RaycastHit.distance

Description

从射线原点到撞击点的距离。

对于射线，该距离表示从射线原点到撞击点的矢量大小。

对于扫描的体积或球体投射，该距离表示从原点到体积与其他碰撞体接触处的平移点的矢量大小。

请注意，RaycastHit.point 表示空间中发生碰撞的点。

using UnityEngine;
using System.Collections;

public class ExampleClass : MonoBehaviour {
    public float moveForce = 1.0F;
    public float rotateTorque = 1.0F;
    public float hoverHeight = 4.0F;
    public float hoverForce = 5.0F;
    public float hoverDamp = 0.5F;
    public Rigidbody rb;
    void Start() {
        rb = GetComponent<Rigidbody>();
        rb.drag = 0.5F;
        rb.angularDrag = 0.5F;
    }
    void FixedUpdate() {
        rb.AddForce(Input.GetAxis("Vertical") * moveForce * transform.forward);
        rb.AddTorque(Input.GetAxis("Horizontal") * rotateTorque * Vector3.up);
        RaycastHit hit;
        Ray downRay = new Ray(transform.position, -Vector3.up);
        if (Physics.Raycast(downRay, out hit)) {
            float hoverError = hoverHeight - hit.distance;
            if (hoverError > 0) {
                float upwardSpeed = rb.velocity.y;
                float lift = hoverError * hoverForce - upwardSpeed * hoverDamp;
                rb.AddForce(lift * Vector3.up);
            }
        }
    }
}

另请参阅：Physics.Raycast、Physics.Linecast、Physics.RaycastAll。