This article focuses on developments and uses of certain 3D computer applications which are aimed at simplifying human-computer interaction by using hand gestures. It describes some developments in the field of computer software to achieve this simplification. The author describes how the 3D application software help in making presentation easier. A few more simulation methods have been described like, the speech recognition algorithms which were believed very useful for certain tasks but it was also found that these cannot be used to input spatial parameters that have to be varied quickly and continuously. One more advanced version of the 3D applications is 3D Virtual Flythru application, which allows the user to fly over a graphically generated terrain. Various ways of finger movements have been described for using the application to perform various tasks. The author describes that over 200 qualitative and quantitative trials and tests performed with users of different age, gender, skin complexion and hand size to estimate the system's accuracy and usability, in using these applications.