Optimizing the sphere

Originally submitted to a client in response to a request to review the designs for what would become one of the world's largest spherical theaters. Specific names and media have been removed.

Spherical was newly formed and this was our first formal engagement.

Introduction

The project is the most ambitious spherical theater project in history. After developing and reviewing numerous designs, the design team has settled on a few final options. However, a few critical questions have emerged in the final design phase of the theater: What is the optimal shape and orientation for the spherical display? Should the screen be elevated or modified to provide a “proscenium” viewing area to accommodate imagery below the horizon? If so, how large should it be?

The theater design must address a number of parameters and constraints, including:

• Enable artists to deliver the highest quality immersive experiences
• Ensure the safety, comfort, and well-being of audience members
• Accommodate multiple experience modalities (traditional, immersive, tech-enhanced, and future initiatives)
• On time delivery by summer 2020
• A maximum ceiling height of 250’

The client has commissioned this report as an external expert review of their theater analysis and to suggest the appropriate selection of the current design options. The report provides a brief theoretical and historical background to some of the key issues, followed by recommendations based on the review of current proposals.

Summary Findings

• Spherical theaters must optimize screen shape, audience positioning, and the horizon line.
• If done correctly, this increases a sense of presence by helping viewers to feel “grounded” within the immersive experience. If done incorrectly, it can result in motion sickness and disorientation.
• To accomplish this, sufficient screen space must be made available below the visible horizon to provide a sufficient ground plane.
• Projecting the visible horizon below the eye level plane provides a critical sense of stability, orientation, and presence.
• Without this, viewers can feel off-balance and experience motion sickness.
• Additionally, if the visible horizon tilts too far upward, it can result in an artificially high view, appear distorted, and give the viewers neck aches.
• This understanding has emerged from decades of experiments with spherical theater design that provide historic precedents.
• Final recommendation: Having reviewed the white paper and analysis, I agree with their approach and recommendations. The optimal proposed theater configuration provides maximum space for the media plane and the proscenium. This will enable filmmakers to create content that will optimize the immersive experience by providing the audience with a sense of stability, orientation, and presence.

Getting Grounded in Spherical Perspective

The sense of immersion within dome theaters primarily derives from their use of spherical perspective. Unlike the linear perspective of traditional painting and cinema, spherical perspective replicates the full field of view of human vision. This provides a natural and intuitive immersive experience – but only when designed correctly. This requires taking into account three primary variables in the design of spherical theaters and their content: screen shape, audience positioning, and horizon line.

One of the most important consideration of the interactions between these variables is in how they enable the audience to feel “grounded.” This sense arises when viewers perceive their position in relation to solid ground, or the “gravity level horizon.” When they look from side to side, this horizon should follow in an undistorted arc parallel to the ground. This is also a function to ensure that viewers are generally located within the correct anamorphic vantage point – otherwise known as the “sweet spot” of the theater.

The sense of this gravity level horizon is a function of how the eye level plane interacts with the ground plane (Figure 1). Because the viewers are constantly immersed within the spherical scene, it is critical that the ground plane be made visible, at least occasionally. This provides an overall physical point of reference within the immersive world, enabling the viewers to perceptually orient themselves.

There are three types of possible gravity level horizons. The visible horizon is one that is clearly visible at all times, such as a landscape. A non-visible horizon is the absence of a horizon, such as a scene in which the audience is free-floating in space with no points of reference for any kind of ground. An implied horizon is present when the horizon is not clearly visible but perceptually detectable through camera motion or vanishing points, often indicated by the presence of other objects in the scene.

Part of the thrill of immersive experiences arises from the illusion of movement, namely when there are contradictions between the inner ear (the sense of balance) and ocular system (the sense of sight). During the illusion, viewers minds’ attempt to accommodate for these disparities – but there is a limit. Surpassing this limit can cause a sense of motion sickness, much like being on a never-ending roller coaster. It is critical that theaters and productions be designed to enable viewers to feel grounded by gaining a sense of orientation and balance.

The importance of this cannot be overstated, and it has long been understood as a primary design consideration within spherical theaters. Since the ground plane is below the eye level plane, it is important to extend the spherical surface below the eye level plane. Projecting the visible horizon onto a screen surface below the eye level plane provides a critical sense of stability, orientation, and presence. Without this, viewers can feel off-balance and more easily experience motion sickness. Additionally, if the visible horizon tilts too far upward, it can result in an artificially high view, appear distorted, and give the viewers neck aches.

To make an appropriate design for the theater, it is particularly important to understand how the proscenium and media plane (below the eye level plane) could provide this gravity level horizon. Fortunately, this is not the first time theater designers have faced this type of decision. Decades of real-world experience have resulted in numerous best practices within spherical theater design. It is useful to understand these and how they came about through empirical experimentation and trial and error.

Lessons from Historical Precedents

To The first spherical projection environment was the Zeiss planetarium, developed by Zeiss in the early 20th century (Figure 2). The spherical shape was chosen to replicate the visual illusion of the curvature of the sky. It was designed to mimic this perceived celestial sphere by projecting points of light onto the curved screen within the darkened theater. Every seat in the Zeiss planetarium was oriented towards the center of the dome. This omnidirectional seating configuration gathered the audience around the central projector, ensuring that the only common viewing location was around the zenith (top) of the sphere.

However, the designers also took into account the need for the audience to feel “grounded” while looking to the sky. To optimize this illusion of infinite depth, the theater extended beyond the hemisphere to enable the projection of a visible horizon line (represented in Figure 1 as a mountain range). This served as a shared ground plane against which the stars would be viewed by the entire audience. This provided a common visual reference for the audience to feel stable in order to enhance the immersive effect of the rotating sky.

This design was modified when film projection was introduced into spherical theaters. The 1939 Theater of Time and Space was designed with a unidirectional seating environment, much like a traditional cinema. Spherical imagery was projected onto a truncated hemisphere in front of the audience, combining the benefits wide field-of-view spherical imagery with the shared focus and attention of traditional cinema (Figure 3). While this forward-facing theater wrapped around the audience horizontally and overhead, it did not curve below their eye level plan. This limited the options for establishing the ground plane and gravity level horizon, so the production focused on astronomical content.

In the late 1960s, IMAX introduced a hybrid of these approaches with the Omnimax Theater (Figure 4). This design employed a unidirectional seating environment, integrating the approaches of both planetariums and spherical cinema. The Omnimax theater was tilted at 35°, enabling substantial screen space for a visible horizon line to be seen by the entire audience. This increased creative opportunities for filmmakers to explore aerial and terrestrial shots in way that the audience could experience perceptual grounding through a gravity level horizon.

Today, modified versions of the Omnimax theater design (tilted screen with unidirectional seating) have been adopted by hybrid digital planetariums and dome theaters around the world (Figure 5). While many older planetariums are limited to astronomical content by hemispherical screens with no visible horizon, these newer digital dome theaters are designed to accommodate a wide variety of production types. They extend the screen below the eye level plan to accommodate the display of a considerable visible horizon when necessary. This is widely accepted as a best practice for theaters seeking to display a wide variety of content.

Conclusions & Recommendations

This brief history of spherical theater design can hopefully inform urgent decisions regarding the theater. These previous efforts yielded invaluable insights into the nature of perception, the importance of orientation and balance, and techniques for achieving sense of grounding within immersive spherical environments. Key principles and best practices were gradually discovered by working to optimize first-person immersive experiences for large groups.

In the case of this theater, I have reviewed the client's analysis and agree with their conclusions. It provides maximum space for the media plane and the proscenium. This will be essential to provide screen surface below the eye level plane enable the content to establish a ground plane and visible horizon.

Given the ambitious scale of this project, it is all the more critical that filmmakers provide the audience with a sense of stability, orientation, and presence. This option will optimize the theater’s flexibility and creative opportunities for different experience modalities. But more importantly, it will help to ensure that visitors have immersive experiences that are both mind-blowing and comfortable – and that they will return again and again.

References

Buczek, I. (2012). The immersive dome environment (IDE): Old concept in a new light or a new hybrid medium to enhance human cognitive faculty? Technoetic Arts: A Journal of Speculative Research, 10(2/3), 247–254.

Flocon, A., & Barre, A. (1988). Curvilinear Perspective from Visual Space to the Constructed Image. Berkeley: Univ of California Press.

Grau, O. (2004). Virtual art: from illusion to immersion. MIT Press.

Griffiths, A. (2008). Shivers Down Your Spine: Cinema, Museums, and the Immersive View (1st ed.). Columbia University Press.

Lantz, E. (2007). A survey of large-scale immersive displays. In Proceedings of the 2007 workshop on Emerging displays technologies: images and beyond: the future of displays and interaction. San Diego, CA: ACM.

Lantz, E. (1995). Spherical image representations and display: A new paradigm for computer graphics. Presented at the SIGGRAPH, Los Angeles, CA: ACM.

Lantz, E., & Thompson, B. (2003). Large-scale immersive theaters. In Computer Graphics for Large-Scale Immersive Theaters. San Diego, CA: ACM.

McConville, D. (2007). Cosmological Cinema: Pedagogy, Propaganda, and Perturbation in Early Dome Theaters. Technoetic Arts: A Journal of Speculative Research, 5(2), 69–85.

McConville, D. (2014, July 7). On the evolution of the heavenly spheres: An enactive approach to cosmography (Doctor of Philosophy). University of Plymouth, Plymouth, England.

Naimark, M. (1992). Expo ’92 Seville. Presence, 1(3).

Rogers, B., & Rogers, C. (2009). Visual globes, celestial spheres, and the perception of straight and parallel lines. Perception, 38(9), 1295 – 1312.

Shaw, J., & Lantz, E. (1998). Dome Theaters: Spheres of Influence (pp. 59–65). Presented at the SIGGRAPH, Orlando, FL: ACM.

Shedd, B. (1989). Exploding the frame: Seeking a new cinematic language. Retrieved from tinyurl.com/explodingtheframe.

Schnall, S., Hedge, C., & Weaver, R. (2012). The immersive virtual environment of the digital fulldome: Considerations of relevant psychological processes. International Journal of Human-Computer Studies, 70(8), 561–575.

Thompson, B. (2004). Four Issues to Consider When Producing Fulldome Content for Wide Distribution. Valencia, Spain: IPS 2004 Fulldome Standard Summit.

Wonders, K. (1993). Habitat dioramas: illusions of wilderness in museums of natural history. Stockholm, SE: Academiae Ubsaliensis ; Almqvist & Wiksell International.

Yu, K. C. (2009). Digital Planetariums for geology and geography education: Earth visualizations at the Gates Planetarium. The Planetarian, 36(3), 6–12.

About the Author

David McConville is a designer, producer, and historian of immersive spherical media and environments. He co-founded The Elumenati, an immersive projection company that pioneered the design and use of portable digital dome theaters. His doctoral dissertation, On the Evolution of the Heavenly Spheres, examined how domed visualization environments have shaped perceptions of the world.