Vector3.Lerp

Description

Linearly interpolates between two points.

Interpolates between the points a and b by the interpolant t. The parameter t is clamped to the range [0, 1]. This is most commonly used to find a point some fraction of the way along a line between two endpoints (e.g. to move an object gradually between those points).

The value returned equals (b - a) * t. When t = 0 returns a. When t = 1 returns b. When t = 0.5 returns the point midway between a and b.

using UnityEngine;
using System.Collections;

public class ExampleClass : MonoBehaviour
{
    // Transforms to act as start and end markers for the journey.
    public Transform startMarker;
    public Transform endMarker;

    // Movement speed in units per second.
    public float speed = 1.0F;

    // Time when the movement started.
    private float startTime;

    // Total distance between the markers.
    private float journeyLength;

    void Start()
    {
        // Keep a note of the time the movement started.
        startTime = Time.time;

        // Calculate the journey length.
        journeyLength = Vector3.Distance(startMarker.position, endMarker.position);
    }

    // Move to the target end position.
    void Update()
    {
        // Distance moved equals elapsed time times speed..
        float distCovered = (Time.time - startTime) * speed;

        // Fraction of journey completed equals current distance divided by total distance.
        float fractionOfJourney = distCovered / journeyLength;

        // Set our position as a fraction of the distance between the markers.
        transform.position = Vector3.Lerp(startMarker.position, endMarker.position, fractionOfJourney);
    }
}

See Also: Slerp, LerpUnclamped.