Figure 13 – uploaded by Ed Lantz

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Figure 13. Multipurpose event dome configurations (© 2019 Vortex Immersion Media, Inc. Used with permission) — Figure 13 Multipurpose event dome configurations (© 2019 Vortex Immersion Media, Inc. Used with permission)

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Figure 1. Cutaway of geodesic dome with hanging vinyl cover and internal negative-pressure screen. (©2019 Pacific Domes, Inc. Used with permission.) Building digital planetariums and giant screen theaters is an expensive affair. Less expensive prefabricated mobile dome theaters are a popular alternative and can be found at festivals, sporting events, conventions, and more. The most common mobile domes utilize a geodesic frame with vinyl cover and negative pressure internal fabric projection screen supported via a suction fan as shown in Figure 1. With a UV resistant heavy vinyl cover, HVAC and an interior deck or slab, these structures can also be used as semi-permanent theaters up to 37 meters in diameter with a lifetime of 20 years or more. Air-supported domes are also popular for larger venues of 60 meters or more. These structures require positive air pressure requiring revolving doors or airlocks to maintain interior air pressure.

Figure 3. Standard ergonomic field-of-vision for a) seated and reclined and b) standing

As shown in Figure 4 (a), the standing configuration provides the narrowest vertical FOV in natural standing head position. Viewers must look up to maximize their sense of immersion. Slightly reclining seats as shown in (b) provide viewers with an improved FOV. Note that the front seats would ideally be reclined at a greater angle to maximize immersion. Tilting the dome as shown in (c) improves immersion, especially for viewers towards the front of the theater. Increasing dome tilt and adding stadium seating as shown in (d) maximizes vertical FOV and is an optimal design for immersive theater where it is desired to deliver a collective audience experience. Optimal immersion is also attained when floating or reclining in a level dome as shown in (e), or when rows are vertically stacked in a 90-degree tilted dome as shown in (f). Figure 4. Unidirectional dome designs including a) standing, b) seated, c) seated with dome tilt, d) stadium seating with dome tilt, e) floating or reclined viewing and f) vertical seating

Figure 5. Variations in dome tilt and formation of a virtual “gravity horizon” Another variable in screen design is the vertical elevation of the dome with respect to dome center (sometimes called “sweep” or “aperture angle”). Most planetarium domes are perfect hemispheres (180-degree vertical elevation) for legacy reasons. There are, however, advantage: to constructing domes that are less than a hemisphere as shown in Figure 6. Hypohemispheric dome screens have less surface area and thus tend to cost less, are easier to project onto using multiple projectors, and result in improved contrast as we shall see. The 165-degree dome was originally chosen by IMAX Corp. since it dropped the spherical center closer to the audience’s eye plane which minimizes geometric distortion as viewers move off-axis.

Figure 6. Variations in dome vertical elevation or aperture angle Finally, we look at image field-of-view and placement of audiences within immersive spaces and placement of the springline. It is certainly possible to completely surround a viewer with complete sphere with no springline at all. Full-sphere theaters have been built for research such as the AlloSphere (Kuchera-Morin, et al., 2014), and have found applications in exhibitions and museums (Maceda, 2015; GOTO, 2016; Proctor, 2017).

Figure 7. Sightline criteria for placement of springline and stage

a) Full-frame nisneye - limited to vertical pixel resolution Over 16U degrees D) lruncated Nsheye - utilizes full horizontal resolution over |oU aegrees Dut truncates ima In general, most single-projector systems are found in smaller domes up to 10-12m in diameter and require 4k or 8k pixel resolution projectors for best results. The projector is ideally placed ir the center of the dome as shown in Figure 9 (a) but may be placed towards the front or rear of th dome with appropriate digital remapping and intensity gradient compensation. Single projector systems are simpler to setup and align and are therefore much better suited to portable dome applications. Dual fisheye configurations are also possible that use a second projector to fill in the truncated area as shown in (b). A single edge-blend between two projectors is accomplished using geometric warping and soft-edge masking. Navitar (2019) publishes an excellent tutorial on single and dual projector dome systems. Figure 8. Fisheye projection options for single projector with 1.9:1 aspect ratio

Multi-Projector Edge-Blended Systems Figure 9. Single, dual & six-projector edge-blended projector layout

Figure 10. Basic multiprojector display system for live-performance dome theater

Table 1. Projector luminous flux (in lumens) versus screen luminance (fL) for various dome diameters. Assumes screen reflectance of 0.2, dome elevation 165 degrees and projector overlap factor 0.8.

Figure 11. Eye-limited resolution as a driver for pixel resolution at various viewing locations expressed as a fraction of dome radius (scales with dome size), with resultant pixel width for various diameters Large-scale digital planetariums and giant screen domes typically employ an industry standard of 4k x 4k dome master resolution with a small number of 8k x 8k systems deployed. As shown, a resolution of 5.4k is required to match the resolution of the human eye from the rear-most seat. An 8k dome display falls below eye-limited resolution just behind dome center. And if eye- limited resolution is desired at the front row—assumed to be 0.5 radii in front of dome center—a 22k dome master is required.

Figure 12. Crossbounce of incident light ray with luminance (L) onto screen with reflectance (r) In Figure 12 we illustrate crossbounce by tracing a single ray of light with illuminance L. This ray strikes a grey Lambertian screen (which scatters equally in all directions) with reflectance r. The resulting image illuminance seen by an observer is therefore proportional to r. Crossbounce light is attenuated a second time relative to the primary reflected image. Therefore, the intensity of a crossbounce ray varies proportional to r? as r is varied. The overall crossbounce contrast ratio (r/r?) varies approximately as 1/r. So as the reflectance is lowered, crossbounce contrast, which is inversely proportional, increases.

Checkerboard contrast as a function of dome gain and vertical elevation is shown in Table 2. Many traditional planetariums utilize hemispheric screens (elevation of 180 degrees) with a gain of 0.65 which works well for star projection where the imagery is mostly black with pinpoint stars and planets. However, this results in a checkerboard contrast of less than 4:1 which is concerning for cinematic content creators as it severely limits image quality for brighter content. In comparison, digital cinema systems are generally expected to maintain checkerboard contrast of 100:1 or more. Where r is the dome screen reflectance (also called gain) and @ is the vertical dome elevation.

a) Home viewers with multicast VR headsets Figure 15 — Streaming options for live immersive media experiences Source: Vortex Immersion Media, Inc.

Figure 18. EMC World 2013 exterior and interior dome Source: Vortex Immersion Media, Inc. In 2012 VIM worked with EMC brand managers to craft a story to fly audiences through a “dataverse” showing how private and public clouds could be trusted to serve corporations. In 2013 the same team created a Tron-like world that we navigated in a “dataship” while that illustrated tools for IT security and governance. Both pieces included animation with live-action elements and visual effects produced with support from Pixomondo, an academy award-winning visual effects house that won three Emmys for their dragon animations on HBO's Game of Thrones and an Oscar for its work on Martin Scorsese's Hugo).

Figure 13 – uploaded by Ed Lantz

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