A物体在NGUI空间，父节点C，B物体在Unity3d空间。AC的渲染相机为camera2d，B的渲染相机为camera3d，如果我们希望把A物体设置在B物体上面10像素的位置上，但是A物体仍旧在NGUI空间，可以如下设置：

Vector3 result = Vector3.zero;

Vector3 screen3dPos = camera3d.WorldToScreenPoint(B.position);

result = camera2d.ScreenToWorldPoint(screen3dPos);

result.z = 0;

result = c.InverseTransformPoint(result);

result.y += 10;

A.localpostion = result;