This is faster, but viewdirection is not entirely correct when camera gets close to surface.
这样更快，但是当摄像机接近表面的时候，视图方向不完全正确。
2
The System sets different view points and viewdirection for the convenient of the operator to get information from more orients according to real need.
根据实际需要，集装箱装卸视景系统设置了不同视点位置和视线方向，为操作者提供多方位的信息。
3
What this tool does it take only the very first sample in the selection range and the very last sample in the range, and then linearly interpolates the viewdirection smoothly across the entire range.