week 7 summaries [Aurelien]
A Practical Multi-viewer Tabletop Autostereoscopic Display
Autostereoscopic displays give a perception of 3D without wearing glasses and allow to see different images when moving around them.
There is 3 types of autostereoscopic display : holographic, volumetric and parallax-based.
Parallax based display could be made with:
– a barrier with holes. When both eyes of the user look in the same split they see different pixels.
– a lenticular barrier made with cylindrical lenses which direct the light in a particular direction.
Both techniques are only horizontal.
Some displays use a 2D array of lenslets for providing different view in horizontal and vertical but with low resolution and their limited view angle make them unusable for tabletop utilization.
Another technique the random hole display does not handle dynamic view points, provides a not enough good rendering and generates interference.
The authors provide an enhanced random hole barrier to overcome these problems.
They use a LCD screen with high resolution and applied a thin polyester film on it, this design overcome the problem of internal reflection. The mask pattern is generated with the Poisson disk sampling algorithm and a high density of holes give better brightness.
The problem of conflicting pixel (pixel seen on different views) is solved with a multiple view blended algorithm which give an average color of the pixel depending on the different views. For taking in account this algorithm the authors developed an hardware-accelerated algorithm with a 4 passes rendering corresponding to each step for applying the mask and correct the view.
The tests provided prove the efficiency of this systems but the author will try to use brighter, higher density LCD to keep brightness and quality with a low density of points and by the way decrease the conflict rate.
Scape: Supporting stereoscopic collaboration in Augmented and projective environments
This paper deals with SCAPE, a tool to make peoples collaborate in different remotes area. Many application in this field are not providing good enough results. The Scape use a HMPD, the researches have proven this technology is lightweight, provides a large field of view, low distortion objects and correct occlusion. With retro-reflective surfaces and multiple head-tracked HMPD they can create an application with multi viewpoints.
The application consist of piece with cylindrical display where users wearing HMPDs can manipulate a 3D data set. Reflective surface induce a gradual drop in luminance in case of a convex shape, while a concave shape with round corner minimize the this drop, more over to avoid cross talk a 9 meter upper bound of walk through is needed.
An optical tracker or an Ascension FOB magnetic tracker detects the HMPDs position and orientation. The Fob track hand and widget and DataGlove allow to interact with virtual objects. A vision based object tracking track the object in the scene while a magnifier widget magnified them. The link between users is made through a client-server architecture where each user can hide is own widget from the others. The scene appears differently for each user.
The authors planned to add in the future new features to make the collaboration more intuitive
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