[Solved]How can I compare the distance between NPC and player

Development Programming & Scripting
1

How can I find the distance between the player and another player or bot?

What I have so far I think is on the right path but is not working properly.

	AShooterBot* MyBot = Cast(GetPawn());

// this is the line in question 
	float playerDistance = VectorMax( MyBot.Location - Enemy.Location );

any help would be great as I am also not even sure if I am using the right vector

thanks

2

I’m going to give you the answer but I’m also going to explain why it’s the answer. And you’re definitely on the right track!

When you do something like MyBot.Location - Enemy.Location then that results in a new vector between those two points: MyBot.Location and Enemy.Location.

So, we already know we’re going to want this:

FVector vector_between_locations = MyBot.Location - Enemy.Location;

So now we have our vector that points from one location to the other. You want the distance. Well, in that case we want to get the size of the vector:

float distance_between_locations = vector_between_locations.Size();

And there’s your answer!

3

I agree with Neil!

If you want to use easy static FORCEINLINE functions for this you can use FVector::Dist() and FVector::DistSquared()

But Neil is definitely explaining to you more of how it all actually works :slight_smile:

/**
	 * Euclidean distance between two points.
	 *
	 * @param V1 The first point.
	 * @param V2 The second point.
	 *
	 * @return The distance between two points.
	 */
	static FORCEINLINE float Dist( const FVector &V1, const FVector &V2 );

	/**
	 * Squared distance between two points.
	 *
	 * @param V1 The first point.
	 * @param V2 The second point.
	 *
	 * @return The squared distance between two points.
	 */
	static FORCEINLINE float DistSquared( const FVector &V1, const FVector &V2 );
1 Like
4

Ok so if I understand this right and Rama thank you for helping out also.
I would need to add another variable and structure it like this?

FVector playerDistance = MyBot.Location - Enemy.Location;

float MyDistanceFrom = playerDistance.Size();
5

I believe you can also get by without adding another variable as follows :

float MyDistanceFrom = (MyBot.Location - Enemy.Location).Size();

The key point to note is that (MyBot.Location - Enemy.Location) is a FVector, which is because each of the MyBot.Location and Enemy.Location are FVector. So their difference is an FVector as well. Now when you call FVector::Size() on an object of FVector as follows (MyBot.Location - Enemy.Location).Size(), what you get is a float quantity which represents the length of that FVector.

6

ok I see now to find the dereference for Location.

7

Just know that FVector::Size() takes a square root, which traditionally is slow. A good rule of thumb is to use FVector::SizeSquared() and compare those values unless you absolutely need to know the real distance.

You can always do the following for readability.

if (DistVector.SizeSquared <= (MyDist * MyDist))

And that is typically faster than the Size() itself.

8

An example of usage: if (FVector::DistSquared(PlayerLocation, PreviousPlayerLocation) > 10) {