Mahdi Amiri. May Sharif University of Technology

Transcription

1 Course Presentation Multimedia Systems 3D Technologies Mahdi Amiri May 2014 Sharif University of Technology

2 Binocular Vision (Two Eyes) Advantages A spare eye in case one is damaged. A wider field of view (FOV). Maximum horizontal FOV of humans: ~200º (with two eyes) One binocular FOV (seen by both eyes): ~120º Two uniocular FOV (seen by only one eye): ~40º Binocular summation: The ability to detect faint objects is enhanced (neural summation). Perception of depth. Page 1

3 Depth Perception Cyclopean Image Cyclopean image is a single mental image of a scene created by the brain by combining two images received from the two eyes. The mythical Cyclops with a single eye Page 2

4 Depth Perception Cues (Cont.) Accommodation of the eyeball (eyeball focus) Focus by changing the curvature of the lens. Interposition Occlusion of one object by another Occlusion Page 3

5 Depth Perception Cues (Cont.) Linear perspective (convergence of parallel edges) Parallel lines such as railway lines converge with increasing distance. Page 4

6 Depth Perception Cues (Cont.) Familiar size and Relative size subtended visual angle of an object of known size A retinal image of a small car is also interpreted as a distant car. Page 5

7 Depth Perception Aerial Perspective Cues (Cont.) Vertical position (objects higher in the scene generally tend to be perceived as further away) Haze, desaturation, and a shift to bluishness Hight Shift to bluishness Haze Page 6

8 Depth Perception Light and Shade Cues (Cont.) Shadow Page 7

9 Depth Perception Cues (Cont.) Change in size of textured pattern detail. Page 8

10 Depth Perception Motion parallax Cues (Cont.) When an observer moves, the apparent relative motion of several stationary objects against a background gives hints about their relative distance. This effect can be seen clearly when driving in a car. Nearby things pass quickly, while far off objects appear stationary. Page 9

11 Depth Perception We see a single, Cyclopean, image from the two eyes' images. Cues: Stereopsis A person s eye are about 65mm apart from each other. The two eyes converge on the object of attention. The cube is shifted to the right in left eye's image. The cube is shifted to the left in the right eye's image. The brain gives each point in the Cyclopean image a depth value, represented here by a grayscale depth map. Page 10

12 Depth Perception Cues, Summary Monocular Cues (involve those cues that exist for a single eye) Accommodation of the eyeball Interposition (Occlusion) Linear perspective Familiar size and Relative size Aerial Perspective Light and Shade Change in size of textured pattern Monocular Movement Parallax Binocular Cues (Cues that involve both eyes) Stereopsis Page 11

13 3D Technologies Stereoscopic Types of 3D Displays Provides a different image to the viewer's left and right eyes (generally user has to use special spectacles). Autostereoscopic Uses optical components in the display, rather than worn by the user, to enable each eye to see a different image. Computer-Generated Holography (CGH) Create a light field identical to that which would emanate from the original scene. Volumetric displays Display points of light within a volume. Such displays use voxels instead of pixels. Page 12

14 Stereoscopy Definition Presenting two offset images separately to the left and right eye of the viewer. Three strategies: Have the viewer wear eyeglasses to combine separate images from two offset sources. Have the viewer wear eyeglasses to filter offset images from a single source separated to each eye. Have the light source split the images directionally into the viewer's eyes (no glasses required, Autostereoscopy). Page 13

15 Charles Wheatstone Stereoscopy Stereoscope Two Offset Sources A stereoscope is composed of two pictures mounted next to each other, and a set of lenses to view the pictures through. Each picture is taken from a slightly different viewpoint that corresponds closely to the spacing of the eyes. The left picture represents what the left eye would see, and likewise for the right picture. When observing the pictures through a special viewer, the pair of two-dimensional pictures merge together into a single three-dimensional photograph. First invented by Sir Charles Wheatstone in Page 14

16 Stereoscopy Viewers Two Offset Sources Conway Stereo Viewer Head-Mounted Display (HMD) An HMD with a separate video source displayed in front of each eye to achieve a stereoscopic effect. Page s-30s Stereo Viewer

17 Stereoscopy Autostereogram Filtering Single Source Anaglyph image Polarization of light Linearly polarized Circularly polarized Anaglyph (3D photograph) of a column head in Persepolis, Iran. A linear polarizer converts an unpolarized beam into one with a single linear polarization. The vertical components of all waves are transmitted, while the horizontal components are absorbed and reflected. Page 16

18 Autostereogram Stereogram 3D craze of the 90 s Page 17

19 Autostereogram Decoupling focus from convergence tricks the brain into seeing 3D images in a 2D autostereogram. Page 18

20 Autostereogram Stereogram 3D craze of the 90 s Multimedia Page 19 Systems, Spring 2011, Multimedia Mahdi Systems, Amiri, 3D Mahdi Technologies Amiri, 3D Technologies

21 Autostereogram Stereogram 3D craze of the 90 s Page 20

22 Autostereogram Viewing Instructions Magic Eye images may be easier to see if viewed on paper rather than a computer screen. If possible, print this image and follow the instructions below. (You don't need to print in color.) The hidden image Hold the center of the printed image right up to your nose. It should be blurry. Focus as though you are looking through the image into the distance. Very slowly move the image away from your face until the two squares above the image turn into three squares. If you see four squares, move the image farther away from your face until you see three squares. If you see one or two squares, start over! When you clearly see three squares, hold the page still, and the hidden image will magically appear. Once you perceive the hidden image and depth, you can look around the entire 3D image. The longer you look, the clearer the illusion becomes. The farther away you hold the page, the deeper it becomes. Good Luck! Page 21

23 Autostereogram Random Dot Autostereogram The hidden image Page 22

24 Autostereogram Random Dot Autostereogram Page 23

25 Dr. Bela Julesz Autostereogram Stereogram Random dot stereogram was invented by Dr. Bela Julesz in Fig. 1. By using uniform, randomly distributed dots, Dr. Julesz eliminated the depth cues that are inherent in recognizable images. Fig. 2. Within the rectangle select a group of dots that make Fig. 4. When the two up a small shape (here a circle). rectangles (Fig. 1 and Fig. 3) are viewed together as a Fig. 3. Create a new rectangle stereo pair, the image of the identical to the original rectangle, circle appears to float above except that the dots within the small the background. shape have been shifted to the left. Page 24

26 Christopher Tyler Autostereogram Birth of Autostereogram In 1979, Christopher Tyler, a student of Dr. Julesz, assisted by computer programmer Maureen Clarke, discovered that the offset scheme could be applied to a single image. The hidden image Page 25

27 Anaglyph Image Concept Red-blue glasses Page 26 Red-cyan glasses cyan = green + blue The anaglyph method produces two slightly offset images, each individually tinted in either red or cyan. The red-cyan glasses then filter the light appropriately, meaning individual eyes only see the image meant for them. The brain then merges the two slightly different images to produce the 3D effect. This is the main process currently being used on 3D Blu-Ray releases and on TV broadcasts.

28 Anaglyph Image How to create Concept Page 27

29 Anaglyph Image 3D Box Example Page 28

30 Anaglyph Image Computer Process Page 29

31 3D Technologies To be continued That s not all. Page 30

32 Polarization of Light Concept Linear Polarized 3D Glasses The polarised method is one which is becomming the method of choice when displaying 3D images. Two images are projected at right angles to each other which are then filtered by the polarising glasses, again meaning each individual eye only sees the image intended for it, much in the same was as the anaglyph method. Page 31

33 Polarization of Light Linear Eyeglass contain a pair of orthogonal polarizing filters Low-cost eyeglasses If viewers tilt their heads Corrupts Circular The most widely used technology for watching 3-D films in theatres Right-handed/Clockwise handed/clockwise circularly polarized light displayed with and without the use of components. This would be considered Left-handed/Counter-Clockwise Clockwise circularly polarized if defined from the point of view of the source. The Common Types of Polarizers Page 32

34 Polarization of Light Circular Polarization RealD glasses A Left-handed/counter-clockwise clockwise circularly polarized wave as defined from the point of view of the source. A right-handed/clockwise handed/clockwise circularly polarized wave as defined from the point of view of the source. Page 33

35 3D Technologies Concept Autostereoscopic Comparison of parallax-barrier and lenticular autostereoscopic displays. Note: The figure is not to scale. Example of parallax barrier. Each eye sees different pixels of the image. Page 34

36 3D Technologies Example devices Autostereoscopic The Nintendo 3DS uses parallax barrier autostereoscopy to display a 3D image. Page 35

37 3D Technologies Holography Invented in 1947 by Dennis Gabor. Holography is a technique that allows the light scattered from an object to be recorded and later reconstructed so that when an imaging system (a camera or an eye) is placed in the reconstructed beam, an image of the object will be seen even when the object is no longer present. Dennis Gabor, Page 36

38 Holography Concept Holographic recording process Holographic reconstruction process Page 37

39 Holography ABC ABC Workspace Holographic recording process Page 38

40 Holography ABC Interference Interference Page 39

41 Holography Diffraction Diffraction example Diffraction Page 40

42 Volumetric Display Voxels (3D Pixels) A series of voxels in a stack with a single voxel highlighted. Page 41

43 Volumetric Display Voxels (Different resolution) Different resolutions Filled with Color Page 42

44 Volumetric Display Voxels (Different edges) Page 43

45 Volumetric Display Different Materials on accordant positions of the car Voxels (Different materials) Page 44

46 3D Technologies A pair of CrystalEyes shutter glasses Pros Liquid Crystal (LC) Shutter Glasses Mostly eliminate "ghosting" which is a problem with other 3D display technologies such as RealD 3D Unlike red/cyan color filter 3D glasses, LC shutter glasses are color neutral enabling 3D viewing in the full color spectrum. Cons Flicker can be noticeable except at very high refresh rates, as each eye is effectively receiving only half of the monitor's actual refresh rate. LC shutter glasses are shutting out light half of the time... darker picture perceived by the viewer. Expensive glasses (Over $100) Shutter glasses are also matched to the TV so it may not be possible to use your shutter glasses with a different brand 3DTV. Page 45

47 3D Technologies Ghosting ABC Page 46

48 Multimedia Systems 3D Technologies Thank You FIND OUT MORE AT Page 47