Objective and Subjective Reality

Week 6

Chapter 6.1 Reality Is Subjective

Objective reality exists independently of observers, while subjective reality is shaped by individual perceptions, often interpreted through personal narratives and beliefs. Visionaries like Einstein and Freud recognized the malleability of reality, emphasizing that perception is central to its essence. In VR, creators craft artificial content (objective reality) and present it to users, who then perceive it as real (subjective reality). VR allows us to aesthetically control conditions, much like a lab, enabling direct communication of these experiences to others within their own subjective frameworks. Notably, VR doesn’t need to replicate the real world entirely; it leverages the brain’s ability to fill in gaps, effectively transforming mental models and broadening understanding by focusing on presenting key stimuli.

6.2 Perceptual Illusions

Our brain requires multiple sensory inputs to process information and create a sense of direct access to the world. Because the brain is hardwired to adapt to familiar stimuli, this subconscious knowledge enables us to process sensory inputs efficiently. However, this same mechanism can lead to perceptual illusions when we encounter atypical or unexpected stimuli.

“Our brains are constantly and subconsciously looking for patterns in order to make sense of the stream of information coming in from the senses. In fact, the subconscious can be thought of as a filter that only allows things out of the ordinary that are not predictable to pass into consciousness. In many cases, these predictable patterns are so hardwired into the brain that we perceive these patterns even when they do not exist in reality.”

Below is a list of perceptual illusions covered in this book. Rather than repeating their definitions, I will briefly explain why and where each illusion should be considered/used in VR design, drawing on both the book’s insights and my own perspective.

6.2.1 2D Illusions

Simple 2D shapes can appear differently depending on their surrounding context. Perceptual illusions may occur in scale, shape, position, and other visual properties. I think this phenomenon is especially relevant in UI design within the VR world. For instance, some buttons might appear larger than others due to contextual visual effects, unintentionally leading users to select the more prominent-looking buttons. Additionally, if the surrounding walls of a room or space in a VR environment consist of parallel lines or grids, a disoriented grid may appear bent, potentially affecting the user’s sense of stability while standing in the space. Thus, VR designers should carefully account for these visual effects when calibrating VR systems to ensure a seamless and comfortable user experience.

6.2.2 Illusory Boundary Completion

The book shows that illusory contours can occur in various visual contexts, from traditional forms on a flat background to 3D virtual spaces, where they can make nonexistent 3D forms appear, and even in the real world. “Illusory contours demonstrate that we do not need to perfectly replicate reality, but we do need to present the most essential stimuli to induce objects in the user’s mind.”

I believe that using illusory contours can not only reduce rendering times but also minimize the data required to create a VR world, which is always beneficial during development. Additionally, designers can use this phenomenon to guide user attention. Leveraging the brain’s natural tendency to recognize patterns or shapes can help direct users along paths without overwhelming them or relying on overt visual cues.

6.2.3 Blind Spot

When designing VR worlds and addressing accessibility, designers should take the blind spot into account. While it is a natural limitation of human vision, it becomes more pronounced for users with vision loss in one eye or unbalanced vision. If critical user interface (UI) elements or interactive objects are placed in areas that align with the impaired side of a user’s vision, they may go entirely unnoticed.

To address this, designers should avoid placing essential elements exclusively on one side. Instead, key UI components should be distributed strategically or designed to allow dynamic reorientation to align with the user’s line of sight. Additionally, offering users adjustable settings to customize layout and object positioning can further enhance accessibility. Incorporating multimodal feedback, such as audio or haptics, to alert users to overlooked visual components can also help mitigate the impact of blind spots, ensuring a more immersive and inclusive experience.

6.2.4 Depth Illusions — The Ponzo Railroad Illusion

The Ponzo Railroad Illusion can become more prominent in VR spaces created using captured 360-degree videos or images, particularly when UI elements are placed over the scene. These environments often feature strong perspective cues, as they are pre-rendered to mimic real-world depth. Placing flat or incorrectly scaled UI elements in such scenes can inadvertently trigger the illusion, disrupting the user’s sense of realism. To avoid this, VR designers must carefully measure and adjust the sizes of overlapping elements to align with the perspective of the surrounding objects in the image.

6.2.4 Depth Illusions — The Ames Room

The Ames Room is one of the examples of depth illusion that can happen when VR designers make mistakes on building space with inconsistent perceptions, slanted walls and uneven floors. Also the illusion occurs because the room is viewed with one eye through a pinhole and I think that can link to the accessibility aspect with people with monocular vision. Since such users rely more on monocular depth cues and motion parallax, VR environments need to ensure these cues are accurate and consistent.

6.2.5 The Moon Illusion

In VR, The Moon Illusion can be applied to designing large-scale towns or cities to evoke a sense of vastness and depth. By incorporating a large moon or similar celestial elements into the horizon, designers can provide users with a strong spatial reference point. This not only helps users feel grounded within the environment but also enhances their sense of immersion by reinforcing scale and physical presence in the virtual space.

This technique is already widely used in animations and manga during zoomed-out scenes, such as in opening sequences or ending credits, to set an emotional tone or establish a grand setting. In VR, this approach can be similarly impactful, making environments feel expansive and cinematic.

6.2.6 Afterimages

Afterimages come in two types — negative and positive. Both involve the persistence of an original image even after it is no longer visible. If this illusion is unintended, it could cause nausea or motion sickness in users.

To avoid unintended afterimages in VR, balancing contrast levels is essential, as high-contrast images with stark transitions between light and dark can intensify the effect. Managing color intensity is equally important; prolonged exposure to bright, saturated colors can trigger afterimages, so using softer or more natural tones can help mitigate this issue. Designers should also limit fixation time by incorporating interactive or dynamic environments to prevent users from focusing on static elements for extended periods.

Finally, proper lighting adjustments, such as smooth gradients and reduced glare, can further minimize afterimage effects, ensuring a more comfortable and immersive experience for users.

6.2.7 Motion Illusions — Motion Aftereffects

Motion aftereffects are one of the most important considerations for preventing motion sickness in VR experiences. When creating VR environments, adding moving surrounding elements such as cars, trains, moving water, and animating billboards or other patterns of moving objects can make the virtual space more engaging, dynamic, and interactive. However, staring at the moving stimuli in the same direction for 30 seconds or more can cause the motion illusion. Therefore, VR designers should be careful not only to measure perceptible motion but also to ensure users are not unintentionally fixated on the moving stimuli for a long period of time. Additionally, designers should avoid placing these stimuli in the most easily exposed spots within the user’s view.

6.2.7 Motion Illusions — The Moon-Cloud Illusion

The Moon-Cloud Illusion is a great example of induced motion. In VR design, I think this illusion can be used to create dynamic spaces while reducing memory usage. By having smaller objects move while keeping larger objects fixed, designers can achieve a similar visual effect as if the larger objects were moving, but with a lower data memory requirement. This technique allows for a more efficient use of system resources, providing an immersive experience without the need for complex animations of larger objects.

6.2.7 Motion Illusions — The Autokinetic Effect

The key aspect of the autokinetic effect is that it decreases as the size of the target increases, due to the brain’s tendency to perceive larger objects occupying a significant field of view as stable. This suggests that to create the illusion of stable worlds in VR, incorporating a large surrounding context is crucial.

When designing spaces with minimal surrounding objects — such as environments that primarily feature UI popups or buttons for extended periods — designers should carefully consider the scale of these graphic elements. Proper scaling can help mitigate the autokinetic effect and ensure a more stable and immersive user experience.

Why Understanding Visual Perception in VR Is Important

As mentioned earlier, VR designers are tasked with “creating artificial content and presenting it to users so that they perceive it as real.” Understanding common visual perceptions is the foundation for designing virtual worlds that successfully engage and immerse users since vision is the primary sensory modality in the VR experience.

Moreover, designers should keep in mind that the brain is highly adaptable and capable of modifying its “mental model of the world to match future expectations.” This understanding is critical for creating virtual environments (objective worlds) that are perceived as intended. It also reinforces the idea that VR doesn’t need to replicate the real world entirely. By presenting only the essential stimuli, designers can allow users to fill in gaps, enhancing both immersion and engagement.

Question From the Chapter

Certain visual illusions in VR, if not managed carefully, can induce motion sickness. One example is The Ouchi Illusion. In the book, an example of this illusion (Fig. 1) features a 3” x 3” pattern that made me feel dizzy after staring at it for a short time; it even appeared to move. The author explains that the illusion arises from two differently oriented black-and-white planes (the highest color contrast), which are perceived as being on separate depth planes and can create a sense of motion.

Figure. 1 Example of The Ouchi Illusion

This reminds me of a project I worked on in 2023, designing a VR space for a baseball locker room. I selected a wooden panel wall as part of the interior design (Fig. 2) to give the space a warm ambiance and elevate its aesthetic appeal, especially since the room was intended for socializing while watching a baseball game.

Figure. 2 VR Space Design from My Past Project

In real life, wooden walls (Fig. 3) are common and do not typically cause visual discomfort or distracting illusions. However, when I applied the texture to the virtual environment and tested it with a VR headset, I experienced a mild Ouchi Illusion effect and felt dizzy. I had to adjust the texture’s contrast to reduce the effect. Despite the adjustment, I believe such patterns still have the potential to cause distracting illusions for some users.

Figure. 3 Example of Interior Design with Wooden Panel Wall

Given this understanding of visual perception, I wonder if using similar patterns on walls and floors in VR environments should generally be avoided, even though they offer many design options for creating immersive spaces. Is there a set of rules or guidelines for color contrast in patterns that could minimize the likelihood of unintended illusions like The Ouchi Illusion?