internal Plane boardPlane;

   private void Start(){//初始化Plane，让它的法线是这个画板的forward向量，并且法线通过画板的中心位置，由此确定一个平面boardPlane = new Plane(transform.forward, transform.position);　　　　　......    }

/// <summary>/// 判断笔尖是在画板的正面还是背面/// </summary>/// <param name="point">笔尖的位置</param>/// <returns>true 在正面;false 在背面</returns>public bool GetSideOfBoardPlane(Vector3 point){return boardPlane.GetSide(point);}/// <summary>/// 笔尖与平面的距离/// </summary>/// <param name="point">笔尖的位置</param>/// <returns>当在正面的时候返回正值，当在背面的时候返回负值</returns>public float GetDistanceFromBoardPlane(Vector3 point){return boardPlane.GetDistanceToPoint(point);}/// <summary>/// 矫正后的笔尖应该在的位置/// </summary>/// <param name="point">笔尖的位置</param>/// <returns>矫正后的笔尖位置</returns>public Vector3 ProjectPointOnBoardPlane(Vector3 point){float d = -Vector3.Dot(boardPlane.normal, point - transform.position);return point + boardPlane.normal * d;}

using VRTK.GrabAttachMechanics;
using UnityEngine;public class PainterGrabAttach : VRTK_BaseGrabAttach
{[Header("Painter Options")][SerializeField]private Transform tips;//笔尖private static Board board;//画板#region 重写的父类方法protected override void Initialise(){//初始化父类的一些字段，这些字段只是标识这个抓附机制的作用tracked = false;kinematic = false;climbable = false;//初始化自定义的属性if (precisionGrab)//最好不要用精确抓取，因为这样很有可能会让笔处于一个不合理的位置，这样使用的时候，会很变扭（比如必须手腕旋转一个角度，笔才是正的）
        {Debug.LogError("PrecisionGrab cant't be true in case of PainterGrabAttach Mechanic");}board = FindObjectOfType<Board>();}public override bool StartGrab(GameObject grabbingObject, GameObject givenGrabbedObject, Rigidbody givenControllerAttachPoint){if (base.StartGrab(grabbingObject, givenGrabbedObject, givenControllerAttachPoint)){SnapObjectToGrabToController(givenGrabbedObject);grabbedObjectScript.IsKinematic = true;return true;}return false;}public override void StopGrab(bool applyGrabbingObjectVelocity){ReleaseObject(applyGrabbingObjectVelocity);base.StopGrab(applyGrabbingObjectVelocity);}public override void ProcessFixedUpdate(){if (grabbedObject)//只有抓住物体后，grabbedObject才不会
        {grabbedObject.transform.rotation = controllerAttachPoint.transform.rotation * Quaternion.Euler(grabbedSnapHandle.transform.localEulerAngles);grabbedObject.transform.position = controllerAttachPoint.transform.position - (grabbedSnapHandle.transform.position - grabbedObject.transform.position);float distance = board.GetDistanceFromBoardPlane(tips.position);//笔尖距离平面的距离bool isPositiveOfBoardPlane = board.GetSideOfBoardPlane(tips.position);//笔尖是不是在笔尖的正面Vector3 direction = grabbedObject.transform.position - tips.position;//笔尖位置指向笔的位置的差向量//当笔尖穿透的时候，需要矫正笔的位置 if (isPositiveOfBoardPlane || distance > 0.0001f){Vector3 pos = board.ProjectPointOnBoardPlane(tips.position);grabbedObject.transform.position = pos - board.boardPlane.normal * 0.001f + direction;//pos是笔尖的位置，而不是笔的位置，加上direction后才是笔的位置
            }}}#endregion//让手柄抓住物体private void SnapObjectToGrabToController(GameObject obj){if (!precisionGrab){SetSnappedObjectPosition(obj);}}//设置物体和手柄连接的位置 private void SetSnappedObjectPosition(GameObject obj){if (grabbedSnapHandle == null){obj.transform.position = controllerAttachPoint.transform.position;}else{//设置旋转,controllerAttachPoint是手柄上的一个与物体的连接点obj.transform.rotation = controllerAttachPoint.transform.rotation * Quaternion.Euler(grabbedSnapHandle.transform.localEulerAngles);//因为grabbedSnapHandle和obj.transform之间可能不是同一个点，所以为了让手柄抓的位置是grabbedSnapHandle,需要减去括号中代表的向量obj.transform.position = controllerAttachPoint.transform.position - (grabbedSnapHandle.transform.position - obj.transform.position);}}}