Diary During Summer Vacation 9

Today I found a bug in the code that is dealing with the 4 view implementation. When doing 2D mouse position to 3D world position unprojection in a view, the code accidentally always takes the perspective camera's view matrix, and hence leads to a wrong unprojection result in other three views. It makes the unprojected 3D points unpredictably goes anywhere. This problem has now been fixed.