Research And Application On Redirected Walking Method In Virtual Reality

With the rapid development of computer hardware,Virtual Reality（VR）technology has become one of the research hotspots.By generating realistic virtual pictures and providing users with multisensory information simulation including vision,auditory and haptics,VR technology allows users to immerse themselves in the virtual scene.Therefore,how to support a more natural roaming in the virtual space,has become a key research issue in the field of VR technology.Although many existing studies have proved that real walking can significantly enhance user experience in virtual roaming,exploring a large virtual space by real walking in a small physical space is still a research problem.To address this issue,the redirected walking（RDW）technology have been proposed to allow users to real walk in large virtual spaces.By using the redirection gains,RDW technology injects subtle deviations between user’s virtual and real movements to imperceptibly manipulate user’s motions.Among the redirection gains,the curvature gain enables the user to unconsciously move along a curved path in the physical space while perceiving to walk straight in the virtual space.Therefore,it is important to explore the user’s sensitivity to the curving of path and study the detection threshold of curvature gain.Based on the characteristics of perception threshold,the RDW method can allow users to real walk in large virtual space without causing users’ awareness.However,how to improve the optimization of the RDW method to reduce the collisions between users and the physical space boundary,and how to increase the applicability of the RDW method to allow users to roam various types of virtual spaces are key research problems in the field of RDW.Based on the above-mentioned research problems,to improve the user experience during virtual roaming,this thesis mainly focuses on the use of RDW to roam a large virtual space.The main research contents in this thesis are outlined as follows:（1）Considering that the length of the virtual path could influence the user’s sensitivity to the curvature gain,we adopt a new psychophysical method to evaluate the detection threshold of curvature gain under different path conditions.The results show that the users are more sensitive to the right-curved real path when walking along a single path.In the condition of two connected paths,the existing of preorder path can significantly increase the sensitivity to the curving of postorder path.In addition,the results further prove that a moderation effect exists on the directional consistency of the preoder path and the postorder path.Specifically,the user’s sensitivity to the postorder path gradually reduces with the increase of preorder path’s curvature gain when the curved directions of both paths are the same.However,when the directions of both paths diverge,the preorder path’s curvature gain has no significant effect on the detection thresholds.（2）To optimize the roaming of virtual spaces without internal obstacles,we propose a redirection mapping algorithm based on polygon skeleton path graph to allows users to walk along a mapped path graph in a small physical space with the guidance of the virtual path graph in the virtual space.First,our algorithm automatically generates the corresponding skeleton path graph of the virtual space by inputting the floor plan of the virtual space.Then,the virtual skeleton path graph is mapped to the physical space based on the physical boundary constraint and the curvature gain criterion.Finally,we adopt a path extension method to increase the robustness and usability of the algorithm.Because the mapping procedure does not apply the reset technique of RDW,our algorithm can ensure the continuity of the roaming experience.Compared with prevalent RDW methods,our algorithm can increase the roaming efficiency,and has a good performance in reducing the user perception distortion and improving the user experience.（3）To address the difficulty of path mapping for complex virtual space and the issue of high path-curving of the mapping result,we propose a segmented redirection mapping method based on virtual path graph with loops to enable the mapping of a virtual path graph with loop structures to the physical space and obtain the corresponding real path graph.Our algorithm automatically generates the path graph with loops for the virtual space,and provides interactive modification to improve the flexibility.In the mapping procedure,we adopt a divide-and-conquer strategy to split the virtual path graph and realize piecewise mapping,and introduce the "virtual edges" to maintain the continuity of path graph after mapping.Based on the dynamic programming strategy,our algorithm adopts the reset and curvature gain of RDW as the optimization and constraint conditions,to significantly reduce the total curving of the mapped path graph while minimizing the number of reset point.The results of mapping validation show that our algorithm is general and flexible for virtual spaces with different sizes and shapes.By comparing to prevalent RDW methods,our algorithm can significantly improve the roaming effectiveness,reduce the collision with physical boundaries,and decrease the perceived distortion during virtual roaming.（4）We design a roaming and interaction paradigm based on redirection mapping,and construct the corresponding VR system prototype.By applying the proposed redirection mapping algorithm,our system allows users to roam different virtual spaces by RDW,and we further explore the interaction mode that combines several interaction approaches during the virtual roaming.By performing user study,we verify and evaluate the proposed system under two practical scenarios including a virtual museum roaming and a school panoramic video exploration.In this thesis,we conduct specific research on the perceptual characteristics and algorithm design of RDW,and apply the research results in practice by constructing a roaming and interactive system,which provides supports for the theory and technology of RDW.