c# - 如何正确使用 Physics.autoSimulation？

Question

我正在尝试使用 Physics.autoSimulation 预测游戏对象的位置(游戏对象附有刚体)。问题是当我触发模拟时，对象有某种闪烁。像这样:

我读了这个thread .我开始认为我没有正确使用 autoSimulation。这是我的代码:

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class TestBall : MonoBehaviour {


    public float timeCheck = 3f;
    public float force = 10f;

    private Rigidbody rb;

    void Start () {

        rb = GetComponent<Rigidbody>();

    }//end Start



    void Update () {

        if (Input.GetKeyDown(KeyCode.Space)) {

            //Starts the simulation...
            Physics.autoSimulation = false;
            rb.AddForce(Vector3.right * force, ForceMode.Impulse);
            Vector3 futurePosition = CheckPosition(rb);    
            print("Future position at " + futurePosition);

            //...and move the GameObject for real
            rb.AddForce(Vector3.right * force, ForceMode.Impulse);

        }//end if

    }//end Update



    Vector3 CheckPosition (Rigidbody defaultRb) {

        Vector3 defaultPos = defaultRb.position;
        Quaternion defaultRot = defaultRb.rotation;

        float timeInSec = timeCheck;

        while (timeInSec >= Time.fixedDeltaTime) {

            timeInSec -= Time.fixedDeltaTime;
            Physics.Simulate(Time.fixedDeltaTime);

        }//end while

        Vector3 futurePos = defaultRb.position;

        Physics.autoSimulation = true;

        defaultRb.velocity = Vector3.zero;
        defaultRb.position = defaultPos;
        defaultRb.rotation = defaultRot;

        return futurePos;

    }//end CheckPosition

}//end TestBall

就好像有那么一小会儿，游戏对象在模拟结束时移动了，然后又回来了，因为位置在 CheckPosition 函数中重置了。

感谢您的帮助!

Answer 1

您正在正确使用 Physics.autoSimulation。问题在于您如何重置位置。

修改刚体的位置和旋转不同于修改其变换的位置和旋转。您想要使用变换而不是刚体来重置对象的变换，这样移动将立即发生而不是在多个帧上发生，因为这将使它在屏幕上可见。

替换:

defaultRb.position = defaultPos;
defaultRb.rotation = defaultRot;

与

defaultRb.transform.position = defaultPos;
defaultRb.transform.rotation = defaultRot;

---

此外，由于这是一个滚球，设置 velocity 不足以阻止它。您还必须设置它的 angularVelocity，因为球在旋转和平移:

defaultRb.velocity = Vector3.zero;
defaultRb.angularVelocity = Vector3.zero;

这是没有闪烁的新 CheckPosition 函数:

Vector3 CheckPosition(Rigidbody defaultRb)
{

    Vector3 defaultPos = defaultRb.position;
    Quaternion defaultRot = defaultRb.rotation;

    float timeInSec = timeCheck;

    while (timeInSec >= Time.fixedDeltaTime)
    {

        timeInSec -= Time.fixedDeltaTime;
        Physics.Simulate(Time.fixedDeltaTime);

    }//end while

    Vector3 futurePos = defaultRb.position;


    Physics.autoSimulation = true;

    defaultRb.velocity = Vector3.zero;
    defaultRb.angularVelocity = Vector3.zero;

    defaultRb.transform.position = defaultPos;
    defaultRb.transform.rotation = defaultRot;

    return futurePos;

}//end CheckPosition

---

最后，您当前的代码不会在旧的强制之上添加强制。这意味着如果您按下空格键并再次按下，则不会在旧力之上添加力。相反，对象停止，然后添加新的力。旧的丢了。

如果您想在旧力之上添加新力，您必须在模拟前存储当前速度和角速度，然后在模拟后将它们应用回刚体。 物体速度应随时间增加。

这与您的问题无关，只是代码中的另一个错误。下面是对此的修复(新的 Update 和 CheckPosition 函数):

void Update()
{
    if (Input.GetKeyDown(KeyCode.Space))
    {
        //Get current velocity and angularVelocity
        Vector3 defaultVelocity = rb.velocity;
        Vector3 defaultAngularVelocity = rb.angularVelocity;

        //Starts the simulation...
        Physics.autoSimulation = false;
        rb.AddForce(Vector3.right * force, ForceMode.Impulse);
        Vector3 futurePosition = CheckPosition(rb, defaultVelocity, defaultAngularVelocity);
        print("Future position at " + futurePosition);

        //...and move the GameObject for real
        rb.AddForce(Vector3.right * force, ForceMode.Impulse);

    }//end if

}//end Update



Vector3 CheckPosition(Rigidbody defaultRb, Vector3 defaultVelocity, Vector3 defaultAngularVelocity)
{

    Vector3 defaultPos = defaultRb.position;
    Quaternion defaultRot = defaultRb.rotation;

    float timeInSec = timeCheck;

    while (timeInSec >= Time.fixedDeltaTime)
    {
        timeInSec -= Time.fixedDeltaTime;
        Physics.Simulate(Time.fixedDeltaTime);

    }//end while

    Vector3 futurePos = defaultRb.position;


    Physics.autoSimulation = true;

    //Stop object force
    defaultRb.velocity = Vector3.zero;
    defaultRb.angularVelocity = Vector3.zero;

    //Reset Position
    defaultRb.transform.position = defaultPos;
    defaultRb.transform.rotation = defaultRot;

    //Apply old velocity and angularVelocity
    defaultRb.velocity = defaultVelocity;
    defaultRb.angularVelocity = defaultAngularVelocity;

    return futurePos;

}//end CheckPosition