利用IK调整目标的Unity3D向量数学问题

Question

基本上，我在联合使用Ik系统，我希望我的枪瞄准鼠标。问题是，我只能控制IK骨的位置，这不是子弹的来源，而是一个枪械物体，它是IK骨的一个子物体，它和它一起旋转。我想要做的是以一种方式定位IK，这样FirePoint(子弹就会从这里出来)总是向鼠标旋转。

下面是一个更好地可视化问题的图像

​

Answer 1

评论中的解释

// currentFirePoint and currentIKPoint are the transform of the fire Point and the 
// world position of IK Point at some given moment. 
// aimOrign and mousePosInWorldSpace are world space positions of the aim Origin and 
// mouse position that produce the desired IK point.
Vector3 GetNewIKPoint(Transform currentFirePoint, Vector3 currentIKPoint,
        Vector3 aimOrigin, Vector3 mousePosInWorldSpace)
{
    float firePointRange = aimOriginToCurrentFP.magnitude;

    //Find the local position of IK in Fire Point space
    Vector3 curFirePointToIK = currentIKPoint - currentFirePoint;
    Vector3 localFirePointToIK = currentFirePoint.InverseTransformVector(
            curFirePointToIK);

    // Stuff above this point could be done once and cached, 
    // assuming things like the offset or fire point range don't change.
    
    // Determine where the new fire point will be
    Vector3 newFireDirection = (mousePosInWorldSpace - aimOrigin).normalized;
    Vector3 newFirePoint = firePointRange * newFireDirection;

    // Find rotation such that local right = newFireDirection
    // and local up is closer to Vector3.up than Vector3.down

    // find local forward
    Vector3 newFPLocalForward = Vector3.Cross(newFireDirection, Vector3.up);
    // find local up
    Vector3 newFPLocalUp = Vector3.Cross(newFPLocalForward, newFireDirection);
    Quaternion newFPRotation = Quaternion.LookRotation(newFPLocalForward, 
            newFPLocalUp);

    // Apply that rotation to the local position of IK to find the world space offset. 
    Vector3 newFirePointToIK = newFPRotation * localFirePointToIK;

    // Add to fire point to get world space position
    return newFirePoint + newFirePointToIK;
}

同样的逻辑也适用于三维空间，但也要相应地改变newFPRotation的计算。