CODEWITHSUNDEEP
c#unity-game-engine
hyperbeecore
hyperbeecore

Reputation: 49

How should I calculate the speed of a Lerp?

I have a Vector2 Lerp statement:

Vector2.Lerp(spawnPos, target, position);

The position variable is a number between 0 and 1, and for all intents and purposes, it increments over time. Think of the way I'm tracking position as a "playhead," like in music or animation, where a cursor moves from left to right as the playback continues.

I want the object to continue moving after it reaches its target, at the same EXACT speed, just infinitely in a direction. I've tried to change the target to the direction multiplied by the distance between the spawn point, but I still can't figure out how to get the correct speed.

Upvotes: 1

Views: 1583

Answers (2)

Salvatore Ambulando
Salvatore Ambulando

Reputation: 422

A slightly easier answer for you: Instead of using Vector2.Lerp and calculating everything, just use Vector2.LerpUnclamped and throw in any value of t you want!

Upvotes: 1

hyperbeecore
hyperbeecore

Reputation: 49

Thanks to Llama's comment, I was able to calculate the speed of a Lerp.

First, record the start and end time of the interpolation, and whether or not the interpolation has completed (position >= 1). Then, if it hasn't finished, lerp as normal. If it HAS finished, note the end time, calculate the speed and direction in which to move, and increment Transform.position by that value.

bool finished = false;

// Since I'm using AudioSettings.dspTime, I need to use double.
// Most forms of telling time in Unity will use float
double startTime;
double endTime;

void Start()
{
    // This is what I am using for my game, 
    // but you can use any way of telling time that Unity/C# provides.
    startTime = AudioSettings.dspTime;
}

void Update()
{
    if(!finished)
    {
        // interpolate
        transform.position = Vector2.Lerp(spawnPos, targetPos, position);
        if(position >= 1)
        {
            // Record our end time
            endTime = AudioSettings.dspTime;
            finished = true
        }
    } else {
        // How long it took to lerp
        double lerpTime = endTime - startTime;
        // How far we lerped
        float distance = Vector2.Distance(spawnPos, targetPos);
        // The speed to further move
        float speed = distance / (float)lerpTime;
        // The direction in which to move
        Vector2 direction = (targetPos - spawnPos).normalized;

        // Continue moving
        transform.position += (Vector3)direction * speed * Time.deltaTime;
    }
}

Upvotes: 1

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