How to detect if the player is facing an object?

Development Programming & Scripting
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1

Hi all.
I’m trying to detect if the player character is facing another object using dot product but I can’t seem to get the correct results. The dot product still returns a negative number when the player faces the object.

I’m using dot product instead of a line trace as I want to be able to set a vision arc.

Can you guys see what I’m doing incorrectly?

DEMO

dot
dot1264×372 71.5 KB

2

Try printing the forward vector on tick. I seem to recall it isn’t the same as the actor forward vector?

3

This just print’s out either 1 or -1 depending on which axis I’m facing.

4

If the dot product returns the inversed result, why don’t you switch the pins where you plug in your player and actor locations?

5

Here’s the code we use. Should be straightforward to translate to BP.

Looking at your BP might be that you aren’t normalizing both vecs? Not sure…

bool ABasePlayerController::GetIsActorInFrontOfPlayer(AActor* queryActor)
{
	if (queryActor && GetCurrentCharacter())
	{
		// get normalized player to target vec
		FVector playerToTargetVec = queryActor->GetActorLocation() - GetCurrentCharacter()->GetActorLocation();
		playerToTargetVec.Normalize();

		// get normalized player forward vec
		FVector playerForwardVec = GetCharacter()->GetActorForwardVector();
		playerForwardVec.Normalize();

		// get dot product of player to target vec and player forward vec
		// if dot product > 0 then query target is in front of player
		// using 0.1 because near zero is perpendicular and causes strange  results
		if (FVector::DotProduct(playerToTargetVec, playerForwardVec) > 0.1)
		{
			return true;
		}
		return false;
	}
	return false;
}
6

This is how I do it:

24-10-1
24-10-11143×316 65.7 KB

2 Likes
7

i just use FindLookAtRotation then break the result, if the ABS of the Z is within your vision arc HalfAngle they’re facing it. you could check Y as well if you care about height

8

Thanks guys. There’s a few suggestions here. I’ll go give them all a try.

9

(post deleted by author)

10

This worked, thank you.

1 Like