"Jim Holsenback" <jho### [at] hotmailcom> wrote:
> Hola,
>
> I'm working on an idea and I'm not getting the results I expected, so before
> I flog this any further, I thought I'd post and see if it's even possible.
> For those who don't know what a cross screen filter is ..... check out this
> Wikipedia entry:
> http://en.wikipedia.org/wiki/Filter_(photography)#Cross_screen
>
> So my question is is this even possible in POV? I've constructed my filter
> (I'm using the fine wire grating method) and it dosen't work as expected. I
> think I'm missing the "diffraction" element of my filter. Since this is a
> pretty sharp group I imagine someone might have a few pointers to get me
> going in the right direction .... or tell me that it can't be done.
>
> Cheers Jim

The easiest way to do this would be to look at your scene through a thin box
(like a glass lens) with an appropriate ior and a surface normal applied.
You may need to scale the bump size of the grating filter up and the
spacing down to suit your needs.  You will also need heavy AA to make it
look good.  But it should and does work, I have used similar in the past
for both reflective and refractive surfaces.

-tgq

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