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Old 01-19-2006, 04:38 AM
pkhoosh pkhoosh is offline
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Viewing Projection


I need to make sure that the object I have in my virtual world is perceptually plausible. For example, I need the size to be appropriate with the distance the object is from the camera.

Are there built in features from Vizard that allow this check?

Essentially, I need to know the distance the object is from the camera and the objects size. I can measure the physical projection on the screen to make check the ratio.

I have attached an image from Van Dam's lecture on Viewing.

Many thanks,

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File Type: jpg parallel_projection.jpg (40.8 KB, 839 views)
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Old 01-23-2006, 09:22 PM
tobin tobin is offline
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Join Date: Feb 2003
Posts: 251
The commands you'll need to use are:


Unless each is set correctly for your view location, the resulting imagery will not be projectively equivalent to a real object.

Also, if invoking fullscreen mode be sure to use the viz.FULLSCREEN flag rather than the viz.HMD flag as the former correctly calculates the slightly asymmetric view frustums appropriate for stereo viewing of a monitor (e.g., shutther glasses). viz.FULLSCREEN also assumes that you are centered about the screen's primary axis. If this is not the case (e.g., user if being head tracked and free to move head side to side) then you must manually calculate the correct view frustums for both the left and right eyes using the <window>.frustum command.
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Old 01-25-2006, 09:52 AM
pkhoosh pkhoosh is offline
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Thanks for the reply.

I was wondering if there is a command in Vizard that will give me the size of the virtual object. I realize that Vizard allows me to scale objects but I would like to know the original size. I figure I can get this from 3DSMAX, but I'm not exactly sure how to go about it in that tool.

Essentially, by getting the AB measure, with respect to the diagram in this post, I only have to adjust the parameters for the distance to the monitor (CD) and the distance the virtual object is from the camera (DB). The distance to the monitor, CD, is fixed since people can only be so far from the screen.

Many thanks,

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