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Our structured light scanning rig

Problems, solutions and discussion about scanning with a video projector and stripe patterns.

Re: Our structured light scanning rig

Postby Kirch » Sat Oct 31, 2009 11:29 pm

Hey Maxem,
That is very very helpful to me. Thanks for the info. I was walking the aisles of Best Buy yesterday looking at the projectors. First time I've ever looked at these devices to tell you the truth. My budget is keeping me from pumping in more dinero for my Davidian "experiments"= (playtime) at the moment. I'm following the results of you and Moe here closely, though, so keep on posting! :D

Is the manner with which you "extract" the images something that runs inside of david or are you running the vid through some other system? As Moe mentioned above, he has some sort of a triggering device for his camera and projector. It sounds like you are running a video and procesing your 12 images from there somehow. Is this correct?

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Re: Our structured light scanning rig

Postby maxem » Sun Nov 01, 2009 12:59 am

Hey Moe,
Thanks! Yes I think the problem is with multiple scan lines is my projector. The 3 LCD's (R,G,B) are not aligned, it is old and has taken a beating over the years.
This is a gray-code (pattern 07) left side is horizontal pattern and you can see purple edge on top and yellow/green on bottom of black. Then i made vertical patterns you see to the right, but here is blue on left and red on right of each black line.

To see what this causes i played with all patterns and combinations in photoshop to see what David sees
***Now i'm only guessing this is how it works from what i can see with photoshop:

If you only load the first 6 pics from your scan you will see all scan lines moving at once. Then David uses the last gray-code patterns to displayed them in the right order to simulate one line moving down entire screen. Scan data to the right shows those momentary flashes of second line which ruins the good data.
My line flashes are because the projector is not making a sharp edge to the gray-code patterns because of the color bleeding on edges of black lines. I noticed it because the flashes happen almost every complete sin wave. My solution is to photoshop down the brightness all the way on just that shade of purple and yellow/green, this will not work on an object with those same colors. Below is what the hand images with +2 close up filter looked like before i darkened the bleeding color from projector:

Long story short I am ordering a DLP projector! I've owned that panasonic LCD projector for years and have gotten my mileage out of it several times...

Moe I have been finding that generating my own "all black" first image from the fringe patterns is giving me interesting results, its kinda the reverse of editing all the other images as you suggested before (which has helped me get more out of scans, thanks!). I don't know if this black image creation thing works or it my be the faulty projector throwing me off, a few more tests and i'll have some info.

@ Kahlid Thank you. just read this post from beginning info is there, or the end of this other one:

@Karl I am currently taking still photos with a DSLR, I play video slideshow out to projector of all the slides and I have a remote shutter button for my canon camera. all i do is let the slideshow loop displaying each pattern for 1 second, just enough for me to snap photo of each one so i get a full scan (all 12 photos) in 12 seconds. I think Moe has some really nifty ardurino board and programing allowing him to shoot his canon camera at its maximum frames per second to get it in like 4secs or something.
What I plan to do is play out a video where each pattern is displayed for 3-4 frames 30fps and my canon(t1i) can also record 20fps full HD 1920x1080p. This should give me all 12 photos in 1.5sec, the problem with this method is i have to use a seperate video editing program to extract the 12 good frames and save them out as still images, also i get much higher resolution with the regular camera photos than HD video recording.
Last edited by maxem on Sat Jan 02, 2010 7:43 pm, edited 3 times in total.
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Re: Our structured light scanning rig

Postby Moe » Sun Nov 01, 2009 6:26 pm

Hey Maxem,

thanks a lot for your detailed explanation. Just some ideas: the color fringes around contrasting edges on the projection might have another origin than misaligned panels: In cameras there's a very similar phenomenon called "chromatic aberration" which means that a lens bends different wavelengths of light (=> different colors) differently, resulting in color fringing. You'll see it in almost every lens (except maybe those gazillion-€ expensive Zeiss Primes...).

I as well suppose that the gray-coded patterns are there to determine which line goes where but the whole point in using gray-coded patterns over simple binary coded patterns is in their robustness concerning pixels around their edges... I'm a bit confused... Any comments from the developers side?

Anyways - thanks again. Gotta think what to improve next :)
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Re: Our structured light scanning rig

Postby maxem » Sun Nov 01, 2009 9:47 pm


Sorry i wrote "grayscale" patterns and meant "gray code" patterns oops!
I mean the last 6 patterns of the sequence(patterns 06-11) I will edit this in previous post.

The color fringing on the gray CODE patterns is definitely visible to your eye. plus this is how my full black screen looks:
Projector Black-3995.jpg

This is not dust on the lens but inside on LCD's
While I'm waiting for my new DLP projector to arrive have you any tricks to deal with dark hair that makes holes in mesh? I have read here that people brush on white powder for laser scans?
Anything to prop up subject to keep them still while scanning?

I hope the guys with the brains behind this are just to busy to read this because they're working on making structured light a fulltime part of David. haha

I have one trick for you that you may be doing already.
When playing with tweaking photo exposures i don't wait for capturing entire scan. I simply load the first six photos (00-06). Then you see all scanlines at once like a waterfall over your subject, but this is much faster to preview the scanlines to see if you have gone to far with tweaking contrast levels. When lines look strong then i do a scan with all 12 photos.
scanline waterfall.jpg

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Re: Our structured light scanning rig

Postby maxem » Sun Nov 01, 2009 10:16 pm

here is something i have found too...
When you shoot first all black photo it is much darker than what is supposed to be black in the rest of the photos so i make my own first "all black" photo which is closer to the black in the pattern photos.
Below is scan with untouched camera all black photo used:
original black frame.jpg

In photoshop i open all black and all white photo
then copy all white photo and paste on top of all black.
Then change layer blending mode from "normal" to "linear light" and drop the opacity down to 40% or whatever makes it look close to what is supposed to be black in the rest of the pattern photos.
Below left is photoshop'd black frame and results right:
New Black Frame.jpg

Nothing else is changed I am only replacing the 1st black photo. I think this works because when patterns are projected the white light bounces around and blacks aren't fully black, so this is compensating for that i guess, dunno...
but atleast the scan line is cleaner:
original black photo results.jpg

what i am proposing here is that the first frame should not be all black but a dark gray this way no photoshoping...
I know i'm just shooting in the dark here with these tests but anything to help progress structured light, if its reliable it could be a great help to me.
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Re: Our structured light scanning rig

Postby Moe » Wed Nov 11, 2009 5:51 pm

Alright ladies and gentlemen,

after having held an intermediate presentation on 3D-Scanning today here's one of the demo images that've been done during last week. Came out pretty well. Thanks to Robert again for providing a smoothly shaved head.

Mesh consists of 16 merged scans. Has been smoothed in C4D and separate texture shot was camera mapped onto mesh. Created additional detail by bump-mapping a filtered version of the texture photo. Rendered using HDRI & GI.

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Re: Our structured light scanning rig

Postby Khalid Khattak » Wed Nov 11, 2009 6:06 pm

Very Nice Head;) Why He closed his eyes?..Is he meditating?... BTW nice scan results..Kepp it up and give money to Robert for keep shaving..But I will suggest to apply some water based paint or Talcum Powder on his shiny head;)
PC: Dell Inspiron i3, 2.27GHz,4GB RAM,64 bit windows 7
David CCD Mono USB
David 5mW Green line laser
3D LED Mini Projector 250lumens, Native 1024x600
Khalid Khattak
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Postby hal » Wed Nov 11, 2009 6:13 pm

Really impressive result. And what incredible texturing: perfect work!
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Re: Our structured light scanning rig

Postby RAYA » Thu Nov 12, 2009 3:01 pm

Hi Moe

Nice work

What about calibration panels ?

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