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  #1  
Old 10-22-2007, 07:01 PM
ajmurray ajmurray is offline
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Join Date: Aug 2007
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Stereo eye separation

Hello all,

Over the last few weeks I've set up Vizard in a number of stereo configurations, and I've recently noticed that the further away an object is, the larger the eye separation, and closer objects have a smaller eye separation. Shouldn't it be the other way around? With objects in the distance becoming more 2D as they go away? The Vizard stereo still looks fine, but other stereo applications seem to do it the other way. What am I missing here??

-ajm
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  #2  
Old 10-23-2007, 10:10 AM
farshizzo farshizzo is offline
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This is expected behavior. The further an object is from the user, the greater the distance between the projected image of each eye on the display surface. This is only normal for desktop stereo viewing (i.e. anaglyphic, shutter glasses, etc.). When using an HMD be sure to specify the viz.HMD flag with viz.go(), this will cause Vizard to use symmetric view frustums which will have an opposite effect on the object separation.
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  #3  
Old 10-24-2007, 12:15 AM
ajmurray ajmurray is offline
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The problem is that even though the offset produces a stereo image, the image goes back into the screen instead of coming out of the screen.

Currently objects remain behind the screen, with the closest objects being at screen depth. The case should be that the objects jump out of the screen, and the furthest objects should appear at screen depth.

Is there a way to switch this offset?

I tried using viz.go(viz.FULLSCREEN | viz.HMD | viz.STEREO) and it simply produced two identical view frustums.
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  #4  
Old 10-24-2007, 09:03 AM
farshizzo farshizzo is offline
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The default screen distance of Vizard is 1 meter. This means all objects less than 1 meter from the viewpoint will pop out of the screen. If you want objects further away from the screen to pop out then you need to use the fusionDistance command. The fusion distance will control the distance at which objects will appear to be on the screen. The default behavior of the fusion distance is to use the same value as the screen distance.

For example, the following script will create a line of balls going away from the viewpoint. Pressing a key 1-8 will set the fusion distance at the specified ball, so all balls before it should appear to pop out of the screen.
Code:
import viz
viz.go(viz.ANAGLYPHIC|viz.FULLSCREEN)

for x in range(8):
	viz.add('ball.wrl',pos=(0,1,3+x))
	vizact.onkeydown(str(x+1),viz.MainWindow.fusionDistance,3+x)
	
viz.add('tut_ground.wrl')
As I mentioned in my previous post, using the viz.HMD flag will create symmetric frustums and is only intended to be used with HMDs.
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  #5  
Old 10-24-2007, 10:56 AM
tobin tobin is offline
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Join Date: Feb 2003
Posts: 251
For a full discussion of stereoscopic rendering and HMD versus external displays, you may want to read the chapter on this topic. Below is a link to the online version or you can find it in your installed help:

http://www.worldviz.com/vizhelp/VizH..._rendering.htm
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