3D Stereo Setup (Polarized Glasses)

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3D Stereo Setup (Polarized Glasses)

Postby Jan Huewel » Wed Dec 16, 2009 9:51 pm

Pandoras Box Media Servers allow to setup 3D realtime setups easliy.

The following technique will describe how to setup a 3D scene where 2D or 3D Layers can be moved in front or back of a stereo Projection Screen.

Before explaining the setup with the Pandoras Box Userinterface a few prerequisites are need to be in place.

A gray or silver screen that is suited for polarized projection. Plain white high gain screen material does not work as they diffuse the light projection too much so that a so called ghosting effect destroyes the illusion of seeing in 3D.

A silver screen refelects the polarized light much more precisely so that each eye gets to see only its dedicated content.

In order to separate the left from the right eye, two projectors with a polarized filter are needed for this setup.

Image

The example shown above shows the use of linear polarized filter setup.

It is important to make sure that the filters are oriented in such a way that the projected image of each projector can be seen only with one eye. Linear polarized filters have to be offest by 90° to each other.

Image

Please note some projectors offer built in polarized filters such as the ones from http://www.projectiondesign.com for example. If your projector does not support this kind of filter you can still use a glass or plastic filter in front of any lens.

Setting up the Pandoras Box Media Server for stereo 3D output:
First of all you need to make sure that both output are setup to projected as accurate as possible on top of each other.

The best quality results are archieved by placing the projectors as close as possible and to avoid to use any Keystone correction at all.

If there is no other way to setup the projectors the result of video and images will still look very good with keystonecorrection in place only the image borders might show little aliasing effects due to the scaling of the output.

I recommend to turn any projectors built-in keystone correction off and to make use only of the lensshift if needed and setup the to outputs to match each other from pandoras box with either the cameras keystone parameters or with the PB Warper.

Once both projectors are setup and the two outputs of Pandoras Box are perfectly aliged to overlay each other all you need to do is to offset the cameras x axis position slights by around 5-10 units.

Image

In order to work with layers in the 3D space around the screen it is recommended to to stay within a reasonable region of depth as not all audience willa dopt well to very near projections. 3D layers that are positioned far back are not that critical.

A good start is to postion a 2D background layer in the back and scle it up to cover the entire screen area.

Another 3D layer can then be placed in the center of the projection and positioned and moved in all dimensions.

To keep the illusion intact I recommend to avoid letting any 3D layer that is in negative z space (in front of the screen) touch or cross the borders of the screen as this would reduce the 3D effect a lot.

A good best practice is to scale an object down the more you come "out of the screen" - negative z space.
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Jan Huewel
 
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