详解unity中tranform.worldToLocalMatrix

本来是想写一个求A物体在B物体坐标系下的坐标。

写完了才发现有worldToLocalMatrix这个函数，后来查了查还有InverseTransformPoint这个函数。。。

没看API就直接写真血亏。

算了，就当是一次详解吧，直接上代码。
 

  Vector3 world2Local(Transform _worldPosition) {
        Matrix4x4 trans = new Matrix4x4(
          new Vector4(1, 0, 0, 0),
          new Vector4(0, 1, 0, 0),
          new Vector4(0, 0, 1, 0),
          new Vector4(-transform.position.x, -transform.position.y, -transform.position.z, 1));

        Matrix4x4 rotZ = new Matrix4x4(
            new Vector4(Mathf.Cos(-transform.eulerAngles.z * Mathf.PI / 180), Mathf.Sin(-transform.eulerAngles.z * Mathf.PI / 180), 0, 0),
            new Vector4(-Mathf.Sin(-transform.eulerAngles.z * Mathf.PI / 180), Mathf.Cos(-transform.eulerAngles.z * Mathf.PI / 180), 0, 0),
            new Vector4(0, 0, 1, 0),
            new Vector4(0, 0, 0, 1));

        Matrix4x4 rotX = new Matrix4x4(
            new Vector4(1, 0, 0, 0),
            new Vector4(0, Mathf.Cos(-transform.eulerAngles.x * Mathf.PI / 180), Mathf.Sin(-transform.eulerAngles.x * Mathf.PI / 180), 0),
            new Vector4(0, -Mathf.Sin(-transform.eulerAngles.x * Mathf.PI / 180), Mathf.Cos(-transform.eulerAngles.x * Mathf.PI / 180), 0),
            new Vector4(0, 0, 0, 1));

        Matrix4x4 rotY = new Matrix4x4(
               new Vector4(Mathf.Cos(-transform.eulerAngles.y * Mathf.PI / 180), 0, -Mathf.Sin(-transform.eulerAngles.y * Mathf.PI / 180), 0),
               new Vector4(0, 1, 0, 0),
               new Vector4(Mathf.Sin(-transform.eulerAngles.y * Mathf.PI / 180), 0, Mathf.Cos(-transform.eulerAngles.y * Mathf.PI / 180), 0),
               new Vector4(0, 0, 0, 1));

        Matrix4x4 Mview = (new Matrix4x4(
            new Vector4(1, 0, 0, 0),
            new Vector4(0, 1, 0, 0),
            new Vector4(0, 0, 1, 0),
            new Vector4(0, 0, 0, 1)
            )) * rotZ * rotX * rotY * trans;

        Vector4 Pworld = new Vector4(_worldPosition.position.x, _worldPosition.position.y, _worldPosition.position.z, 1);

        Vector3 PLocal = Mview * Pworld;
        //Vector4 Pcamera = transform.worldToLocalMatrix * Pworld;
        Debug.Log(PLocal);

        return PLocal;
    }

就这样吧，注意Mview中rotZ*rotX*rotY*trans，

因为平常是先旋转再平移，所以这里要先平移再旋转，并且平常是先转z再转x再转y，所以这里是先y再x再z，详情请看unity shader 入门精要第67 和第76页。