BaWeberMax

Chair for Computer Aided Medical Procedures & Augmented Reality
Lehrstuhl für Informatikanwendungen in der Medizin & Augmented Reality

# Investigating Haptic Interfaces for Viewpoint Control Metaphors in Virtual Environments

Thesis by: Maximilian Weber
Supervision by: Marcus Tönnis and Amal Benzina

We don't have force feedback light. Therefore we use haptic devices. This is part of the project VirtualArabia integrating one of the best force feedback devices available on the market.

## Introduction

Phantom 3.0 6DOF.

Coordinate System of the input device.

Haptic Feedback can play different roles in supporting the user navigating through Virtual Worlds. An appropriate device can give useful hints on how to move a spatial input device. It also can help to do experiments testing specific aspects of spatial manoeuvring. Difficulties lay in the intuitive aspects since there is no clear daily life experience that can be mapped to this experience.

This bachelor thesis continues the work of a diploma thesis by Nicolas Heuser and a bachelor thesis by Sandro Weber. Both investigate a two handed input method using a tablet computer. A result is, that some input metaphors are unambiguous in respect to the holding angle of the input device.

The initial holding angle when starting a manoeuvre is supposed to be the decisive factor. To verify that, a user study has been conducted.

## Holding Angle & Force Feedback

Upright Holding Angle.

Flat Holding Angle.

Blocking the holding angle.

The crucial part when it comes to the usage of metaphor based navigation is the holding angle of the input device. The holding angle is the rotation around the local x-axis of the input device. To do precise measurements on the one hand, the force feedback device is mounted on the tablet computer. On the other hand, this setup allows the controlling of the device's holding angle.

The physical model to simulate a blocking effect is a linear spring force using a very high spring constant. This way, the simulated stiffnes is sufficient to let the probands feel the bounds of the desired angular interval.

The holding angle is measured between the Z-axis of the local device coordinates and the Y-axis of the room coordinates. An upright holding angle means small values of α and a flat holding angles stands for high values of α.

The car driving metaphor.

The windowframe metaphor.

The airplane metaphor.

Especially the car driving metaphor, the airplane metaphor, and the windowframe metaphor are considered in this work. The idea is to do experiments on how probands perform the accomplishment of curve manoeuvres with different holding angles.

The windowframe metaphor and the airplane metaphor are exactly the same when looking at them from the perspective of the device's local coordinate system. But in the context of the room coordinates, the holding angle makes the difference for the interopretation of that rotation around the Y-axis.

## Experimantal Setup

Final Setup at the FRAVE.

First Approach using a tunnel visualization.

The user study has been conducted at the FRAVE. In a first approach, a tunnel has been used to guide the probands through the virtual world. But this concept failed because it confused the users who focused their concentration on not leaving the bounds of the path visualization. An arrow has been used to indicate a manoeuvre, instead. The Phantom Force Feedback device was put directly in front of the large monitors of the FRAVE. Every proband had to accomplish 3 manoeuvres with different initial holding angles, each.

The mobile device was attached to a marker tree. This way, position and orientation could be determined using an optical Tracking System (Infrared). This data could be used to calculate the new position of the virtual camera within the terrain for every frame.

To distribute the graphical output over multiple workstations with multiple displays, the Equalizer Framework has been used ontop of OpenGL?.

ProjectForm
Title: Investigating Haptic Interfaces for Viewpoint Control Metaphors in Virtual Environments
Abstract: A major issue in Virtual Environments is the process of navigating through a Virtual World. The underlaying base concept for the interpretation of the user’s input in such a setup is the usage of Navigation Metaphors. By way of example, holding the input device vertically like a steering wheel implies a car driving metaphor, whereas the horizontal usage like a gamepad indicates a mental model of flying an airplane. To get insight whether there is a specific holding angle that marks the usage of a certain metaphor a user study had been conducted. The starting point for this objective was the assumption that the current metaphor depends on the holding angle of the input device when the user begins a manoeuvre. The input method was the two handed, spatial moving of an optical tracked tablet computer. Before each manoeuvre, specific degrees of freedom of this device have been blocked using a haptic feedback unit installed on it.
Student: Maximilian Weber