Title: Manipulation of 3D Objects in Immersive Virtual Environments

Date: 24/07/2018

Time: 14:30

Location: Anfiteatro PA-3 (Piso -1, Pavilhão de Matemática) IST, Alameda

Advisors: Professor Alfredo Manuel dos Santos Ferreira Júnior / Professor Joaquim Armando Pires Jorge

Abstract: Object manipulation is a key feature in most virtual environments (VE), including immersive VE. The spatial input typically associated with these immersive VE can offer natural metaphors, allowing users to directly grab, move and rotate objects in a similar way to how it is done in the physical world, making manipulations feel more natural. However, mid-air gestures compromisse manipulation accuracy, whether due to limitations in tracking solutions or the human dexterity itself. In this research, we aimed at reducing the impact of the lack of precision when interacting with 3D objects in mid-air within immersive VE. After surveying the state-of-the art on object manipulation following several interaction paradigms, we began by assessing the performance of existing mid-air manipulation techniques in both semi and fully-immersive VE through user evaluations. Our findings suggest that, if no restrictions exist, the best approach is to use exact mappings, within a fully-immersive environment. Focusing on increasing the precision of object manipulation in mid-air, we investigated if it can benefit from separating degrees-of-freedom (DOF), which has been proved useful in other interaction paradigms. Our results showed that single DOF control can improve precision at the cost of additional time for complex tasks. To test if it can be combined with scaled translations for increased precision, and if custom transformation axes could perform faster than using axes from fixed frames, we developed two novel manipulation techniques. We found that no significant improvements came from scaling down isolated translations, and that users favored 3-DOF manipulations above all, while keeping translation and rotation independent. The accuracy of mid-air gestures also play an important role in selecting objects outside arms’ reach. We developed a new selection technique for immersive VE, which combines cone-casting with na iterative progressive refinement strategy, teleporting users closer to intersected objects. Results of a user evaluation revealed our technique as a versatile approach to out-of-reach target acquisition, combining accurate selection with consistent times across different scenarios. In conclusion, we have validated our thesis, which states that DOF separation and iterative progressive refinement strategies can be successfully used to provide more effective mid-air interactions within immersive virtual environments.