Q&A - Dome Projection System

The following Q&A discussion concerns a fully portable digital fulldome outside-in projection system presented as 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. Also discussed is the concept of a visual metaphor for representing complex data clusters in spherical space.

The technology demonstration was presented at the 5th 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.

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Dome Projection System Questions and Answers

Q: How is the dome or icosahedron being raised up off of the floor like in your digital model?
A: They are raised up using strong monofilament fishing line that is attached at several points. The line is 80-100 pound test (tensile strength). The line would almost be invisible at a distance. In fact, many magicians use this in their magic tricks.

Q: Why does the system need to be raised up on its legs and then flattened out before it can go into its projection configuration?
A: The flattened configuration is useful to project downwards onto the floor. With the Dymaxion map on the floor beneath the frame the projectors can overlay graphics and data onto the map. This allows an intimate gathering of people standing on the floor to discuss the map and the overlaid data.

Q: Where do the dome and foldable Dymaxion map come from? They seem too big to fit in the box the rig came in, unless they are collapsible.
A: I don't show this part very well in the video. These appear to come onto the floor from somewhere "off stage." They would be packaged along with the frame in the same box. The map would ship folded up and the dome would be shipped disassembled. The dome would come in several sections corresponding to the projection areas. The map and dome would be taken off to the side until the frame is expanded. It would have been too complicated to show all of this animated and the time was limited.

Q: Can the projectors project onto all sides of the icosahedron at once, or just the top half? If not, why use an icosahedron at all and not just the dome? Would you be able to see the top sides of the projection on this scale? I guess bleachers would help.
A: The icosahedron map is folded in order to demonstrate to the audience the principle behind the map. Buckminster Fuller describes this sequence in his original concept for a Geoscope. The map is most useful in its flat configuration. I didn't intend initially to project onto the folded icosahedron. However, this could be another useful feature that could be developed.

Q: Do you stand inside the dome to look at the projections? If not, why did you raise it off the floor?
A: Yes, for some types of displays it would be very cool to stand inside the dome. This would be similar to a planetarium dome like Lodestar. UNM ARTS Lab has a mini-dome (15 foot diameter) that you sit under. In this way a fully immersive experience can be created.

Q: If only six projectors are needed to cover a full dome, why are there eight of them? Hmm, maybe that's for projecting on the floor or something.
A: Yes, all eight are used to project onto the floor.

Q: I get the outside-in name for the projection system. Usually projecting onto a dome you are sitting inside of it and there is a rig in the middle that projects onto the opaque inside surface right?
A: Yes, you are definitely right about this. This is what makes this invention unique. It frees up the inside of the dome by putting the projectors on the outside.

Q: I'm just not sure if this projects from the outside to the outside of an opaque dome or from the outside to the inside of a transparent or translucent dome.
A: This is a translucent dome. It is made of material similar to rear-projection screen material.

Q: I guess if you're on the inside being projected on from the outside you can't cast shadows on the screen.
A: That is definitely one of the benefits. It is also potentially brighter.

Q: But if you could make some kind of transparent material that would still hold the image of the projection (I don't know how that would work exactly...) you could just hide an inside-out version like at the planetarium inside the dome and look at the outside as well.
A: Not sure if that can be done with a transparent material. The idea is that by freeing up the inside of the dome you can make a very lightweight dome and have the option of viewing from the outside or the inside depending on what you are presenting. Also, the social interactions and perceptual viewpoints are different.

Q: I think there's just some problem inherent to projection I don't know about that this must solve. How did you get the little projectors to make the exact shape you needed to tessellate onto the dome? Is it a frame around them or something with the lens itself?
A: Very good question. Most existing projection systems use masks in front of the lens. Alternatively, one could also digitally mask the image.

Q: What kind of projection for the computer screen does or would the program that makes the images to put onto the dome use? I saw your three-dimensional version of a polar coordinate system (way cool) and I get how it is used on the globe or dome itself I'm just not sure how that would work on a flat computer screen to make the maps and charts.
A: This is where the concept of a UV mapping system comes in. You are right that the flat image must be distorted to correctly display on a spherical surface. An algorithm must be developed to do this. This image processing occurs in a software application which renders a corrected image.

A: Does the user make them by sections for each of the projectors or as one big, connected image and the program or the projectors sort it out for themselves?
Q: Excellent deduction. It could be done either way actually. I saw a 35 megapixel projection wall at the Sandia National Laboratory that used a 4x6 array of high-resolution projectors. A total of 24 projectors were aligned on a specially engineered rack behind a ground plate glass wall in a rear projection configuration. The images from each projector were lined up with such precision that the pixels from one projector butt right up to the pixels from the adjacent projector to form a seamless image. You could not tell where one image stopped and the other started. Each of these projectors was controlled by a single computer. So there were 24 computers that were working together to create this display. As you can imagine this was a very expensive system. Probably cost millions of dollars.

However, my idea would be to use a single multi-processor computer with powerful video cards that have multiple video outputs. The separate images would be controlled by software on this single powerful computer.

Q: I really like how you used the gym floor as an example for the kind of surface to set this up in. It's familiar and gives a good scale and points of reference. A great choice. I guess in real life you might run into some problems with small gym doors and the kind of basketball hoops that fold up onto the ceiling when they're not being used but the only gym with a painted floor I've been in for a long time was my middle school one and that was pretty small. I suspect college gyms are more than big enough for your example, since they can hold an audience.
A: Thanks, but it was not entirely original. The Buckminster Fuller Institute has educational programs and a Design Science Laboratory course that uses a huge Dymaxion map which is typically laid out on a gym floor. You are right that in some spaces there may be obstacles to using this system. Yes, a college gym would be much easier to deal with, and that is what I used for the scale.

Q: It must be really complicated having the projected image animated, but it probably has to be so that people can see all the sides of it without having to walk all the way around the gym.
A: Yes, it would be necessary to have the image animated so that people could see all sides of it. The software application will take care of this rotation. Rotating the image is really not that difficult once the 3D virtual model is created in the computer. That is the hard part.

Q: This is not really a question, but it seems to me that this kind of setup would be perfect for museums to show demonstrations for things like meteorology and plate tectonics and what the surface of various stars and planets look like. It would be so much easier to understand than a flat map or painted globe or even a 3D model on a flat screen. I bet for a permanent exhibit like a museum you could sink it under a glass floor and view it by walking over the top of it.
A: Awesome idea of having people being able to walk above it. Thanks for that idea!

Q: Someday there may be a system with a little dome the in the middle of a really big dome with projectors putting images on the outside of the little one and the inside of the big one. This way you can model the earth and the solar system at the same time.
A: Another great idea! Nested domes with people walking around in the space between and images projected on both. That is a very exciting idea. The projectors could be hidden inside the big dome.

Q: It is hard to think of uses for it outside of a world map. Globes are really seldom used for anything else. But that's what makes it so special isn't it? Anything cyclical like yearly or monthly timelines would work well and you could show hierarchy scales easily.
A: Wow, that is very observant. You have hit on a very significant point. Cyclical data displays very well in a circular arrangement. There is actually quite a bit written about this. For example, there are special charts called radar graphs that use polar coordinates. The debate is that these graphs are mostly difficult to read except for when they depict cyclical data. You are a genius; I have no doubts.

Q: It seems to me that right now these are mostly just simple uses for this very complex and ingenious invention. That's probably because its new and I'm just not used to having to think about it.
A: Yes, it is new and maybe if it gets built then people will discover all sorts of uses for it. I would love to have you on my team to discover these new uses.

Q: What other configurations have you thought of for your invention? Like, what else can it project onto? Although the curves are much, much more complex than just a sphere if it could be made to project onto an oversized mannequin of some sort. Medical schools could use it as kind of an ultimate non-organic teaching tool. But man oh man I wouldn't want to be the one to have to come up with a mapping system for that program!
A: Okay, this is another big WOW! What an idea! Projecting onto a mannequin would be very, very cool. Of course, you hit the problem right on the head; the mapping system would be a big challenge. However, all you need is the math...

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Copyright 2012 by Tom Greenbaum. Creative Commons License Some Rights Reserved
email: tom@karmatetra.com

Albuquerque, New Mexico