## 6 Results and Discussion
### Discussion  
The experiments aim to understand the influence of an immersive visualization interface in relation to spatial and movement perception. To study these factors, we designed several tasks where users had to indicate a 3D position in space based on visual feedback mediated by technological means: a single monitor with a wide single view of the remote scene (traditional interface) versus multiple partial views of the scene naturally acquired while moving their head. The experiment described in Task 1 demonstrates that, if the workspace of interest is all within the field of view of the HMD, there is no benefit using an immersive interface. The participants did not feel the need to move their head to accomplish the task of pressing key blocks, not gaining depth perception. The time performance was similar for both visualization interfaces. Task 2 experiments show that an immersive interface outperforms the traditional interface when the workspace of interest is larger than the HMD field of view. Comparing a fixed wide view of the scene with a set of partial views of the scene provided by the head user movement, the last approach improves depth perception due to motion parallax. There is an enhancement of spatial and movement perception demonstrated by the accuracy and speed to accomplish the pick-and-place task. A consequence of the limited FOV of the remote camera (immersive interface condition) was that users moved their head more frequently. Nevertheless, this active spatial perception allowed users to focus their attention on one region of interest, minimizing the workload. All participants took advantage of the touch sense to localize objects and to perceive the height of the gripper tip. Users' common procedures consisted of moving the gripper in contact with the table until reaching the object. This way, the user compensates the lack of height perception through vision while moving the gripper or the tip of the stick. In Task 3, we tried to evaluate the accuracy of the movement without the help of haptic feedback. Here, the time performances to follow a 3D path did not present a significant difference while comparing both interfaces; however, there was a significant improvement concerning the accuracy of the 3D movement. This is shown by the lower number of hits occurring while using an immersive interface. Concerning the latency, there was no communication delay due to the proximity of the devices. However, special care was dedicated to tuning the two-step motor lag responsible for the pan and tilt movements of the camera, because faster movements of the head were tracked by the HMD, but were not properly executed by the motors (faster DC motors are advisable). The cameras of the system enabled the video frame rate (\(>=\)30 fps), thus fulfilling the requirements for handling the tasks. The experiment referred to as the \"control task\" was initially executed to evaluate the weight of each mediation component in the immersive system. The no mediation task \"direct vision (binocular stereo) + hand\" became our ground truth. Users handled the block with their hands, looking directly with their eyes, and took \(\mu_{t}=8.75\) s (\(\sigma_{t}=1.39\)) to accomplish the task. With the introduction of a tool (\"direct vision (binocular stereo) + gripper\"), users took \(\mu_{t}=30.87\) s (\(\sigma_{t}=14.9\)). The gripper disturbance caused an increase of 252% in time performance. Movement perception of the gripper in relation to the objects became an issue. Using see-through HMD only (\"HMD indirect vision (mono biocular) + hand\"), users took \(\mu_{i}=15.62\) s (\(\sigma_{i}=2.92\)). The see-through HMD disturbance increased 78% in time performance. The limited FoV contributed to such disturbance, and participants quite frequently used their other hand to self-position their body in relation to the workspace. With the introduction of the gripper and see-through HMD (\"HMD indirect vision (mono biocular) + gripper\"), users took \(\mu_{i}=41.3\) s (\(\sigma_{i}=8.5\)).