
	bLeftMouseDown = true;

	FHitResult Hit;
	Controller->CastToPlayerController()->GetHitResultUnderCursor(ECC_Pawn, false, Hit);

	if (Hit.bBlockingHit){
		if (Hit.Actor != NULL){
			Selected = Cast<ACharacter>(Hit.GetActor());
			GEngine->AddOnScreenDebugMessage(-1, 5.f, FColor::Magenta, FString::Printf(TEXT("Character Selected!")));
		}
	}
}

You are correct about the ECC_Pawn, it can get both actors and ground location.
Try checking if your Hit found an actor before casting, this will make sure its not a failed cast.