Unity模拟万有引力

效果

物体受到标签为RigidBody的一切物体的万有引力，引力满足距离平方反比规律。

用法

施加于被吸引的物体之上，物体需要添加RigidBody组件，物体重量由RigidBody的mass字段决定。万有引力系数在代码中以K表示。

注意

由于Vector3类的枚举字段为float型。float型的指数位为8位，即范围为-2^128~+2128。一旦物体间距离足够小，引力会急剧增大而导致数据溢出，此时的引力会出现不可预料的突变。因此在使用的过程中应该避免距离过近。实际上在现实中，当物体间的万有引力到达如此显著的程度时，其他基本力的影响将更加明显，此时仅模拟万有引力没有意义。

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using UnityEngine;
using System.Collections;

public class BeingAttracted : MonoBehaviour {
    public GameObject[] m_objects;  //另一个物体
    public Vector3 m_speed = new Vector3(0, 0, 0);    //运动速度

    private Vector3 m_attractiveForce;      //二者之间的引力
    private float m_mass;     //这个物体的质量
    private float m_forceCoefficient;     //引力系数 k*M*m

    private const float K = 25.0f;

    // Use this for initialization
    void Start () {
        m_mass = this.GetComponent<Rigidbody>().mass;
        this.GetComponent<Rigidbody>().velocity = m_speed;
    }
    
    // Update is called once per frame
    void Update () {
        m_objects = GameObject.FindGameObjectsWithTag("RigidBody");
        m_attractiveForce = new Vector3(0, 0, 0);
        foreach (GameObject attractingObject in m_objects)
            if(attractingObject != this.gameObject)
                GetAttractiveForce(attractingObject);
        this.GetComponent<Rigidbody>().AddForce(m_attractiveForce);
        //this.GetComponent<Rigidbody>().velocity = m_speed;

    }
    void GetAttractiveForce(GameObject attractingObject){
        Vector3 distanceVector = attractingObject.transform.position - this.transform.position;   //二者间的向量距离
        Vector3 forceDirection = distanceVector.normalized;    //引力方向
        float sqrDistance = distanceVector.sqrMagnitude;
        //if (sqrDistance != 0 && sqrDistance > 2)
        //{
        m_forceCoefficient = K * attractingObject.GetComponent<Rigidbody>().mass * m_mass;
        m_attractiveForce += m_forceCoefficient / sqrDistance * forceDirection;
        //}
        Debug.Log("forceDirection" + forceDirection + ";distance" + distanceVector.sqrMagnitude + ";acceleration" + m_attractiveForce);
    }
}