Graphics II “3D” Graphics Cameron Miller INFO410 & INFO350 S INFORMATION SCIENCE Visual Computing

INFO410 S D Graphics (Cameron Miller) SLIDE 2 INFORMATION SCIENCE Outline  Depth Perception  Stereoscopic Techniques  Display Technologies

Depth Perception

INFO410 S D Graphics (Cameron Miller) SLIDE 4 INFORMATION SCIENCE Depth: Visual Cues  Overlapping objects (Occlusion)  Vertical position  Haze, desaturation  Change in size of textured pattern detail

INFO410 S D Graphics (Cameron Miller) SLIDE 5 INFORMATION SCIENCE Depth: Visual Cues  Linear perspective Typically illustrated as convergence of parallel lines g

INFO410 S D Graphics (Cameron Miller) SLIDE 6 INFORMATION SCIENCE Depth: Visual Cues  Subtended Visual Angle More specifically V (in radians) = 2 arctan(S/2D) f

INFO410 S D Graphics (Cameron Miller) SLIDE 7 INFORMATION SCIENCE Depth: Visual Cues  Accommodation of the eye l Kinesthetic sensations to the brain from tightening lense astr.gsu.edu/hbase/geoopt/imggo/eyeacc.gif

INFO410 S D Graphics (Cameron Miller) SLIDE 8 INFORMATION SCIENCE Depth: Visual Cues  Motion parallax l Objects further away appearing to move slower than close objects

INFO410 S D Graphics (Cameron Miller) SLIDE 9 INFORMATION SCIENCE Depth: Visual Cues  Stereopsis (Binocular Disparity) g

Stereoscopy

INFO410 S D Graphics (Cameron Miller) SLIDE 11 INFORMATION SCIENCE Stereoscopy  Any technique which is capable of creating the illusion of a three dimensional image.  If two images have the same angle of difference (deviation) and each eye sees only the corresponding image, a spacial effect is created.

INFO410 S D Graphics (Cameron Miller) SLIDE 12 INFORMATION SCIENCE Stereoscopic Techniques: Anaglyph  Two differently colored images (one for each eye)  When viewed through glasses with corresponding color filters, a stereoscopic image can be seen g

INFO410 S D Graphics (Cameron Miller) SLIDE 13 INFORMATION SCIENCE Anaglyph Problems  Ghosting l Where a color channel that should be filtered by the glasses is only partially filtered  Retinal rivalry l Where one image is seen for a few moments, then the other, then the first… etc. caused by brightness differences of colored objects  Color reproduction l Poor production of red through the cyan/red filters.

INFO410 S D Graphics (Cameron Miller) SLIDE 14 INFORMATION SCIENCE Anaglyphs: RGB Image & B/W Depth Map  Take original image and depth map and create a second image by displacing each pixel of the original by: 30.0 * (I-127.5) /  Where I is the intensity (0-255) of the corresponding pixel on the depth map and 30 is a user definable coefficient

INFO410 S D Graphics (Cameron Miller) SLIDE 15 INFORMATION SCIENCE Anaglyphs: RGB Image & B/W Depth Map  Many different ways to filter. Most simply, for each pixel:  It is suggested that the retinal rivalry can be reduced by applying gamma correction to brighten up the final red channel

INFO410 S D Graphics (Cameron Miller) SLIDE 16 INFORMATION SCIENCE Polarised Glasses  Instead of filtering the colors, the light waves are polarised at (usually) 45 and 130 degrees.  Corresponding filters on viewer glasses allow for stereoscopy /Wire-grid-polarizer.svg/680px-Wire-grid-polarizer.svg.png

INFO410 S D Graphics (Cameron Miller) SLIDE 17 INFORMATION SCIENCE Shutter Glasses  Present the image for the left eye while blocking the right eye’s view, then repeat for right eye (>120hz)  Full color 3D!

Autostereoscopy

INFO410 S D Graphics (Cameron Miller) SLIDE 19 INFORMATION SCIENCE Autostereoscopic Displays  Stereoscopy without the need for glasses  Support for multiscopy (“real” 3D)  Available Technologies: Lenticular lens Parallax barrier l Volumetric display

INFO410 S D Graphics (Cameron Miller) SLIDE 20 INFORMATION SCIENCE Autostereoscopy: Lenticular Lense  Array of magnifying lenses  When viewed with stereopsis, different images are magnified ak0.pinimg.com/736x/ee/43/7a/ee437a75 526ed30919a70d61b4aebc85.jpg content/uploads/2013/11/plastic.jpg

INFO410 S D Graphics (Cameron Miller) SLIDE 21 INFORMATION SCIENCE Autostereoscopy: Parallax Barrier  Opaque barriers over portions of the image source to induce stereoscopy.  If fixed, relies on the viewer maintaining a constant position to work.  Pixel count for each eye is halved. forums.com/threads/stereos copic-parallax.4/ screen.svg/512px-Parallax_barrier_vs_lenticular_screen.svg.png

INFO410 S D Graphics (Cameron Miller) SLIDE 22 INFORMATION SCIENCE Autostereoscopy*: Volumetric Display  “A display to create 3D imagery via the emission, scattering, or relaying of illumination from well defined regions in 3D space.” (Minoli, 2010)  Two general types: Swept Volume Static Volume

INFO410 S D Graphics (Cameron Miller) SLIDE 23 INFORMATION SCIENCE Volumetric Displays: Swept Volume  Projection of slices of a 3D scene onto a moving (typically rotating) display surface  Reliant on human persistence of vision

INFO410 S D Graphics (Cameron Miller) SLIDE 24 INFORMATION SCIENCE Volumetric Displays: Static Volume  Create imagery without any macroscopic moving parts in the image volume  Voxel activation produces a 3D image in space  Typically, electron beams interact with a gas filled volume to create light.

INFO410 S D Graphics (Cameron Miller) SLIDE 25 INFORMATION SCIENCE Volumetric Displays: Problems  Bandwidth! ~135GB/s to display 1024*768*1024 at 60fps  Difficult to create light out of nothing (Free space displays)  Difficult to create viewer position dependent effects (occlusion, opacity)

INFO410 S D Graphics (Cameron Miller) SLIDE 26 INFORMATION SCIENCE Autostereoscopy: The future.  Holographic displays Displays that provide all four eye mechanisms  Integral imaging Technology that allows the capture and reproduction of light fields (3D photography)

Head Mounted Displays

INFO410 S D Graphics (Cameron Miller) SLIDE 28 INFORMATION SCIENCE Head Mounted Displays  Displays right in front of the eye (CRT, LCD, OLED etc)  Most display only an image on the screen (VR)  Two different methods for AR Video See Through l Optical See Through

INFO410 S D Graphics (Cameron Miller) SLIDE 29 INFORMATION SCIENCE Head Mounted Displays: VST  Real world is captured with cameras and then replayed through the display  Stereoscopy support.

INFO410 S D Graphics (Cameron Miller) SLIDE 30 INFORMATION SCIENCE Head Mounted Displays: OST  A device capable of reflecting projected images, as well as allowing the user to see through the image into the real world.  Two main families of underlying technologies: Varifocal Mirror l Waveguide edia/commons/a/a8/A_Google_Gl ass_wearer.jpg

INFO410 S D Graphics (Cameron Miller) SLIDE 31 INFORMATION SCIENCE OST: Varifocal Mirror  A flexible curved mirror whose focal length can be changed rapidly, and can be positioned so that it reflects the image of a display monitor to the viewer.  Drawback: near objects do not obscure far objects g

INFO410 S D Graphics (Cameron Miller) SLIDE 32 INFORMATION SCIENCE OST: Waveguides  A structure that stops the dissipation of waves into three dimensional space. (e.g fibre optic cable)  Many different types: Diffractive Holographic Polarised l And more.

Exam Questions

INFO410 S D Graphics (Cameron Miller) SLIDE 34 INFORMATION SCIENCE Potential Exam Questions  Anaglyph is a common stereoscopic technique. How does it work, and how are any limitations addressed by other (non auto) stereoscopic techniques?  Compare and contrast parallax barrier and leticular lense autostereoscopic technologies  In a situation where fully immersive virtual reality is required, which display technology(s) would best suit and why?

INFO410 S D Graphics (Cameron Miller) SLIDE 35 INFORMATION SCIENCE Bibliography Foley, J. (1995). Computer graphics: Principles and practice (2nd ed.). Reading, Mass.: Addison-Wesley Minoli, D. (2011). 3D television (3DTV) technology, systems, and deployment rolling out the infrastructure for next-generation entertainment. Boca Raton, FL: CRC Press Rolland, J., & Fuchs, H. (n.d.). Optical Versus Video See-Through Head-Mounted Displays in Medical Visualization. Presence: Teleoperators and Virtual Environments, Sanftmann, H., & Weiskopf, D. (2011). Anaglyph Stereo Without Ghosting. Computer Graphics Forum,