Vector3.MoveTowards

Parameters

Returns

Vector3 新位置。

Description

Calculate a position between the points specified by current and target, moving no farther than the distance specified by maxDistanceDelta.

Use the MoveTowards member to move an object at the current position toward the target position. By updating an object’s position each frame using the position calculated by this function, you can move it towards the target smoothly. Control the speed of movement with the maxDistanceDelta parameter. If the current position is already closer to the target than maxDistanceDelta, the value returned is equal to target; the new position does not overshoot target. To make sure that object speed is independent of frame rate, multiply the maxDistanceDelta value by Time.deltaTime (or Time.fixedDeltaTime in a FixedUpdate loop).

Note that if you set maxDistanceDelta to a negative value, this function returns a position in the opposite direction from the target.

using UnityEngine;
using System.Collections;

// Vector3.MoveTowards example.

// A cube can be moved around the world. It is kept inside a 1 unit by 1 unit
// xz space. A small, long cylinder is created and positioned away from the center of
// the 1x1 unit. The cylinder is moved between two locations. Each time the cylinder is
// positioned the cube moves towards it. When the cube reaches the cylinder the cylinder
// is re-positioned to the other location. The cube then changes direction and moves
// towards the cylinder again.
//
// A floor object is created for you.
//
// To view this example, create a new 3d Project and create a Cube placed at
// the origin. Create Example.cs and change the script code to that shown below.
// Save the script and add to the Cube.
//
// Now run the example.

public class Example : MonoBehaviour
{
    // Adjust the speed for the application.
    public float speed = 1.0f;

    // The target (cylinder) position.
    private Transform target;

    void Awake()
    {
        // Position the cube at the origin.
        transform.position = new Vector3(0.0f, 0.0f, 0.0f);

        // Create and position the cylinder. Reduce the size.
        GameObject cylinder = GameObject.CreatePrimitive(PrimitiveType.Cylinder);
        Camera.main.transform.position = new Vector3(0.85f, 1.0f, -3.0f);

        // Grab cylinder values and place on the target.
        target = cylinder.transform;
        target.transform.localScale = new Vector3(0.15f, 1.0f, 0.15f);
        target.transform.position = new Vector3(0.8f, 0.0f, 0.8f);

        // Position the camera.
        Camera.main.transform.position = new Vector3(0.85f, 1.0f, -3.0f);
        Camera.main.transform.localEulerAngles = new Vector3(15.0f, -20.0f, -0.5f);

        // Create and position the floor.
        GameObject floor = GameObject.CreatePrimitive(PrimitiveType.Plane);
        floor.transform.position = new Vector3(0.0f, -1.0f, 0.0f);
    }

    void Update()
    {
        // Move our position a step closer to the target.
        float step =  speed * Time.deltaTime; // calculate distance to move
        transform.position = Vector3.MoveTowards(transform.position, target.position, step);

        // Check if the position of the cube and sphere are approximately equal.
        if (Vector3.Distance(transform.position, target.position) < 0.001f)
        {
            // Swap the position of the cylinder.
            target.position *= -1.0f;
        }
    }
}