WATS Presentation Multi-projector displays using commercial of the shelf (COTS) projectors Andrew Jamison CEO, Scalable Display Technologies

Example Case: 50 COTS HD projectors on a 40’ dome Message: “It’s all about the system solution”…

The system as a “pixel pipeline”  COTS “home cinema” projectors  Color correction/control  Light/black levels  Color depth (10 bit)  Geometry correction  Accuracy & warp location  A word on texture filtering Image Generator Warping Function ProjectorScreen

Color Correction/Control  Projector color calibration is a requirement  Projector must have Ethernet connection & knobs to turn  Serial connections work but require more parts in the system  Set projector in “cinema mode”  Two approaches to calibrate color  Shaders – send corrected pixels to the projector “input”  Correct the projectors “output” – modify settings of the projector “Input” only Correction Projector “output” Corrected Available dynamic range Three projector illustration

Color Calibration Trade-offs  Input side  Offers opportunity for localized correction of “hot spots” and other aberrations  Faster to calibrate  One weak lamp can drag down the performance of the entire array  “Lowest common denominator”  Output side  Maximizes dynamic range of array  More difficult to execute  Requires communication with each individual projector make and model  Takes longer to calibrate

“Output” approach considerations  There are two typical methods to control projectors remotely  “menu based” control  Mimic a remote control –Slow and subject to missed commands  “value based” control  Can receive specific values  Much faster and more accurate Ask your vendor to provide “value based” control

Light/black levels  First consider impact of screen shape/finish  Part 60 4.d – surface contrast ratio – 5:1  cross reflectance…1 lux of ambient light (i.e. a small candle), the max perceivable contrast ratio is 500:1. A dimly lighted room with 30 lux of lighting would squash the maximum perceivable contrast ratio to 50:1 –“Black Level” – no more than.015 candelas/square meter (cd/m²) in an unlit portion of a displayed scene as measured from the pilot eye-point.  Contrast ratio of projectors  Low contrast results in low resolution but high contrast does not necessarily mean high resolution  High CR is a good goal but be careful of marketing numbers…did it say ANSI?  Look for iris and iris controls  Brightness  4.e - Not less than six (6) foot-lamberts (20 cd/m2).

Black level challenge Area of maximum shared light Edge-blended “tiled” example High contrast ratio projectors are required for good blends Projector 1 Projector 3Projector 4 Projector 2 Shared pixels and elevated black here

Color depth 10 Bit color through the entire pipeline makes for brilliant displays

Geometry Calibration  Objective is to align the pixels and blend the edges  Manual calibration  Practical and cost-effective for some scenarios  Small arrays and flat screen  Advanced tools are available but challenges persist  Fully automatic calibration  Domes, cylinder and other complex geometries are very difficult to correct manually  Fast, reliable and flexible

Geometric Accuracy  4.c - System Geometry –  5° even angular spacing within ±1° as measured from either pilot eye point and within 1.5° for adjacent squares.  Uniformity of a grid as measured by theodolite  6.e - The visual system must be free from optical discontinuities and artifacts that create non-realistic cues.  Geometric mesh must be free of aberrations or discontinuities  Some manual approaches suffer from this…

Geometric warping location  Three places to execute geometric warping  Projector  External box  IG  External box and projector warping  “application independent”  Can be fully automatic  Possibility for good filtering  IG warping  “application dependent” – requires SDK integration  Truly zero latency since warp is within the 16ms render cycle – (typically.15ms)  Also consider aliasing artifacts

Texture Filtering Basics Better quality re-sampling = better quality images Nearest neighbor Polynomial interp.Linear interpolation

F Horizontal Field Of View ~ 143 degrees Comparable to 50mm lens (8,400 arc minutes) 4,200 unique pixels needed ~ 5,000 projected pixels Including overlap 1 arc minute =.3 milliradians Each pixel =.6milliradians A view on resolution 4.f – Not greater than two (2) arc minutes (per pixel). Sony – 4K pixels / 100°

 One radian is the angle subtended at the center of a circle by an arc that is equal in length to the radius of the circle.anglesubtendedcirclearcradius  1 radian = 57.3°

Graphic Cards Allow for Resolution Higher  Multi-GPU technology (Vista only)  nVidia's 'SLI'  ATI's 'Crossfire‘  Quad output cards  Pixel shader abilities

It’s a system  Points of failure are:  Cables  Connectors  Power supplies  Simulators/FTD are controlled environments  Know screens, IGs, projectors  These are repeatable environments

4 Projector Dome, 220 Degrees.

Thank you