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Author Topic: Face scanner - Prototype  (Read 39783 times)

Mfranquelo

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Face scanner - Prototype
« on: December 11, 2013, 01:43:28 PM »
Dear all,

After many questions, doubts solved and problems addressed - Im very happy to share with you all my very first prototype of Stereophotogrammetry face scanner:  :)

- https://www.dropbox.com/sc/suy6fwejacnbn50/aSMR2CZQ4E -

--------------- Key features: -------------

* I really wanted it to be "cheap" although at the cost of not being totally instant (it takes 2 seconds to go from 40 degrees to 140 degrees (there are angle limitations for the body, security of the cameras etc)

* It is important that the subject doesnt move - for alignment purposes.

* The scanning is done with total darkness as of yet, every camera opens their shutter for 1/50, in between that time, the flashes are fired at 1/16intensity.

* The prototype has a inclinometer (acelerometer) sensor on the rotation axis (similar to the ones our mobile phones have to detect inclination. (its the blue box)

* When the inclinometer detects the programmed ? angle it sends the shutter signal to each of the cameras and flashes

---------- Details -----------

Pre-mirror up signals are sent so the camera's total shutter lag is decreased.

- Time between fully shutter mechanical operations is around 0,4 seconds. That is : The camera is not ready to shoot again until 0,4 seconds.
- Cameras are Canon 700d (i bought those ones because they had better FPS)
- Flashes are Yongnuo 560 iii
- Lenses are canon 1.8f 50mm
- The radius of the semi circumference is 80cm
- Distance between cameras is around 26cm

* For 6 programmed angles, the total shooting time is 2 seconds of scanning.
(shoots every 20 degrees) 6 times. That is : 36 photos. (Maybe i?ll add two more cameras), but no more.


------------------------------------- ISSUES ------------------------------------------------


In my opinion, the fact that the flashes are moving relative to the subject is not very good for feature detection

Subject movement is a problem of course, but if i do the movement within 2 seconds and the subject tries to stand still, alignment is done correctly.


-----------


I Would really love to read opinions, thoughts or critics of course!  :)
* I?ll keep this post up to date with any new tests, problems or results so that we can all share our experiences!

https://www.dropbox.com/sc/suy6fwejacnbn50/aSMR2CZQ4E
« Last Edit: December 11, 2013, 08:34:43 PM by Mfranquelo »

emage

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Re: Face scanner - Prototype
« Reply #1 on: December 11, 2013, 02:44:05 PM »
Nice idea!

i would love to see how well this setup performs.
really creative approach.

will be following this thread

Mr_Curious

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Re: Face scanner - Prototype
« Reply #2 on: December 11, 2013, 02:54:08 PM »
Very innovative concept - love it!

Keep up the great work.


Mfranquelo

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Re: Face scanner - Prototype
« Reply #3 on: December 11, 2013, 08:36:53 PM »
Emage, Mr_Curious Thank you!
I hope ill be able to post some tests tomorrow as well as some issues for sure! I just bought my photoscan license finally :)

Alexey, what do you think of this approach ? could you tell me any issues that the software could have with this system ?




Alexey Pasumansky

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Re: Face scanner - Prototype
« Reply #4 on: December 12, 2013, 02:55:08 PM »
Hello Manuel,

I think that the possible problems of such system you have already mentioned in your first post:
- slight movements of the person during scanning,
- change of the source of light position.
Best regards,
Alexey Pasumansky,
Agisoft LLC

Mfranquelo

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Re: Face scanner - Prototype
« Reply #5 on: December 12, 2013, 09:38:05 PM »
I promised some examples of my system, so here it goes :
(Those are very early tests, everything will be improved with noise projection)
Tell me what you think!


Mfranquelo

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Re: Face scanner - Prototype
« Reply #6 on: December 12, 2013, 09:40:55 PM »
Mesh is still a little bit noisy, i guess i need more corresponding points to be found, at the moment i have around 39k.


Exhale

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Re: Face scanner - Prototype
« Reply #7 on: December 12, 2013, 10:11:36 PM »
Good work, can u pls upload textured one as well.

Mfranquelo

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Re: Face scanner - Prototype
« Reply #8 on: December 13, 2013, 02:15:28 AM »
Okay, Ill post a few results (spraying paint on the subjects face) as well as texture rendering screenshot.



Mfranquelo

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Re: Face scanner - Prototype
« Reply #9 on: December 13, 2013, 05:34:13 PM »
Results are still too noisy... i need to sort that out.
I dont like Zbrush smoothing brush, a filter as someone had mentioned here would be of course better, (Noise should of course be sorted out by increasing the scans quality...)

---

Im getting like 45k points, is that too few ?
Maybe the quality between correspondances is not good enough ? what numbers should i aim for ?

Thank you in advance for your help!
« Last Edit: December 13, 2013, 05:52:52 PM by Mfranquelo »

Exhale

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Re: Face scanner - Prototype
« Reply #10 on: December 15, 2013, 01:59:37 PM »
Did you sort out the resulation issue?  :)

Mfranquelo

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Re: Face scanner - Prototype
« Reply #11 on: December 15, 2013, 03:03:45 PM »
Not yet  :(, ill try to fix the illumination source so it doesnt move relative to the subject, that may increase geometric reconstruction quality.

Also ill try Meshlab's noise filtering options.
 

FoodMan

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Re: Face scanner - Prototype
« Reply #12 on: December 15, 2013, 03:26:06 PM »
right !... the lights should never move...

andy_s

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Re: Face scanner - Prototype
« Reply #13 on: December 15, 2013, 08:30:08 PM »
- Flashes are Yongnuo 560 iii

Hi Mfranquelo, thanks for sharing this - very interesting.

I hadn't really considered this type of flash before - but my memory is that light production period is around 40 ┬Ásec ?

Might you describe how you synchronise them ?
What sort of calculation did you do to decide on quantity ?


Does anybody know if the Yongnuo fit the spiffy gear projector [previously posted somewhere on the forum as http://www.the-digital-picture.com/Reviews/Spiffy-Gear-Light-Blaster.aspx] ?

Does anybody have an idea [to share] how many spiffy's might be needed for whole body capture?

Apologies for vagueness [lazy Sunday post]

Mfranquelo

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Re: Face scanner - Prototype
« Reply #14 on: December 16, 2013, 12:29:43 PM »
FoodMan thats right, i didn?t know it was that important even with the light changing in a very diffuse way :(

andy_s Yongnuo's are amazing flashes that cost like 80 euro (where i live at least),  they have more or less the same features as the so-expensive Canon 580 ex ii (This yongnuo flash is manual, however i dont care, for my needs)

I?ve sincronized them creating a custom cable and - a microcontroller was programmed to fire the flashes by closing the circuit exactly after the median shutter lag of my 6 cameras which is around 79ms + security time. This is done on total darkness, so the photos are mathematically syncronized.

I was about to test x2 light blaster + noise semi transparent slide, however i dont have the budget do this yet, so im faking the noise projection by painting little dots on my subjects face for the tests.
I can tell you the results when i have them. I guess that 3 light projects would be needed , or maybe two at 45 degrees to the face.
- For sure it fits, the yongnuo has the same shape as canon speedlites.

Quantity was just a guess, i kept adding flashes until i got a decent ratio between diffuse and intensity of light. Flash speed at 1/16 power was just more than enough for my needs. You could calculate light intesity fall off and reflectivity based on the flesh, but thats just a waste of time, its faster to test it.

Manuel.
« Last Edit: December 16, 2013, 12:33:34 PM by Mfranquelo »