## 7 Validation with Users
### Procedure, Tasks and Experimental Design  
Each user has been asked to fill in an informed consent as well as a small survey regarding their previous experience with AR. During the test, the facilitator used a written script, so all participants received the same information. The study has been divided into 5 tasks, labelled from T1 to T5. Tasks 1 to 3 make use of the Haptic Inspector prototype of Section 6.1. Tasks 4 and 5 are based on the Simon prototype of Section 6.2. In order to avoid the learning effect due to specific use of Ultrahaptics, before starting the test, each user experienced a short application example (moving bubbles, extracted from the Ultrahaptics Demo Suite). In this short demo, participants position their hand on the Ultrahaptics,  
Figure 10: Second proof of concept: Simon game based on the combination of Augmented Reality (AR) and haptic feedback. so they can perceive the feedback and the interaction range. The facilitator has also been in charge of aligning the systems through the automatic mode described in Section 5.1. Next, we detail the purpose of each task together with its workflow:  
* **Task 1, perception of the contribution of haptic feedback over AR visualization for inspection tasks**: This task has been designed to offer the user a first contact with the combination of haptic feedback and AR or with HARptic. The basics of the system are introduced to the participants: they will be able to haptically inspect different geometrical figures that will be visible through HoloLens, and they can _inspect_ with their hand. Participants are not told how to actually inspect the figures; their own interpretation of the action will condition the way they interact with the views. This process is repeated for the 10 images in Figure 11. For each figure, the exploration time is saved. Additionally, the user is asked to rate from 1 (very difficult) to 5 (very easy) to which extent the figure would be guessable only through the delivered haptics (no visualization available). The images chosen to be included in the test (for Tasks 1-3), are divided into the following groups: A first group of basic geometries (_pyramid, cone, sphere, hemisphere, cube, and cylinder_), a second one of more complex geometries (_octahedron and torus_), and one last group of compound figures (_house and arrow_) thought to simulate objects. Figure 11 shows how figures are presented to the users. * **Task 2, Ultrahaptics-based haptics expressiveness for shape identification**: In this task, the user has to guess the shape of the object under exploration only relying on haptic feedback. The system provides the haptic representation of different 3D figures, and the user has to guess the object identity from the ones available in a list. The participant's guesses are stored as well as the time required to give an answer. The number of hits is not revealed to the user until the entire task has been completed, since after the task, a questionnaire on their perception of the task difficulty is administered. The figures are the same as that in Task 1 without repetitions. Figure 12 shows three participants while they are exploring the harptic figures. The captures have been taken using the HoloLens client. Figure 11: Set of figures used for the development of Tasks 1–3. * **Task 3, usefulness of haptic aids for AR resizing tasks**: For this task, visual and haptic representations are again merged and delivered. In this task, the system presents the participant a certain figure with preset dimensions. We have preset a virtual ground at 17 cm from the surface of the Ultrahaptics; thus, every figure stands over this ground. With this information in mind, participants are asked to resize the figure to reach a given dimension (height). A haptic anchor on the target height is deliver through the haptic device. To perform the task, the participant must put their hand over the Ultrahaptics and move it up and down as required. The process should be supported by estimations using the augmented reality.