预测刚体对象在x秒内的位置 [英] Predict the position of a Rigidbody Object in x second

问题描述

假设您有一个移动的Rigidbody对象.力通过Rigidbody.AddForce或Rigidbody.velocity施加到该对象.该对象可以滚动碰到另一个对象并改变方向.

Let's say that you have a Rigidbody Object that moves. Force is added to this Object via Rigidbody.AddForce or Rigidbody.velocity. The Object can roll hit another Object and change direction.

我了解外推，但是在这种情况下，几乎不可能使用某些公式来在 x 秒内获得对象的位置，因为对象可以撞击另一个对象并在此过程中更改速度/方向.

I know about Extrapolation but in this case, it's nearly impossible to use some formula to obtain the position of the object in x seconds, since the Object can hit another object and change speed/direction in the process.

Unity 2017引入了 Physics.autoSimulation 和 Physics.Simulate 解决此问题.对于2D物理，即 Physics2D.autoSimulation 和 Physics2D.Simulate .我所做的只是首先将Physics.autoSimulation设置为false，然后调用Physics.Simulate函数.

Unity 2017 introduced Physics.autoSimulation and Physics.Simulate to solve this problem. For 2D physics, that is Physics2D.autoSimulation and Physics2D.Simulate. All I did was first set Physics.autoSimulation to false then call the Physics.Simulate function.

在我的示例中，我想知道在加力后4秒内Rigidbody的位置，它似乎可以像1那样在几秒钟内正常工作.问题是，当我向Simulate函数传递诸如5及更高版本的较大数字时，预测位置不是准确的.还很遥远

In my example, I wanted to know where a Rigidbody would be in 4 seconds after adding force to it, it seems to work fine for tiny seconds like 1. The problem is that when I pass in bigger numbers like 5 and above, to the Simulate function, the predicted position is not accurate. It's way way off.

为什么会发生这种情况，我该如何解决?这个问题在Android设备上更严重.

Why is this happening and how can I fix it? This problem is worse on Android devices.

我当前的Unity版本是 Unity 2017.2.0b5 .

My current Unity version is Unity 2017.2.0b5.

以下是我正在使用的示例代码. guide GameObject仅用于显示/显示该预测位置.

Below is the sample code I am using. The guide GameObject is simply used to display/show where that predicted position is.

public GameObject bulletPrefab;
public float forceSpeed = 50;

public GameObject guide;

// Use this for initialization
IEnumerator Start()
{
    //Disable Physics AutoSimulation
    Physics.autoSimulation = false;

    //Wait for game to start in the editor before moving on(NOT NECESSARY)
    yield return new WaitForSeconds(1);

    //Instantiate Bullet
    GameObject obj = Instantiate(bulletPrefab);

    Rigidbody bulletRigidbody = obj.GetComponent<Rigidbody>();

    //Calcuate force speed. (Shoot towards the x + axis)
    Vector3 tempForce = bulletRigidbody.transform.right;
    tempForce.y += 0.4f;
    Vector3 force = tempForce * forceSpeed;

    //Addforce to the Bullet
    bulletRigidbody.AddForce(force, ForceMode.Impulse);

    //yield break;
    //Predict where the Rigidbody will be in 4 seconds
    Vector3 futurePos = predictRigidBodyPosInTime(bulletRigidbody, 4f);//1.3f
    //Show us where that would be
    guide.transform.position = futurePos;
}

Vector3 predictRigidBodyPosInTime(Rigidbody sourceRigidbody, float timeInSec)
{
    //Get current Position
    Vector3 defaultPos = sourceRigidbody.position;

    Debug.Log("Predicting Future Pos from::: x " + defaultPos.x + " y:"
        + defaultPos.y + " z:" + defaultPos.z);

    //Simulate where it will be in x seconds
    Physics.Simulate(timeInSec);

    //Get future position
    Vector3 futurePos = sourceRigidbody.position;

    Debug.Log("DONE Predicting Future Pos::: x " + futurePos.x + " y:"
        + futurePos.y + " z:" + futurePos.z);

    //Re-enable Physics AutoSimulation and Reset position
    Physics.autoSimulation = true;
    sourceRigidbody.velocity = Vector3.zero;
    sourceRigidbody.useGravity = false;
    sourceRigidbody.position = defaultPos;

    return futurePos;
}

推荐答案

您甚至很幸运1的值完全起作用.您不应将高于0.03的任何值传递给Physics.Simulate或Physics2D.Simulate函数.

You are even lucky that the value of 1 worked at-all. You shouldn't pass any value above 0.03 to the Physics.Simulate or Physics2D.Simulate function.

当值大于0.03时，您必须将其分段，然后在循环中使用Simulate函数.减少 x 时间，同时检查它是否仍大于或等于Time.fixedDeltaTime应该可以.

When the value is above 0.03, you have to it into pieces then use the Simulate function in a loop. Decrementing the x time while checking if it is still more or equals to Time.fixedDeltaTime should do it.

替换

Physics.Simulate(timeInSec);

使用

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

您新的完整的predictRigidBodyPosInTime函数应如下所示:

Your new complete predictRigidBodyPosInTime function should look something like this:

Vector3 predictRigidBodyPosInTime(Rigidbody sourceRigidbody, float timeInSec)
{
    //Get current Position
    Vector3 defaultPos = sourceRigidbody.position;

    Debug.Log("Predicting Future Pos from::: x " + defaultPos.x + " y:"
        + defaultPos.y + " z:" + defaultPos.z);

    //Simulate where it will be in x seconds
    while (timeInSec >= Time.fixedDeltaTime)
    {
        timeInSec -= Time.fixedDeltaTime;
        Physics.Simulate(Time.fixedDeltaTime);
    }

    //Get future position
    Vector3 futurePos = sourceRigidbody.position;

    Debug.Log("DONE Predicting Future Pos::: x " + futurePos.x + " y:"
        + futurePos.y + " z:" + futurePos.z);

    //Re-enable Physics AutoSimulation and Reset position
    Physics.autoSimulation = true;
    sourceRigidbody.velocity = Vector3.zero;
    sourceRigidbody.useGravity = false;
    sourceRigidbody.position = defaultPos;

    return futurePos;
}

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