Unity Vector3.Reflect reflection line usage and calculation principle (light hits the plane and reflects)

Calculate the reflection vector of the vector projected onto the object 

Collision simulation:

public class test3 : MonoBehaviour
{
    Vector3 dir;
    Vector3 pos;
    private void Start()
    {
        dir = transform.right;
        pos = transform.position;
    }

    private void Update()
    {
        transform.position += dir * Time.deltaTime*4;
    }
    
    private void OnCollisionEnter2D(Collision2D collision)
    {        
        Vector2 inDirection = (transform.position - pos).normalized;
        Vector2 inNormal = collision.contacts[0].normal;
        dir = Vector2.Reflect(inDirection, inNormal);
        pos = transform.position;
    }
}

Ray Simulation:

Red line: inDirection
Green line: inNormal normal
Blue line: Result reflection line

 

public Transform tsTarget;//目标点
void OnDrawGizmos()
{
#if UNITY_EDITOR
    Color prevColor = Gizmos.color;

    //红线的方向
    Vector3 dir = tsTarget.position - transform.position;

    //从原点向终点打出一条红色的射线
    Gizmos.color = Color.red;
    RaycastHit2D hitInfo = Physics2D.Raycast(transform.position, dir, Mathf.Infinity);
    Gizmos.DrawLine(transform.position, hitInfo.point);//画红线

    //射线碰到碰撞物的法线
    Gizmos.color = Color.green;
    var normal = hitInfo.point + hitInfo.normal;//法线0,0点为基准，所以这里要加上碰撞点的位置
    Gizmos.DrawLine(hitInfo.point, normal);//画绿线

    Gizmos.color = Color.blue;
    Vector2 direction = (Vector2)hitInfo.point + Vector2.Reflect((Vector2)dir, (normal - hitInfo.point));//Vector2.Reflect求反射，但是会出现偏移，经过我反复验证得出的结果
    Gizmos.DrawLine(hitInfo.point, direction);//画蓝线

    Gizmos.color = prevColor;

#endif
}