Trimensional: 3D Scanner for iPhone • Hacker News Board

Re: Trimensional: 3D Scanner for iPhone

#11

Post by closure » Thu, Jan 06, 2011, 1:52 PM UTC

GrantS wrote: post #6

tobtoh wrote: post #4

Cool app. But I have a pet peeve with information pages that only provide video as a description. Whilst I understand that especially for an app like this, the best 'information' is to demonstrate how it works via a video, it doesn't help people a. just want to get a quick one line explanation of what your app does and/or b. can't watch the video at the time (slow connection, work restriction etc). If I hadn't been a…

Thanks for the feedback. I was expecting to have this weekend to pull everything together but Apple approved the app in 2 days (which is great, but 5x faster than for my previous submissions).

The first question that comes to mind for me is: Is it possible to export the generated mesh that is shown in the stills?

Re: Trimensional: 3D Scanner for iPhone

#12

Post by motters » Thu, Jan 06, 2011, 1:58 PM UTC

This is a shape from shading approach, which will only work if you're in the dark, with the phone as the only illumination source. If white dots are shown in different places on the screen, and assuming the phone and subject don't move during the process, surface normals can be computed from the resulting images, and once you have the normals then the shape can be approximated. Normals can be found by calculating the angle of maximum reflectance for each pixel for a series of images under different illuminations.

See this Google video for a similar technique. http://www.youtube.com/watch?v=rxNg-tXPPWc

Re: Trimensional: 3D Scanner for iPhone

#13

Post by GrantS » Thu, Jan 06, 2011, 2:04 PM UTC

closure wrote: post #11

GrantS wrote: post #6

Earlier quoted context omitted.

Thanks for the feedback. I was expecting to have this weekend to pull everything together but Apple approved the app in 2 days (which is great, but 5x faster than for my previous submissions).

The first question that comes to mind for me is: Is it possible to export the generated mesh that is shown in the stills?

Good question. Version 1.0 only saves/emails images, but trading 3D scans and exporting the raw mesh is certainly on the feature list for future versions.

Re: Trimensional: 3D Scanner for iPhone

#14

Post by lliiffee » Thu, Jan 06, 2011, 2:13 PM UTC

iwwr wrote: post #5

lliiffee wrote: post #3

Looks like it just uses the reflected intensity to estimate the depth, then pastes the original colormap on top of that? Incredibly clever and simple hack.

Can the iphone modulate the intensity of its light via software?

It looks like it is just sending a total blank white screen while it takes a picture. Sure you can change the intensity-- use a gray pixel instead of a white one.

Re: Trimensional: 3D Scanner for iPhone

#15

Post by [deleted] » Thu, Jan 06, 2011, 2:19 PM UTC

ericb wrote: post #9

The fact that this only works in the dark made me wonder, how much of what the Kinect does could be possible on an iPhone, and what would be needed to get there? 2 Cameras? What else?

[deleted]

Re: Trimensional: 3D Scanner for iPhone

#16

Post by motters » Thu, Jan 06, 2011, 2:24 PM UTC

ericb wrote: post #9

The fact that this only works in the dark made me wonder, how much of what the Kinect does could be possible on an iPhone, and what would be needed to get there? 2 Cameras? What else?

If the phone had two cameras spaced some distance apart then you could use stereo vision algorithms to get a similar result. Maybe it would be possible to put an infrared laser on a phone, similar to the Kinect, but I expect that power consumption would become an issue (although if it's only in a momentary blast it might be feasible).

There are other possible methods, such as the "photo popup" created at CMU some years ago, but these rely heavily upon "dodgy heuristics" and often fail to give a good result.

Re: Trimensional: 3D Scanner for iPhone

#17

Post by dsherhrt » Thu, Jan 06, 2011, 2:29 PM UTC

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Re: Trimensional: 3D Scanner for iPhone

#18

Post by magicseth » Thu, Jan 06, 2011, 3:42 PM UTC

GrantS wrote: post #13

closure wrote: post #11

Earlier quoted context omitted.

The first question that comes to mind for me is: Is it possible to export the generated mesh that is shown in the stills?

Good question. Version 1.0 only saves/emails images, but trading 3D scans and exporting the raw mesh is certainly on the feature list for future versions.

Might I suggest using the Bump API to share scans?

Re: Trimensional: 3D Scanner for iPhone

#19

Post by magicseth » Thu, Jan 06, 2011, 3:45 PM UTC

I tried it this morning in the pitch black. It worked pretty well. The effect was mostly comical with some distortion. The most interesting aspect is how people are taking all these things that at first pass would be considered "impossible," applying some ingenuity and hard work to them, and pushing the limits of this technology.

Re: Trimensional: 3D Scanner for iPhone

#20

Post by sbierwagen » Thu, Jan 06, 2011, 4:22 PM UTC

ericb wrote: post #9

The fact that this only works in the dark made me wonder, how much of what the Kinect does could be possible on an iPhone, and what would be needed to get there? 2 Cameras? What else?

If your subject doesn't move, two cameras can be approximated by taking two pictures a set distance apart.[1]

Also note that the method used by this app is very short ranged, and uses the LCD's backlight while it's imaging, so there's zero feedback, making any kind of interactive application impossible.

1: There are third party accessories to make this easy and repeatable, built with varying levels of quality. Here's a fairly cheap one, circa 2003: http://www.dansdata.com/photo3d.htm