[vtk-developers] parallel camera: how to get image to fill viewport?

[Steve M. Robbins]

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