He also wrote a book on PERSPECTIVE that included a general treatment of VANISHINGPOINTS.
他还写出了一部关于透视的著作，其中包括对没影点的一般处理。
2
If two vanishingpoints are not available, focal length cannot be estimated automatically and must be entered manually before the lens model can be solved.
如果两个消失点并不可用，焦距不能估计自动和手动输入必须在透镜模型可以解决。
3
When shooting grids, the camera should be placed an Angle that is not perpendicular to the grid pattern, so the captured image contains two definite vanishingpoints.