Research On The Modeling And Collision Detection In Virtual Hand Based On Component Technology

The term 'Virtual Reality' (VR) was initially coined by Jaron Lanier,founder of VPL Research. As the technology of virtual reality evolves,Virtual Reality has been used in a variety of ways. It is assumed that VR willreshape the interface between people and information technology by offeringnew ways for the communication of information, the visualization ofprocesses, and the creative expression of ideas. The applications of VRinclude training in a variety of domains (military, medical, equipmentoperation, etc.), designing and evaluating (virtual prototyping), architecturalwalk-through, human factors and ergonomic studies, assistance for thehandicapped, entertainment, and so on. Hand is the very important part of the body for the people's daily lifeand works. So the research and analysis of the models of the hand not only isthe hotspot of the HCI, but also develops along with the development of the 3Dimension VR Systems. The virtual hand will be the main means to operateinstead of the mouse. In the virtual condition, the accurate and rapid collisiondetection is the important foundation of the virtual hand emulation, mainlyincluding the model's constitute, the model's motorial renovation, thecollision detection between objects and so on.As is changeable in shape, the virtual hand is different from otherchangeable objects such as cloth, and it has different characters. From theaspect of fingers part, its movement is ragid, namely draw-movement orcircumrotate-movement. So establishing a favorable hand model is veryimportant for the collision detection of virtual hand. However, the moresmooth the model is , the more pieces of surface it includes, and it may bethousands of surfaces, so in the procedure of updating model and collisiondetection, the alternate speed requirement needs to be very strict. It broughtforward a big challenge to the VR. Then we import a concept of'Component', which is definited as compound object that is of imformationsof substrate object's properties and hiberarchy. It can put up collisiondetection as a whole object independently. A component may include severalaccessory objects, and may also be an object itselfe. The key of the virtualcomponent techniques is to establish component rapidly and reduce the timesof collision.The collision detection algorithm based on the hierarchical boundingvolume tree was approved to be the most effective method to solve the ragidbody collision which was used widely. There are variety of bounding trees,such as spheres tree , axis-aligned bounding boxes (AABBs) tree ,object–oriented bounding boxes(OBB) tree , and discrete–oriente dpolytopes(K-Dop)tree, QuOSPOTree, ConvexPieceTree. From the aspect ofcompactness and speed of intersect test, the collision dectetion algorithmbased on the OBB tree is the best way for the close distance collision of rigidobject.For the hand model, such a complex model with multiplex changeablecharacters, the classic OBB tree model based on the elementary is approvedto be so limited on the motivation updating and collision detection. So afteranalysing and studying the algorithm based on hiberarchy bounding boxes,we put forward a method to building a comples object's OBB hiberarchy treebased on the component, and we applied it to modeling the virtual hand. Inthe virtual condition, when we test N objects which are collided or not,commonly we go along the test with each two objects, but in the case of therelative position between parts of objects or the two objects is fixed up, or itaccord with a certain restrict condition, it needn't go along the detection testto the objects every time, so we import the component model, just constructthese objects as a whole component, and go along the detection with thecomponent. This will reduce the time of detection greatly, and improve theefficiency accordingly.The method of constructing OBB hierarchy bounding model based oncomponents shows the great advantage in constructing hierarchy boundingtree of complex objects. The model built in this way is of several strongpointssuch as building hierarchy clearly, updating motion simply, being able toprecede self-collision detecting. In this thesis we mostly research theconstructing and updating method of the component hierarchy tree based onthe OBB, and put forward the method of calculating OBB quickly andbuilding the hierarchy structure of N objects based on the componentbounding box, completing the conformity of N objects, and building thewhole component model. In this paper we disport a hand model to 16 sects,each sect is a cell, it can build a model to the cell, and then we build thecomponent with these models, join these 16 cells as a whole object, and goalong the collision detection with the whole object. Then we specify theupdating method of this cell model. In the end we recite the main method ofupdating hand model and the detailed process. After that we test thesealgorithms by experiments. The results show that it works well in solving theproblems of updating and detecting collision of virtual hand model. We try toapply this method to the flexible and soft objects. We hope the resultsresearched in this thesis can promote wider, more profound research in thisaspect, and wish it help the development of the corresponding technique infuture.