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Screen With 180 Degree Field of View
emj writes to tell us project jDome has started actively soliciting consumer feedback and, of course, donations. They are currently promising to deliver their "180 degree FOV monitor" this year for a pricepoint of around $200. The videos and talk have been circulating for the last couple of weeks or so, but they have added a video of the supposed tech in action. Buyer beware, but I would love to see a couple of reviewers get ahold of this and let us know what the story is.
How much more for the projector? won't come cheap no matter how you look at it.
You're not going to be able to see the whole screen without turning your head. Isn't the average human's field of view between 120-140 degrees?
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I just watched the video and it looks to me like all the have done is stretched the standard view to fill the 'dome'. This results in all objects that are at the edges of the dome to be stretched and way out of proportion. The "man at the right" is a prime example of this.
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It's a $200 white, round umbrella. Then you still have to buy your own projector? I don't see anything new, apart from a new use for an umbrella.
That looks like it would give me motion sickness for some reason. Maybe it's due to everything being stretched out of proportion and whenever you turn it's constantly shrinking and expanding. I don't know but that looked like a piece of crap to me.
You're nothing; like me.
...although it might be possible with a pixel shader, the hardware would really need to support other projection types than just standard 3-point (and with some hacking the transformation matrix, 2-point) perspective.
For a dome projection, you essentially need a linear fisheye projection out of the card, and the cards just don't do that.
You could do it in software, render a hemicube in the buffer, use a pixel shader to map the appropriate pixels onto the circle, done. Except that to get to 'done', you have to go through some very expensive (in terms of performance drop) steps.
1) rear projection onto a deeply curved screen? Getting even illumination at the edges, where the light is striking at an angle, is going to be quite a trick, due to Lambert's law.
2) How are they going to avoid the problem of washout and reduced contrast due to light from one side of the screen reaching the other side? This is always a problem with deeply curved screens. It's very noticeable in IMAX Dome (Omnimax) screens. The only system I've personally seen that avoided it was the original Cinerama screen, which was a very specially built screen made of hundreds of individual strips. And that only worked because the screen was huge and you were sitting very far from it.
Cinerama and IMAX screens are huge and far away. They're almost at optical infinity. The texture of the screen is invisible. There's very little binocular depth cues to tell you that you're looking at a flat screen, and if you move your head (as you always do unless it's in a clamp), that doesn't give you any parallax cues to speak of. This means that the screen itself is hard to see, and there are practically no binocular depth cues. That in turn means that there's nothing to contradict the numerous depth cues you get from any flat picture (light, shade, interposition, etc.--see any perceptual psychology text). The screen itself falls away, the non-binocular depth cues dominate, and you have a distinct feeling of being in 3D space.
But this is a small screen a short distance away from you. That means:
a) The texture of the screen may be visible unless they're using some rather special screen material.
b) Again, because it's a small screen a short distance away from you, there will be enough binocular disparity between your two eyes for you to form a stereo image: that will tell you that you're looking at flat image in a bowl, and in the battle between those cues and other cues, it's not clear which will win. The same thing will happen when you move your head. In fact, if you move your head a few inches, you will probably be far enough from the center, as a percentage of the radius, that the image will show geometrical distortions.
I am very, very, very skeptical that this system will produce a high-quality 3D-like image in the way the IMAX does, or Cinerama did.
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Most 3D games won't let you set the FOV to 180 degrees, since it's impossible using flat (pinhole?) projection that most of them use. This choice of projection is also why things look so distorted at the edges of the screen with a high FOV, and is why objects that are near you appear larger than objects in front of you, even when they're the same distance away, among other visual quirks. In order to show such a wide angle (approaching 180 degrees or above), you'd need to use a projection that's not limited to showing objects on one side of a plane, such as fisheye projection. This isn't normally done because it's technically simpler to do 3D rendering when straight lines in the world correspond to straight lines on the screen (that's the simplified explaination).
See this page for a visual comparison.
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