# GazeRayHand: Combining Gaze Ray and Hand Interaction for Distant Object Manipulation
## 4 User Study
### Procedure and Evaluation Measures  
On arrival, participants were given a written explanation of the purpose and procedure of this experiment. Once they agreed to participate, they filled out a demographic questionnaire asking about gender, age, hand dominance, and VR experience. They then received verbal instruction about the equipment and interaction techniques. Participants sat on a chair in a designated area and were asked to select their preferred hand and use only that hand. They wore an HMD and calibrated the eye tracker. Once ready, they practiced each experimental condition by translating and rotating three cubes (0.5 m width), located 3.5 away and 1 m above the user. After becoming familiar with them, they performed the experimental task.  
In the experimental task, we adjusted the the object height based on the height of the HMD worn by the participant. The order of the four experimental conditions was counterbalanced using a Balanced Latin Square design. During the experiment, we measured the following objective measures for each experimental condition:  
* Total Manipulation Time: total manipulation time (in seconds) that participants spent to complete a task with a given condition.
* Coarse Manipulation Time: the time (in seconds) that participants spent for roughly matching the rabbit and target within 10\({}^{\circ}\) and 0.1 m in rotation and translation, respectively.
* Fine-grained Manipulation Time: the amount of time (in seconds) taken until completing a rabbit manipulation after the moment of roughly matching the rabbit and target (Total Manipulation Time = Coarse Manipulation Time + Fine-grained Manipulation Time).
* Total Translation Distance: accumulated distance (in meters) that the object has been translated during the manipulation.
* Total Rotation Degree: total amount of rotation (in degrees) that the object has been rotated during the manipulation.
* Total Hand Translation: total translation distance (in meters) that the participant's hand moved for the manipulation. For Gaze&Pinch, which uses both hands for object rotation, we accumulated the distances of both hands' movements.
* Total Hand Rotation: the total amount of hand rotation (in degrees) performed during manipulation. For Gaze&Pinch, we accumulated the amount of both hands' rotation.
* Total Head Translation: total translation distance (in meters) that the head moved during manipulation.
* Total Head Rotation: total amount of head rotation (in degrees) that was performed during manipulation.  
After completing the eight trials for each experimental condition, participants answered a set of questionnaires: Borg Category-Ratio 10 (Borg CR10) [29; 39], System Usability Scale (SUS) [40], NASA Task Load Index (NASA-TLX) [41], and the short version of the User Experience Questionnaire (UEQ-S, measuring pragmatic and hedonic qualities) [42]. Participants were allowed sufficient rest after completing a set of eight trials in each experimental condition. Upon completing all four experimental conditions, participants ranked their preference for the four conditions, from 1 (best) to 4 (worst), and were interviewed about the pros and cons of each condition. The entire experiment took about 70 min per participant. Participants received USD 10 as a reward and were free to withdraw at any time during the experiment.