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
The technology demonstration was presented at the
Symposium on Digital Earth (ISDE5) on June 7, 2007 at the University of
- Background Research
- Pixel Limit for a Fulldome
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."
See Notes on the Resolution and Other Details of the Human Eye
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
- The acuity of 1.7 corresponds to 0.59 arc minute PER LINE
- Thus, one needs two pixels per line pair, and that means pixel
spacing of 0.3 arc-minute.
- 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
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
r = 20 inches
Area of sphere, a = 5027 square inches
Area of hemisphere (fulldome) = 2513 square inches
Total number of pixels = [(2513 square inches) x (280,900 pixels per square
705,901,700 pixels or about 706 megapixels.
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
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