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List:       vtk-developers
Subject:    Re: [vtk-developers] parallel camera: how to get image to fill
From:       "Steve M. Robbins" <steven.robbins () videotron ! ca>
Date:       2005-11-18 3:48:42
Message-ID: 20051118034842.GD5067 () nyongwa ! montreal ! qc ! ca
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On Wed, Nov 16, 2005 at 10:27:07PM -0500, David Gobbi wrote:

> [...]  I have done a bit of experimenting, using both "height/2" and
> "(height-1)/2" as the parallel scale.
> 
> I can confirm that, empirically, "(height-1)/2" works better.  Surprisingly
> the only difference for me was that, with "height/2", the rightmost column
> of the image was chopped.  I would have expected the center row and
> center columnt to have been chopped... it must have something to do with
> the way rounding is done.  Apart from the rightmost column, both gave
> results identical to vtkImageMapper.  The vtkImageMapper uses
> glDrawPixels to exactly map each image pixel to a screen pixel, and
> can be considered ground truth.
> 
> Did you note any image differences when using height/2 instead of
> (height-1)/2, or just the difference in the coordinate mapping?

I was mainly guided by the coordinate mapping.  

We've put VTK into an existing imaging application and it's very
important that we understand the world->screen transform.  In
particular, we must be able to produce the same results as we
currently do.  That's why I'm a bit hung up on understanding
the transformation.

Regards,
-Steve


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