pl.net 的轨迹（线性渲染器）不反映实际运动 Unity 3d

Question

I'm trying to recreate a solar system and i'm using newton's law. The actual force works great but when i try to "predict" the path of a pl.net it just doesn't work: to predict it i use a lineRenderer whose points get placed on the position at the Tth instant ( T being time ). When i start the game they are close but as time passes the pl.net actually goes in "orbit" while the line shoots up. I can't understand why this happens seen that i calculate the pl.net's position in the same way as the line's one. I also tried instantiating a ball but same result.

public void UpdateSpeed(Vector3 acceleration,float time)
{
    velocity += acceleration * time;
}

public void UpdatePosition(float time)
{
    transform.position +=velocity *time;
}

public void UpdateLine(float time)
{
    position += velocity * time;
    Debug.Log(position);
    Instantiate(ball, position, Quaternion.identity);
    line.positionCount++;
    line.SetPosition(line.positionCount-1, position);
}

and here the function that computes acceleration

 public Vector3 CalculateAcceleration(GameObject subj, float time)
{
    Vector3 Acceleration = Vector3.zero;
    foreach (var pl in planets)
    {
        if (pl != subj)
        {
            float sqrDistance= Mathf.Pow(Vector3.Distance(subj.transform.position, pl.transform.position), 2);
            Vector3 direction = (pl.transform.position - subj.transform.position).normalized;
            Acceleration += direction * (pl.GetComponent<Rigidbody>().mass * GravitationalConstant)/sqrDistance;
        }
    }
    return Acceleration;
}

is the rigidbody attached to the pl.net making a difference for the position?

Answer 1

If you are having trouble with the orbit, calculate the OrbitFirst then call it to move your object with different time, just modify delta time below

LineRenderer lr; 

//Build the orbit path/line
void CalculateOrbitEllipse()
{
    Vector3[] points = new Vector3[segments + 1];
    for (int i = 0; i < segments; i++)
    {
        Vector2 position2D = orbitPath.Evaluate((float)i / (float)segments);
        points[i] = new Vector3(position2D.x, 0f, position2D.y);
    }
    points[segments] = points[0];

    lr.positionCount = segments + 1;
    lr.SetPositions(points);
}


//make the planet move, 
//you can invoke this using your time variable, Time.deltaTime see below
IEnumerator AnimationOrbit()
{
    if (orbitPeriod < 0.1f)
    {
        orbitPeriod = 0.1f;
    }
    float orbitSpeed = 0.1f / orbitPeriod;
    while (orbitActive)
    {
        orbitProgress += Time.deltaTime * orbitSpeed;
        orbitProgress %= 1f;
        SetOrbitingObjectPosition();
        lr = GetComponent<LineRenderer>();
        CalculateOrbitEllipse();
        yield return null;
    }
 }


 void SetOrbitingObjectPosition()
 {
    Vector2 orbitPos = orbitPath.Evaluate(orbitProgress);
    orbitingObject.localPosition = new Vector3(orbitPos.x, 0, orbitPos.y);        
 }

Answer 2

so as often happens i'm an idiot. I was calculating in the acceleration function distances with the actual bodies positions instead of the simulated position so i always had a false value that was increasing instead of varying