judge the position of an actor relative to the player pawn

Development Programming & Scripting C++
1

I was wandering how to judge if an actor is on the left or on the right of the player?

2

The dot product is your friend, the following should work for any kind of actor not just players. Untested and uncompiled.


/**
 * return true if Direction is left of Rotation
 * NOTE: Direction does NOT have to be normalized
 */
bool IsLeftOrRight(FRotator Rotation, FVector Direction)
{
	FVector RightVector = FRotationMatrix(Rotation).GetScaledAxis(EAxis::Y);

	//TODO: handle == 0.0f: neither left or right but either directly in front or behind; will also be == 0.0f if Direction is == FVector::ZeroVector (RightVector should always be normalize because of FRotationMatrix)
	//this is the dot product (operator|)
	return (RightVector | Direction) < 0.0f;
}

/**
 * return true if OtherLocation is left of Location/Rotation
 */
bool IsLeftOrRight(FVector Location, FRotator Rotation, FVector OtherLocation)
{
	FVector LocationToOtherLocation = OtherLocation - Location;

	return IsLeftOrRight(Rotation, LocationToOtherLocation);
}

bool IsLeftOrRight(AActor* Player, AActor* Other)
{
	//TODO: check Player and Other != nullptr
	return IsLeftOrRight(Player->GetActorLocation(), Player->GetActorRotation(), Other->GetActorLocation());
}