bugBino - Bugs: bug #35106, shadow effect when using Dubois...

 
 

bug #35106: shadow effect when using Dubois anaglyph method

Submitted by:  S. Christian Collins <mrbumpy409>
Submitted on:  Sun 18 Dec 2011 06:04:30 PM UTC  
 
Severity: 3 - NormalStatus: Wont Fix
Privacy: PublicAssigned to: Martin Lambers <marlam>
Open/Closed: Closed

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Sat 28 Jan 2012 10:35:53 AM UTC, comment #5:

I re-read a mail discussion with Prof. Dubois that we had last February.

According to him, his method assumes linear RGB values, his matrices are designed for this case, and he applies them to linear RGB in his own programs. Therefore, Bino does this, too.

StereoPhotoMaker (and presumably AnaBuilder) apply the matrices to sRGB instead, which leads to different results.

Citing Prof. Dubois: "[...] in principle, all the matrices are designed for linear RGB, but still work reasonably on gamma-corrected sRGB. I guess you can try them all and use the one you like best."

You can switch Bino to apply the matrices to sRGB instead of linear RGB by changing video_output_render.fs.glsl. This leads to almost the same results as the StereoPhotoMaker and AnaBuilder images you sent.

However, I still prefer to keep the matrices as originally intended, even if I can see the ghosting artefacts you described. If we change this, I fear this will lead to quality loss of a different kind in other situations. Poor color quality is unavoidable with anaglyph glasses, but at least the current method has a solid background.

I'm closing this bug, but please feel free to re-open it or send feedback if you disagree.

Best regards,
Martin

Martin Lambers <marlam>
Project AdministratorIn charge of this item.
Sat 07 Jan 2012 11:36:23 PM UTC, comment #4:

Whoops, I forgot to turn off the brightness color adjustment (+0.03) in Bino before taking the screenshot. Attached is the corrected image pack.

(file #24762)

S. Christian Collins <mrbumpy409>
Sat 07 Jan 2012 09:37:00 PM UTC, comment #3:

Upon further testing, it seems that Bino's calculations for the Dubois algorithm may be a bit off. Dubois anaglyphs generated using other programs do not exhibit the "shadow ghosting" reported in this bug.

The attached archive contains a test pattern rendered in Dubois anaglyph using StereoPhotoMaker, Anabuilder and Bino, along with the source image as a l/r full-width PNG.

The StereoPhotoMaker and Anabuilder-generated images are identical, whereas the Bino image's colors differ. Loading each image as a layer into GIMP and toggling the visibility while wearing anaglyph glasses shows the difference quite clearly. Near the bottom of the 3rd-5th stripes of each color zone is where you can see the shadow ghosting most clearly.

(file #24761)

S. Christian Collins <mrbumpy409>
Sat 07 Jan 2012 04:35:07 PM UTC, comment #2:

As I understand it, the Stereoscopic Player's "optimized anaglyph" mode is a heuristic that may or may not work - it looks a little fishy to me, but I never actually tried it since I never used the player.

The Dubois method has a solid foundation: it is based on measurements of a specific pair of anaglyph glasses and a specific LCD monitor, and uses an optimization to reduce the amount of artefacts expected with this setup to a minimum.

While the theory of the method is very nice, it only works perfectly for the glasses and the monitor that were measured. The numbers I use in Bino come from E. Dubois himself; he measured high-quality anaglyph glasses and a CRT monitor about which I don't have any information (but I assume he did some color calibration).

So, how well Dubois' method works depends on how similar a particular setup is to the one that he measured.

I don't think we can improve the current situation; measuring a different setup would just result in different problems. Maybe it would help to measure a perfectly calibrated LCD, but I don't have the equipment.

Martin

Martin Lambers <marlam>
Project AdministratorIn charge of this item.
Thu 22 Dec 2011 06:03:20 PM UTC, comment #1:

After playing with this some more, I've noticed that the reduced left eye ghosting + right eye shadow effect actually helps the eye focus on the 3d objects better about 90% of the time. Every once in a while I notice the shadowing effect around high-contrast edges, but the overall clarity of depth is definitely better using Bino's Dubois method.

So... maybe this isn't a bug, but a deliberate compromise by the programmer. However, perhaps it can still be fine-tuned? I will leave this bug open in case this method can still be improved to reduce the right-eye shadow effect.

I will be happy to do any testing as I have multiple test displays with good color/gamma calibration.

S. Christian Collins <mrbumpy409>
Sun 18 Dec 2011 06:04:30 PM UTC, original submission:

Ghosting (crosstalk) in anaglyph mode is often caused by the glasses' filters not perfectly matching the screen's color output. As a result, I have very slight ghosting when using the half- or full-color anaglyph modes, as would be expected.

However, when using the Dubois method, the ghosting in my left eye is slightly reduced, while the ghosting in my right eye appears extra dark, creating a sort of shadow effect. This happens with both the red/cyan and green/magenta modes (haven't tested the others, as I don't have the required glasses).

This effect can be easily observed using the attached image file.
1. Load the image file into Bino.
2. Set the input to "Left/right, half width", and select the appropriate half-color anaglyph mode for your glasses.
3. Focus on the bottom-right circle. Observe the amount of ghosting when looking through only your left eye, then your right.
4. Switch to Dubois rendering. Look through only the left eye. In my case, the ghosting is now reduced for the left eye. Now look through only the right eye. In my case (on two PCs, one CRT, one LCD), the ghost has now gone from slightly light to slightly dark. This dark shadow for a ghost is very noticeable, and is distracting when it happens in videos.

To compare, I tried using Stereoscopic Player's (http://3dtv.at/Index_en.aspx) optimized anaglyph mode, and this type of shadow ghosting does not occur.

A note about my setup: I have meticulously tweaked my monitor for perfect color, and it is currently set at a gamma of 2.2. Ghosting in both red/cyan and green/magenta modes is minimal. My red/cyan glasses are from the Spy Kids 3D movie, and my green/magenta glasses are from Coraline--both the cardboard kind. I am using Bino on Kubuntu 11.10.

S. Christian Collins <mrbumpy409>

 

(Note: upload size limit is set to 16384 kB, after insertion of the required escape characters.)

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Attached Files
file #24762:  ghosting-test-C3-files_fixed.tar.gz added by mrbumpy409 (525KiB - application/x-gzip - corrected ghosting test C3 files)
file #24761:  ghosting test C3 files.tar.gz added by mrbumpy409 (527KiB - application/x-gzip - Images for comparing Dubois anaglyph ghosting)
file #24624:  ghosting test B.png added by mrbumpy409 (11KiB - image/png - Image for testing crosstalk)

 

Depends on the following items: None found

Items that depend on this one: None found

 

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  • -unavailable- added by marlam (Posted a comment)
  • -unavailable- added by mrbumpy409 (Submitted the item)
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    Follow 6 latest changes.

    Date Changed By Updated Field Previous Value => Replaced By
    Sat 28 Jan 2012 10:35:53 AM UTCmarlamOpen/ClosedOpen=>Closed
    Sat 07 Jan 2012 11:36:23 PM UTCmrbumpy409Attached File-=>Added ghosting-test-C3-files_fixed.tar.gz, #24762
    Sat 07 Jan 2012 09:37:00 PM UTCmrbumpy409Attached File-=>Added ghosting test C3 files.tar.gz, #24761
    Sat 07 Jan 2012 04:35:07 PM UTCmarlamStatusNone=>Wont Fix
      Assigned toNone=>marlam
    Sun 18 Dec 2011 06:04:30 PM UTCmrbumpy409Attached File-=>Added ghosting test B.png, #24624

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