MSU Graphics & Media Lab Report #6 on stereo films quality assessment
One of the common issues with stereo 3D (S3D) movies is the presence of stereo-window violations. A stereo-window violation can be defined as a contradiction between two different depth cues where an object on the side of the image is partly hidden by a border of the frame but, owing to its parallax, appears closer than the border (Image #1). As with other contradictions, this situation can cause serious discomfort because it almost never occurs under viewing conditions in a real environment. However, it often receives surprisingly little attention during both production and screening of S3D movies. The Graphics & Media Lab CMC of Lomonosov Moscow State University decided to investigate this problem.
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In most cases the stereo-window violation issue can be fixed by means of the floating-window technique. A floating window is simply a black stripe added to the edge of one of the views to cover window-violating content (Image #2). A lot of different strategies can be employed in using this technique, including static, dynamic, slant or even curved floating windows (Images #3-5)
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The sixth report is dedicated to the analysis of stereo-window violation issue and use of floating windows in various S3D movies. It addresses 10 different S3D films, both natively captured and post-converted:
- The Amazing Spiderman
- The Three Musketeers
- Pirates of the Caribbean: On Stranger Tides
- Dolphin Tale
- Drive Angry
- The Avengers
- John Carter
- G-Force
- Abraham Lincoln: Vampire Hunter
- Clash of the Titans
The report presents per-frame charts that enable the analysis of floating window behaviour with respect to disparity of the closest object near the edge of the frame (Image #6). The charts are accompanied by visualizations of the most noticeable window violations.
Image #6: Example of a per-frame analysis chart
The report also presents an overall comparison of films in terms of quality of stereo window violation handling.
One may notice that more recent movies tend to have better stereo-window violation handling (Image #7)
Image #7: Stereo Window Violation vs. Release Date
Naturally, films with heavy use of floating windows tend to have less stereo-window violations. However, some films achieve low stereo-window violation number with virtually no floating windows across the whole film (Image #8)
Image #8: Stereo Window Violation vs. Floating Window Usage Intensity
This fact can be explained by looking at the average disparities of the closest object near the edge of the screen (Image #9). In fact, The Three Musketeers has the highest average positive disparity value, indicating that, indeed, floating windows are not required to achieve low stereo window violation level in this film.
Image #9: Stereo Window Violation vs. Closest Object Disparity
Acknowledgements
We would like to thank the following people for providing valuable comments, opinions and feedback, which helped to improve this report:
- Marcus Alexander, Stereoscopic Designer, 3D Producer
- Olivier Cahen, Stereoscopic Consultant, Author
- Ross Copeland, Online Editor / Stereographer & Colourist, Post-Production Consultant
- Lluis Dubreuil, Stereographer, Stereoscopic Consultant
- Markus Lanxinger, Stereographer, Stereoscopic Supervisor
- Enrico Perei, On-Set/Post Production Stereographer, VFX Supervisor
- Fabien Remblier, S3D and 4K Director, Stereographer, Producer
- Wesley Sewell, Stereographic Supervisor
- Thomas Villepoux, Director, Stereographer
A key motive of our reports is to improve the stereo quality and therefore to reduce eyestrain and headache. The Graphics & Media Lab hopes that a high 3D video quality would contribute to a continually increasing number of people, leaving the modern theaters without annoyance and with good impressions from the image quality and storytelling.
We are always interested in feedback from professionals in film-production industry. We have already collaborated with more than 20 stereographers who provided us valuable comments which were inserted in our reports. If you would like to participate in the next reports, please feel free to contact us: 3dmovietest@graphics.cs.msu.ru.
Reports overview
Stereo-analysis project description
Contacts
For questions and proposition please contact us 3dmovietest@graphics.cs.msu.ru
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