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Comment by maxst | Hacker News Reader

So many algorithms insist on using "single RGB camera" approach, when it would be much more practical to use 2 cameras.

The power is the existing giant corpus of video. When I'm in front of a computer I'm going to run this up against the dancing of James Brown and Michael Jackson. Should be interesting.

Maybe an Olympic gymnast as well.

Practical for an algorithm implementer, maybe - deeply impractical for real-world use. Stereo cameras are rare and nontrivial (you have to synchronize shutters). Monocular algorithms can be applied to the millions of hours of existing footage, or used with the billions of cameras, smartphones, robots, drones, and fancy doorbells that already exist right now.

For “slow” moving object like human body, does synchronised shutter matters that much and if so , is there any tricks to compensate it if synchronisation is not possible?

You can do reasonable software sync with identical cameras and threading - it gets you to within a few milliseconds.

Even for slow objects it's a problem because being a few pixels off might make the difference between matching and not.

There are dozens of 360 cameras on the market, so I think shutters synchronization is not that difficult to implement.

But 360° cams try to do something entirely different than, say a kinect.

I would be surprised if all 360° cameras had synchronized shutters.

360 cameras produce spherical panoramas from a single point and would not help capture of a person on a stage over a regular camera.

If you can calibrate the time-delay between the two cameras, can you not just interpolate one or the other signal backward or forward in time so that it aligns with the other? (By "interpolation", here, I mean the sort of thing the Oculus does on the display side, generating frames "between" frames, to smooth motion during head rotation. Take one real frame from one camera, and build an interpolated frame between two real frames from the other camera to match it.)

Only for near-field. Further out than roughly an arm-span, your brain itself doesn't use binocular vision for 3D estimation because there's not that much information in the parallax.

do you have a source for that? because my source: one closed eye, tells me very clearly i do use binocular vision for 3d - 3d being how far something is.

you don't need 'much' information. you know the distance between the eyes, and then you have the 2 lines from each eye to the object. that's called a triangle. do you know how to calculate the height of a triangle? because that's your distance.

If you read my comment again, possibly all of it this time, you'll see that I'm not saying that we don't have or use binocular vision. I'm saying that there's a limit to how far out it's useful. That means adding a second camera is only going to be useful for a small number of tasks.

Messing about with triangles is called convergence. The accuracy falls off quite quickly with distance, and it's completely useless out past about 10m. Your brain has much better sources of depth cues before that point.

There are at least another 12 mechanisms humans use for depth perception, only one (arguably two) of which uses both eyes. I'll let you do the googling.

i don't need to 'google' what closing one eye does. that's the whole point of my comment. you claim it's unreasonable when people use their eyes for basic information. i say having to google what your own eyes tell you is what is unreasonable.

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