Course Information

This project was developed as part of the master’s course “Interaction in Mixed Reality: Advanced Topics“, which builds on foundational MR interaction techniques taught in “Interaction in Mixed Reality: Basic Concepts.“ The course introduces students to advanced topics, including perceptual illusions, beyond-real interactions, augmented and diminished reality, and hybrid user interfaces.

In the second half of the semester, students apply this knowledge by creating a functional prototype using devices like the Meta Quest 3, HTC Vive, and other state-of-the-art MR hardware. Our team, consisting of Simon Schwitz and Nader Halwani, created a prototype exploring locomotion redirection techniques for VR.

Motivation

Walking is one of the most natural and immersive ways to navigate virtual environments. However, most real-world spaces available to users, such as laboratories, living rooms, or dedicated VR areas, are significantly smaller than the environments represented in VR. Redirection techniques aim to overcome this limitation by subtly manipulating how users move in the physical space, allowing them to experience virtually infinite environments without crossing physical boundaries. Even minor manipulations in the virtual scene can significantly influence how people walk in the real world, making redirection a powerful tool in MR system design.

Implemented Techniques

To explore the practical potential of redirection, we implemented three complementary techniques:

• Freeze and Turn
• Rotation/Curvature Gain
• Architecture Manipulation

Each technique approaches the problem differently, ranging from explicit interventions to subtle, almost imperceptible manipulations.

Freeze and Turn

Freeze and Turn is the most direct form of redirection. As soon as the system detects that the user is close to the edge of the play area, the virtual experience briefly pauses. The user is then instructed to turn around in the physical world, typically by about 180 degrees. Once they have turned, they may continue walking forward through the virtual environment, even though their real-world direction is now reversed.

This method is easy to understand and guarantees safety, but it can break immersion because it introduces a noticeable interruption. If the play area is small, the frequency of these pauses increases, making the experience feel less fluid.

Rotation / Curvature Gain

Rotation or curvature gain aims to be subtle rather than explicit. Instead of pausing the experience, the system slowly rotates the virtual world around the user whenever they take a step forward or backward. Users naturally correct for this slight misalignment by adjusting their walking trajectory, resulting in a curved path in the physical space while they perceive themselves as walking straight in the virtual environment.

This technique is highly immersive when tuned correctly, as many users do not consciously detect the manipulation. However, its effectiveness depends heavily on the size of the play area and the user’s sensitivity to visual motion.

Architecture Manipulation

The third approach, architecture manipulation, incorporates redirection directly into the level design. We created a virtual environment featuring multiple doors and transition points. Whenever users interacted with a door by opening it, closing it, or stepping through it, the world around them subtly rotated. Drawing the user’s attention towards the interaction, the manipulation often went unnoticed.

This method combines redirection with environmental storytelling, making it feel natural and unobtrusive. Designing such environments, however, requires careful planning to ensure that architectural elements occur at moments when users are naturally distracted.

Conclusion

Throughout development and testing, it became clear that subtle methods preserve immersion far better than explicit ones. Curvature gain and architecture manipulation enable continuous movement, rarely disrupting the experience when properly tuned. Freeze and Turn, while reliable and easy to implement, is best suited as a fallback mechanism or for applications where precision is critical.

The prototype was evaluated as part of the lecture’s exam on both the HTC Vive and Meta Quest 3 headsets. Since both platforms offer reliable positional tracking, the redirection techniques performed similarly, and no system-specific adjustments were required.