Janne Taponen Screen Specic Stereoscopic 3D Content

Transcription

1 Janne Taponen Screen Specic Stereoscopic 3D Content Bachelor of Science Thesis Examiner: Konsta Koppinen

2 II ABSTRACT Tampere University Of Technology Bachelor's Degree Programme in Computer Science Author: Janne Taponen Bachelor of Science Thesis, 22 pages, 2 Appendix pages December 2010 Major: Signal Processing and Multimedia Examiner: Konsta Koppinen Keywords: Stereoscopic Video, 3D Video, Screen specic content This thesis studies the eects of scaling stereoscopic 3D content to t dierent displays and how to maintain a proper depth perception. If stereoscopic 3D content is scaled to t a dierent display device the content will appear to be skewed along the z-axis due to the non-linear nature of interocular distance. For this thesis, experiments were done to understand and illustrate the eects of this scaling. This thesis also briey reviews the most recent methods for non-linearly correcting interocular distance to maintain correct depth for the scenes.

3 III CONTENTS 1. Introduction Human visual system Projection and viewing Polarization method Interference Filtering method Eclipse method Autostereoscopic displays Screen size problem and adaptive parallax Resolution specic content Fixing parallax in post-production Automatic disparity correction on an end user device Experiments Tools Experiments Conclusions References A.Appendix

4 IV TERMS AND SYMBOLS IOD NPP LC-Glasses Binocular disparity Convergence Divergence Cardboarding Hyperstereoscopy Negative parallax Positive parallax Interocular distance - Distance between the eyes. 64mm is considered to be the average distance for most people. Native pixel parallax - How large horizontal parallax between views is possible. Liquid Crystal Glasses - Shutter glasses that have electronic liquid crystal shutters. The dierence in the images projected onto the back of the eye (and then onto the visual cortex) because the eyes are separated horizontally by the interocular distance.[1] Movement of eyes towards each other to face the focal point. Movement of eyes away from each other and not converging to a mutual focal point. Artifact from downscaling stereoscopic content that makes the depth appear skewed. Artifact from upscaling stereoscopic content that makes furthest objects appear beyond innity, thus leading the eyes to diverge. The objects appear to be coming out from the display The objects appear to be behind the display

5 1 1. INTRODUCTION Advances in lm making over the recent years, the transformation from standard 35mm lm into the new digital camera systems and possibilities to generate complex visual eects using computers has brought 3D back to mainstream cinema. 3D versions of the biggest blockbusters such as Avatar and Shrek Forever After, have become some of the highest-grossing lms of all time. The growing popularity of 3D has lead studios to release most of their movies also as 3D versions. This has meant that most of the theaters are converting their existing equipment to have 3D capabilities. As the past has shown, when something is shown in theaters it will eventually nd its way into normal consumer products and this transformation is starting to show already. Major consumer electronics companies such as Sony, Panasonic and Samsung are all releasing consumer 3D displays and 3D capable players that employ various means of displaying stereoscopic imagery. More aordable consumer devices means that it's not going to be long before you're able to view 3D content on your laptop or on a mobile device such as a mobile phone. When the sizes of displays on the devices range from a 50" at-screen TV to a mobile phone with a 4" display, this introduces a completely new problem that doesn't exist to this extent with normal 2D content. When stereoscopic 3D content is produced for a specic resolution, usually a cinema presentation of a very high resolution up to 4K (4096 x 3072pixels) and screen sizes up to 30m wide, and this content is later downscaled to t the resolution and display of a mobile phone, it is no longer as attractive visually, due to distortions and artifacts caused by the downscaling. Downscaling causes many dierent issues with the content, but this thesis focuses solely on how it aects the perception of depth. The perceptual depth is only valid on the display and resolution size for which the content was originally created. When the content is resized to t other screens it will appear to be skewed along the z-axis.

6 2 2. HUMAN VISUAL SYSTEM Creating stereoscopic imagery can be simply thought of fooling the human visual system, but because of the level of sophistication our visual system operates at it is extremely important to understand what our eyes are perceiving. Our eyes are generally looking for cues to identify objects, their sizes, relations, positions in scenes, detail, lighting, shadows and occlusion. All of these cues are present in 2D imagery, however the introduction of depth generates additional cues for our eyes to perceive and, if any of these are even slightly o, it generally results in unnatural and not believable 3D imagery. The additional cues that 3D imagery brings are binocular disparity, accommodation and convergence. Binocular disparity is generally considered to be the main visual cue for most people [1]. Parallax or the horizontal dierence between the views, causes the imagery to appear to have a certain depth. This can be called either positive or negative parallax. Positive parallax means that objects are perceived to be behind the screen or zero parallax plane, and objects with negative parallax to appear in front of the zero parallax plane. These are illustrated in gure 2.1. The easiest way to understand convergence and accommodation is to think of a camera. In order to take a good photo of any particular scene, the camera needs to be pointed at the scene and then focused appropriately. The same also applies for the human visual system, our eyes need to rotate so they're facing the focal point of the scene and then the lens for each eye needs to be adjusted accordingly so the scene is in focus. These two steps for the human visual system are called convergence and accommodation respectively. As stereoscopic viewing causes more eye-strain, only a small region between the positive and negative parallax planes is usable for presenting objects. Extreme popout eects that were made using larger than normal negative parallax were extremely popular in the late 90s when the lm studios tried to make 3D lms more popular. These extreme eects are known to cause a lot of eye-strain because the comfortable level of parallax is exceeded. Modern 3D content tends to be designed to pop out less in order to make it possible to view feature length lms comfortably without experiencing eye-strain or nausea. [2]

7 2. Human visual system 3 Figure 2.1: Positive and negative parallaxes illustrated

8 4 3. PROJECTION AND VIEWING There are as many ways to view and display stereoscopic imagery as there is to generate it. The purpose of this chapter is to outline the most common systems and briey look at the advantages and disadvantages of each system. 3.1 Polarization method Polarization systems utilize dierent polarizations to distinguish between left and right images. Both linear or circular polarizations can be used to produce a stereoscopic image, although circular polarization is usually used because of its advantages over linear polarization. Circular polarization enables a viewer to tilt and move their head without disturbing the perception of depth. In polarization systems the picture is projected on to a specially coated silver screen, as reections from non-metallic surfaces destroys the polarization of the light. This allows for the usage of relatively inexpensive passive glasses that only have a dierent polarization lter for each eye. Projectors in polarization systems have usually either a lter that can change the polarity or a special lens assembly that does both the projection and the polarity changing. These systems only need one projector to project the image on to the screen since the images are alternated rather than interlaced. Polarization systems are still the most common 3D projection systems in theaters, but due to the recent boom in consumer electronics and the conversion of existing cinemas to have 3D capabilities, systems based on other methods are surpassing it. RealD Currently the most widely used technology based on polarization is RealD Inc's RealD Cinema. RealD Cinema uses passive glasses and circularly polarized light from a projector that alternates polarization for the left and right eye using a electro-optical liquid crystal modulator called ZScreen. Frames are polarized using opposite polarization for both eyes; clockwise for the right eye and counterclockwise for the left eye. Like other systems based on polarization, RealD Cinema uses a rather expensive silver screen to maintain the polarization of light in the projected image. Frames in RealD Cinema systems are projected using a method titled "Triple Flash" where each frame is displayed three times for each eye, thus resulting in a considerably higher frame rate of 72fps/eye compared to the normal cinematic frame rate

9 3. Projection and viewing 5 of 24fps/eye. The triple ash system is used to help to reduce the eects of icker, ghosting and stuttering in fast horizontal camera movements. [3] Flicker is the same video artifact that was present in old black and white lms where it is possible to see black ashes between the frames. Flicker simply means that the refresh rate is too slow and the viewer notices the changing of frames. Flicker was an especially big problem with the older CRT monitors that used low refresh rates. In ghosting, the viewer sees a halo of the previous frame on top of the current frame, which makes the picture look unsharp. Stuttering means that the motion displayed on screen doesn't look continuous and uid. The eects of stuttering can be easily noticed when viewing videos captured with, for example, a mobile phone camera. These videos usually have a very slow frame rate which means that any fast motion in the videos doesn't look uid. MasterImage 3D MasterImage 3D is a stereoscopic viewing system developed by MasterImage LLC. Like RealD, MasterImage 3D utilizes alternating circular polarization to dierentiate between frames for the left and right eye. Rather than using an electronic optical lter MasterImage 3D system uses a large disc that is placed in front of the projector. This disc is divided into two halves from which one has clockwise and the other counterclockwise polarization. The disc is spun at 4320rpm which results in one frame being displayed three times, and so MasterImage 3D systems have the same frame rates as the RealD systems. MasterImage 3D has a few advantages over RealD, because the system is based on a rotating disc it has better brightness compared to RealD. MasterImage 3D also doesn't need special les to compensate for the light leakage between eyes. MasterImage 3D is a fairly new system in the eld of stereoscopic projection but it has been growing quickly and is now claimed to be the fastest growing digital 3D system in North America and Europe. [4] 3.2 Interference Filtering method Interference ltering technique or wavelength multiplex visualization is based on shifting light and transmitting it at a dierent wavelength to its original wavelength, while still preserving the original color gamut. Rather than using a normal color wheel that has only red, green and blue lters, the wavelength multiplex color wheel has an additional set of red, green and blue lters which enables the light passing through the additional set of lters to shift from its original wavelength. In wavelength multiplex systems this shift in the wavelength is used to separate left and right images, meaning a set of red, green and blue color for each eye is shifted to dierent parts of the spectrum. The glasses used in cinemas using interference

10 3. Projection and viewing 6 Figure 3.1: Wavelength multiplexing illustrated. Purple and orange areas represent dichroic lters for left and right eye respectively. A dichroic lter for each eye is zero everywhere else except around the area where the allowed frequencies for that eye are. This simply means it acts as a bandpass lter picking only specic frequencies. In wavelength multiplexing both left and right frames are multiplexed together and displayed simultaneously so lters like this are needed to separate the views. ltering have complementary lters to the ones found in the color wheel of the projector. Dichroic lters or interference lters that can lter a specic range of colors very accurately are used in the glasses to allow only specic wavelengths to enter each eye. These lters are then used in the glasses to lter out the other set of colors and only allow the set of red, green and blue that is correct for each eye to enter it. [6] Figure 3.1 illustrates this ltering procedure. Dolby 3D The Dolby 3D Digital Cinema system developed by Dolby Laboratories Inc. uses wavelength multiplex visualization to achieve its stereoscopic eect. Dolby 3D Cinema is built using standard Dolby components and Dolby Digital Cinema projector which retains the compatibility with 2D movies while still allowing inexpensive conversion to 3D by simply changing the projectors color wheel to a 3D color wheel with an additional set of red, green and blue lters. Cinemas using Dolby 3D and wavelength multiplexing can use their existing screen for projection since wavelength multiplexing doesn't need special silver screens to maintain the properties of the projected light. Projectors using wavelength multiplexing are able to show both the left and the right frames simultaneously, with richer and more realistic colors and a sharper image. [5, 6] 3.3 Eclipse method The eclipse method of showing 3D imagery has the same basic idea as the polarization system; projected frames are alternated. In the eclipse systems, rather than

11 3. Projection and viewing 7 needing to invest in relatively expensive specially coated screens, a normal screen can be used since the stereoscopic eect is achieved by blocking eyes using special liquid crystal shutter glasses or LC glasses. These glasses have shutters that are opened and closed in synchronization with the projector alternating the left and right frames. Eclipse method based systems only need an image source that's capable of displaying higher than normal frame rates and transmit the synchronization data either wirelessly or via a cable. Nearly all of the current consumer 3D displays use this method for showing stereoscopic images because the eclipse method only needs a transmitter to make sure the glasses are synchronized with the display and a panel capable of a high enough refresh rate. A major drawback in this 3D technology and why it's only slowly catching up is due to the expensive shutter glasses, with most models being hundreds of euros. These electronic glasses need to have shutters for blocking each eye and a receiver for receiving the synchronization data. The lens of each eye on the glasses contains a thin liquid crystal layer which can be used to block the view of the screen from the eye based on the timing signal sent by the video source. Since each eye can see the whole frame at a time without any ltering eclipse systems have more neutral colors and viewers are able to see the whole color spectrum. Because LC glasses have shutters this usually results in icker. Since the frames for eyes are alternated the viewer is actually perceiving only half of the actual refresh rate of the source video. This means that refresh rates of monitors and projectors need to be doubled to reduce icker. There are many manufacturers who are manufacturing LC glasses for home-viewing, including all the major consumer electronics companies such as Panasonic, Samsung and Sony. Other manufacturers like, XpanD 3D or Nvidia, are focusing on more specic marketing segments like cinema or PC. XpanD 3D is currently the most well known manufacturer of eclipse based cinema systems, with over 1000 cinemas using their LC glasses. 3.4 Autostereoscopic displays Autostereoscopic displays allow viewers to see stereoscopic images without the need for any special viewing aids such as shutter- or polarized glasses. There are many dierent types of autostereoscopic displays, such as parallax barrier, lenticular, volumetric and holographic. Due to limitations in each of the display technologies, the most used technologies employ either parallax barriers or lenticular lenses. Both the display types use optical elements added on top of the surface of the screen. These optical elements scatter the light emitted from the screen in a specic way where each of the eyes are receiving a dierent image thus resulting in a stereoscopic image. Because light is scattered or redirected to specic places this means that both of these screen types have very limited viewing regions where the stereoscopic image is visible. Images for autostereoscopic displays are usually interlaced and images for

12 3. Projection and viewing 8 left and right eye are alternating on every vertical pixel row. One of the biggest problems for these display types is the halving of the horizontal resolution due to the alternating rows, so either the number of horizontal pixels needs to be doubled in order to have the same resolution or the resolution of the source material needs to be halved. Lenticular Lenticular autostereoscopic displays usually have long sheets of narrow lenses layered on top of each vertical row of the display. The purpose of these lenticular lenses is to direct light from each vertical row in dierent directions. This generates the problem that only horizontal parallax information is visible which, in most cases, is enough to provide acceptable stereoscopic eect. However, it is also possible to have spherical lenses on top of each pixel, which allows a viewer to see both horizontally and vertically varying parallax. Although autostereoscopic displays with spherical lenses in theory provide a more realistic stereoscopic image, lenticular displays with long cylindrical lens arrays over vertical rows are still much more common. [7] Parallax Barrier Parallax barrier displays use the same principle as lenticular displays, but rather than having a layer of lenses on top of the screen, they have as the name illustrates, a barrier. The parallax barrier is a layer of narrow vertical slits that, when viewed from the correct distance, allows the viewer's eyes to see dierent vertical rows. This property is then used in similar fashion as in lenticular displays to show interlaced images where rows alternate showing a dierent image to each eye. Because parallax barrier uses slits rather than lenses to dierentiate the vertical rows it generates several problems such as: the viewer might be able to view under the slits neighbor, the viewer may experience repeating perspective when moving around and due to the nature of the slits, there's always some discontinuity or dark lines present in the image. [7]

13 9 4. SCREEN SIZE PROBLEM AND ADAPTIVE PARALLAX Despite recent technological advances stereoscopic content production and display are facing major issues, including limitations of the viewing devices, the considerable expertise needed to lm, direct and edit stereoscopic material, and the fact that the human visual system is extremely good in spotting even the smallest inconsistencies. All of these contribute to making the perceived depth eect of the stereoscopic content to either completely shatter or to be severely disrupted. While convergence can be accurately reproduced using modern display technology, most of the other depth cues cannot be reproduced in a way that the generated content looks natural. Depth cues like eye accommodation are very hard to recreate using only a at projection surface like a TV or a mobile phone[8]. The huge variety of dierent end user devices and their dierent specications create another major problem in making stereoscopic content look natural. 4.1 Resolution specic content The introduction of stereoscopic 3D has brought new problems for creating natural looking content for dierent end user devices. Generally stereoscopic content can be considered display size and resolution dependent. The created content will only look as originally intended on end user devices that have the same display size and resolution as the parameters to which it was optimized upon creation. Whether stereoscopic content is created using 3D animation software or lming on location, these parameters including interocular distance, camera baseline distance, desired positive and negative disparity ranges along with the desired display device and its properties like resolution and size, need to be decided before the actual lming is started because they play important role in how natural the nal content will look. All of these parameters need to be taken into account before starting to produce the content. None of these parameters can be naturally adjusted after the initial creation of the content, making stereoscopic content production extremely inexible compared to the standard content production. Now the research on stereoscopic content creation is more and more focused on making the content independent to the display device specications and to avoid artifacts that result from scaling such as cardboarding or hyperstereoscopy.

14 4. Screen size problem and adaptive parallax 10 Figure 4.1: Hyperstereoscopy - Problem when upscaling content. When the parallax between views is too great, eyes don't converge anymore and start to diverge meaning the objects are beyond innity. Cardboarding is a problem that usually appears when the content is downscaled to t a smaller display, whereas hyperstereoscopy is the exact opposite and is usually visible when content intended for a small display is upscaled to t a larger display. In cardboarding, when the content is downscaled the interocular distance is also downscaled by the same integer factor, however, since interocular distance doesn't scale linearly it means that the content will appear to have a skewed depth. Objects in the scene still have some depth but as the incorrect interocular distance is incorrect the objects look like cardboard cutouts, hence the term cardboarding. When content for a small display is upscaled to t a larger display the interocular distance is again changed by an integer factor. Since the interocular distance is increased it also means that the disparity range for the scene changes. This usually results in diverging eyes rather than converging, so the eyes will start pointing away from each other, whereas in the normal case the gaze from both eyes meets somewhere in front of the viewer. When the gaze from both eyes doesn't meet, it means from the viewers point of view that the objects are beyond innity. An illustration of this is: In the original scene for the small display the objects furthest away are 300 units away from the viewer which translates to a maximum parallax of 200px on the screen. The scene is then upscaled by a factor of two to t a larger display, so the parallax is also increased from 200px to 400px. If the maximum allowed parallax for the larger screen is, for example, 300px the scaled content exceeds the maximum parallax so the eyes diverge and the content appears beyond innity. Figure 4.1 illustrates this problem.

15 4. Screen size problem and adaptive parallax Fixing parallax in post-production There are various ways for adapting the created stereoscopic content for dierent display sizes and resolutions. One way to accomplish this task is to use dierent methods of adjusting the parameters articially in post-production. The main advantage of this approach is that it can be done with the original director or cinematographer of the content and so it can be ensured that the content looks as intended. Another advantage is that powerful computers and renderfarms can be used to utilize sophisticated signal processing algorithms and to re-render the created content. 4.3 Automatic disparity correction on an end user device End user devices can range from really powerful desktop computers, to TVs and mobile phones. This means there are hundreds of dierent screen size and resolution combinations, so hundreds of dierent versions of the same content need to be made to suit the end users devices. In order to make stereoscopic 3D a feasible option, some of this scaling and display adaptation needs to be performed not by the content creator but by the end user device. Lang et al. researched this issue in their paper titled Nonlinear Disparity Mapping for Stereoscopic 3D. In the paper, they introduced a lightweight method for correcting disparity ranges, that can be implemented on devices that don't have massive amounts of processing power. The method presented in the paper is based on simple image warping rather than complex camera parameter adjustments or stereo regeneration techniques. The low computational complexity of this method makes it possible to run this processing on-the-y when the video is played on the device [8].

16 12 5. EXPERIMENTS To illustrate the eects of varying camera parameters, stereoscopic 3D material was rendered for the experiments. This material was composed of various images and videos rendered from dierent scenes of the open source movie Big Buck Bunny. Scenes from Big Buck Bunny movie provided an ideal base for the test renderings because all the original material and an entire studio backup, including project les, can be freely downloaded from the project website org/. The original version of the movie is rendered entirely in standard 2D which meant that for the purpose of the stereoscopic tests, the scenes needed to be rerendered into various stereoscopic 3D formats. 5.1 Tools Matlab R2007b was used for two main tasks; to create images to nd the comfortable disparity ranges for the screens and to accomplish the row interleaving needed by the displays. Stereoscopic Viewer was used to display videos and images on the displays. Blender was used to render scenes from Big Buck Bunny movie. It was run on Ubuntu Linux platform. Blender Stereoscopic Rendering plugin v was used to transform the Big Buck Bunny movie scenes' original camera into two new cameras, left and right. These were then used for the left and right views for stereoscopic viewing [9]. For the experiments, three dierent display devices were used, Vuon 46" 3D capable LCD-TV, Sharp 15" Laptop with Autostereoscopic Display and Acer 15.6" Laptop with 3D capability. 5.2 Experiments The rst thing that was done before any of the material was rendered was to establish a baseline for disparity ranges. In order to nd disparity ranges a script was written in Matlab that generated a series of images of a white cube on a black background. Each consecutive image added 1 pixel to the oset of the cubes which meant a total native pixel parallax change of 2 pixels. The oset ranges were from 0 pixels to 200 pixels for both the positive and negative parallax. Due to the sharp edges of the cube and the big contrast change from 100% black to white, meant when these

17 5. Experiments 13 Display Resolution(r x x r y ) NPP(px) Theoretical NPP (px) Vuon 46" 3D TV 1920x1080 ±50 ±120 Sharp Laptop 15" 1024x768 ±15 ±215 Acer Laptop 15.6" 1920x1080 ±20 ±356 Table 5.1: This table contains measured and theoretical Native Pixel Parallax (NPP) values for each display that was used in the experiments parallax values were used in the actual test renderings, the rendered scenes were always within the comfort zone for stereoscopic viewing. The baseline values for each display were found by circulating images until an image was found that showed either signicant crosstalk between views or the stereoscopic eect was lost for some other reason. The limiting factor for parallax for all the screens was always the crosstalk between views. Table 5.1 contains the measured values for each display. The next step in the process was to verify the disparity ranges and scene parameters using equation (5.1): NP P = IOD s cos(arctan( ry r x )) r x (5.1) This equation describes in pixels the distance between the eyes when mapped on a specic screen. Parameters in the equation are human interocular distance IOD in centimeters, the display diagonal size s in centimeters, r x and r y correspond to the horizontal and vertical resolution of the screen respectively. The equation gives the display's native pixel parallax. The NPP thus forms the upper boundary that must not be overstepped [10]. Two scenes were selected for the test renderings. The dierent properties of each scene made them good test scenes. Scene 1 - Rabbit had multiple overlapping and occluding objects and a continuous movement from the far parallax plane of the scene towards camera all the way to the near parallax plane of the scene. Scene 2 - River was more static in terms of movement and had only a few occluding objects but the main reasons this scene was chosen were the ne details of the grass and the lighting and shadows of the scene, particularly from the grass. These scenes were then converted to stereoscopic 3D using the Blender Stereoscopic rendering plug-in developed by Sebastian Schneider [9]. This plug-in converts a single camera in the scene into a stereoscopic camera rig, preserving the original camera parameters such as the depth of eld. This camera rig is illustrated in Figure A.1 in Appendix A. The plug-in makes it possible to place near and far planes into the scene. After the planes are set at the correct distances, the plug-in then calculates the parallaxes for both the near and far plane. The calculated parallaxes

18 5. Experiments 14 Display Scene IOD (BU) NP FP Vuon 46" 3D TV Scene 1 - Rabbit Vuon 46" 3D TV Scene 2 - River Sharp Laptop 15" Scene 1 - Rabbit Sharp Laptop 15" Scene 2 - River Acer Laptop 15.6" Scene 1 - Rabbit Acer Laptop 15.6" Scene 2 - River Table 5.2: This table describes Interocular distance in Blender Units, Near- and far parallaxes for each scene can then be compared against the NPP of each display to verify that the parallaxes are correct. The resulting stereoscopic camera rig parameters for the test scenes are illustrated in Table 5.2. For the actual experiments, all the material was optimized for Vuon 46" 3D TV and then viewed with the other displays to see how the resolution and screen size would aect the perceived depth. Renderings were done using NPP values obtained in the screen tests. The limiting factor for all of the scenes were the near objects (objects in front of the zero parallax plane) which meant that the maximum parallax obtained by objects behind zero parallax plane was considerably less than the maximum allowed NPP, generally about 60% of the maximum. All the resulting scenes from the test renderings provided an optimal baseline because of the natural and pleasant depth eect. After the scenes for the Vuon display were rendered, the Blender stereoscopic rendering plug-in was used to calculate the near and far parallaxes for the other two displays to see how they corresponded to the ranges obtained in the screen tests. These values can be found in Table 5.2. The values calculated for the other displays illustrated that near parallaxes are around two times bigger than was found to be optimal in the screen tests. Because the far parallax in the Vuon optimized scene is considerably less than is allowed, far parallaxes for the other displays are just within ranges for every other scene except for Scene 1 Rabbit when using Acer Laptop. Since the parallaxes are not within the allowed range, the content will appear to be skewed along the Z-axis and will only appear to have correct depth on the display for which it was originally intended. If interocular distance is halved for both scenes it brings both near and far ranges within allowed ranges for other displays but means a much shallower depth eect for the Vuon display since the allowed interocular distance is twice as much. This clearly illustrates the problems that arise from the use of various screen sizes and resolutions when displaying stereoscopic content.

19 15 6. CONCLUSIONS When generating content for dierent displays, it is important to take into consideration the properties of the intended display device. If the parameters are not scaled and tted to the particular display, it results in an unnatural and disrupted depth eect. Results from the experiments done for this paper conrm this. In order to make stereoscopic 3D a viable video format for the future regardless of the end-user device, these problems need to be addressed, for example, by using the image warping techniques discussed in chapter 3.

20 16 REFERENCES [1] Burke, P. Calculating stereo pairs [WWW]. [referred ]. Accessible from: stereographics/stereorender/. [2] IJsselsteijn, W.A., de Ridder, H., Vliegen, J. Subjective evaluation of stereoscopic images: Eect of camera parameters and display duration. IEEE Transactions on circuits and systems for video technology 10(2000)2, pp [3] RealD Inc. RealD Cinema system technical specications [WWW]. [referred ]. Accessible from: [4] MasterImage LLC MasterImage 3D Cinema system product brief leaet. [5] Dolby Laboratories Inc. Dolby 3D Digital Cinema technical specications [WWW]. [referred ]. Accessible from: professional/technology/cinema/dolby-3ddigital.html. [6] Jorke, H., Fritz, M Intec - A new stereoscopic visualisation tool by wavelength multiplex imaging. Ulm, Germany. 7 p. [7] Halle, M. Autostereoscopic displays and computer graphics. Computer Graphics, ACM SIGGRAPH 31(1997)2, pp e [8] Lang, M., Hornung, A., Wang, O., Poulakos, S., Smolic, A., Gross, M Nonlinear Disparity Mapping for Stereoscopic 3D. ACM Trans. Graph. 29, 4, Article 75 (July 2010), 10 p. [9] Schneider, S. Stereoscopic rendering in Blender[WWW]. [referred ]. Accessible from: [10] Ide, K., Sikora, T., 2010 Adaptive Parallax for 3D Television. 3DTV- Conference: The True Vision - Capture, Transmission and Display of 3D Video (3DTV-CON), 4 p.

21 17 A. APPENDIX Figure A.1: Blender camera setup and all the adjusted parameters

22 A. Appendix 18 Figure A.2: Test Scene 1 - Rabbit Figure A.3: Test Scene 2 - River