Virtual Three-dimensional Environment, Mouse Operation And Realization

First, I discuss the mouse-pick algorithm in OpenGL and find out the meaning of data in the buffer. I will analysis why OpenGL store the data in an unnormal way.Second, I will raise a mouse-picking algorithm based on OpenGL. It reduces the complex of the intersection judgement between a point and a 3D object from three-dimension to one-dimension. This algorithm creats a 3D cursor in virtual environment, it can move around freely in 3D space. Comparied with the traditional 2D cursor, the 3D cursor can move at right angles to the screen and reflect the perspective projection naturely. The algorithm will judge whether the hot point of 3D cursor in the space of the target object, and set the object to be picked state if the hot point in the space of the object.I also design an experiment to test the error. And I balance the precision and facility of the algorithm when it is applied to user interface. The error has a relationship with mouse step, the nice step make the cursor move slowly, and the large step make the cursor penetrate the object which,however ,will not be recongined as picked up. At last, the algorithm is improved to meet this situation.The paper also discusses the operation of the 3D cursor. User can move the mouse, press/unpress the right/left button and rotate the wheel to control the 3D cursor. It provids three feedback states, pointed, atteched, and selected to user.A 3D virtual environment is developed to apply this mouse-picking algorithm. It contains scene and object. The paper discusses how to design the scene; it includes the attributes, operations and rendering. The paper also explains that why the object should regist to the scene and how. There are three ways to assign name id to each object in a scene, and I will analyses which is the best one. The door model is designed to trigger the switch between different scenes. Computer model is designed to launch the applications. Camera is designed to roam in the virtual environment. And the 3D popup menu is designed to apply several commands to one object.