"houmr" <nomail@nomail> wrote in message 
news:web.4aeec54aeee70a117fab4e430@news.povray.org...
> Leroy Whetstone <lrw### [at] joplincom> wrote:
>
>> What are you trying to do with this? There maybe other things you could 
>> do
>> other than use 'matrix'. ...
>
> In fact the result of the transformation is kind of uneven shearing...
> I need to use this transformation to compensate a distortion involved by 
> an
> optical system while projecting the rendered images. Since the models are 
> of
> arbitrary and real sceneries, I doubt being able to convert it to 
> isosurfaces.
>

If it's to address real-world projection issues then it may be possible to 
do what you want in two passes:

Pass 1 - Render the scene as normal (or use a scanned photo).
Pass 2 - Apply the image to a surface within a scene that emulates the 
physical screen, projector and potentially any strange optics. The camera or 
cameras can be positioned where the projector would be in the equivalent 
real-world environment, using appropriate lens settings so that you get 
images that are appropriately distorted.

I recall that someone was using this sort of technique a few years back to 
adjust images projected from 4 projectors onto a cylindrical screen so that 
they could mesh the images together correctly into a full 360 degree image.

Regards,
Chris B.

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