Digital Fulldome Limit of Visual Acuity

This study on the theoretical visual acuity limit of a digital fulldome projection system is performed in support of a design science solution entitled SPHERICAL METAPHOR (SPHERIPHOR) FOR GEOSCOPE MULTI-DIMENSIONAL DATA VISUALIZATION. This fulldome immersive digital technology design science artifact is inspired by Buckminster Fuller's concept for a Geoscope. This is one of a series of studies for the creation of a visual metaphor for representing complex data clusters in spherical space.

The technology demonstration was presented at the 5^th International Symposium on Digital Earth (ISDE5) on June 7, 2007 at the University of California Berkeley.

For more information see:

Spheriphor

Main Page

Buckminster Fuller Challenge
Advanced to 2nd Stage
Q and A - Dome Projection System
Fulldome Visual Acuity
Spheriphor Study 01
Spheriphor Study 02
Spheriphor Study 03
Spheriphor Study 04
Spheriphor Study 05
Spheriphor Study 06

The term SPHERIPHOR and the special spelling SPHΘRIPHΦR using the Greek letters phi (Θ) and theta (Φ) are trademark words coined by the author/inventor Thomas J. Greenbaum as a compound of the words "SPHERIcal" and "metaPHOR." Included in the Spheriphor Studies are 3D images and animations rendered with POV-Ray. Examples of POV-Ray scene description language source code is provided "as is" for the reader to use and experiment with.

This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 License.

Objective
Background Research
Pixel Limit for a Fulldome
Conclusion

Objective

The intent of this study is to answer the question:

What is the theoretical resolution of a fulldome, fully-immersive digital experience at the limit of visual acuity?

By calculating this theoretical requirement we can then establish a technology goal. With the goal clearly established we can examine the gap between current technology and what it will take to create a fully-immersive environment at the limits of visual acuity.

A digital fulldome projected at the limits of visual acuity should be indistinguishable from reality. Add to this a surround sound audio system and a user centered within the dome would have trouble separating the virtual experience from reality. This may be compared to the concept of the Star Trek "holodeck."

Background Research

See Notes on the Resolution and Other Details of the Human Eye http://www.clarkvision.com/imagedetail/eye-resolution.html.

Summary of the Findings

Visual acuity is defined as 1/a where a is the response in x/arc-minute.
When x is defined to be a line pair, as is normally done in modern optics, the 1/a value is 1.7 under good lighting conditions.
The acuity of 1.7 corresponds to 0.59 arc minute PER LINE PAIR.
Thus, one needs two pixels per line pair, and that means pixel spacing of 0.3 arc-minute.

Print Example

Consider a 20" x 13.3" print viewed at a distance of 20".
The Print subtends an angle of 53 x 35.3 degrees, thus requiring 53*60/.3 = 10600 x 35*60/.3 = 7000 pixels, for a total of ~74 megapixels to show detail at the limits of human visual acuity.
The 10600 pixels over 20 inches corresponds to 530 pixels per inch.

Pixel Limit for a Fulldome (Fulldome Visual Acuity Limit)

In the above print example, Clark concludes that at a distance of 20 inches the visual acuity resolution corresponds to 530 pixels per inch. Therefore, we need to calculate the surface area of a hemisphere with radius equal to 20 inches.

Surface area of a sphere:

a = 4πr²

Given:

r = 20 inches
Area of sphere, a = 5027 square inches
Area of hemisphere (fulldome) = 2513 square inches

Therefore:

Total number of pixels = [(2513 square inches) x (280,900 pixels per square inch)] =
705,901,700 pixels or about 706 megapixels.

Conclusion

A digital fulldome projection system with a ~700 megapixel capability will achieve a resolution at the limit of the visual acuity of the human eye. A person standing at the center of such a dome, viewing a photo-realistic rendering should not be able to tell the difference between the simulated and real visual experience.

It is assumed that a moving image, or video on a digital fulldome would not have to be shown at the same resolution in order to simulate reality. This is due to the fact that the eye fills in the fine details when viewing movement.

A 700 megapixel fulldome projection system is a daunting technological challenge. Such a system would require innovative breakthroughs in several technology areas. For example, this could create a demand for a new multicore CPU/GPU.

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