Christopher James Huff wrote:
>In article <web.3fb29a7b2d6843d5d947fdc0[at]news.povray.org>,
> "Omega" <nomail[at]nomail> wrote:
>
>> I'd like to create a sinusoidal shadow on an object.
>>
>> Does anyone have an idea on how to do that?
>
>Put a sinusoidal object between it and the light?

Yeah.. couldn't figure out how.. ;)

>> Here what I've tried: I created several boxes objects between the source
>> light and the object to be shadowed. I then set the light to be a an
>> area_light type. But...it creates a triangular shadow (when doing a line
>> profile in X).
>
>I'm having trouble understanding what kind of shadow you are trying to
>achieve. You want something sinusoidal in intensity rather than shape?
>You use the term "Ronchi" several times...you're trying to simulate a
>Ronchi grating?

Yes, I want a sinusoidal signal in intensity.. actually simulating a
defocused Ronchi grating

>Try a plane with a partially transparent texture instead:
>plane {-z, 1900 hollow
>    texture {
>        pigment {gradient x scale Ronchi_Line_Width
>            sine_wave
>            color_map {[0 rgb 1] [1 rgbf 1]}
>        }
>    }
>}

Oh great, that's what I was looking for!

Nice, it seems to work the way I want.. but is there a way to get rid of the
discontinuity occuring at x=0? (the sine phase starts at phi=0 and
increments in both direction, thus creating positive values over an entire
period of the sine)

>> Something I would have liked to try, is defocusing the shadow produced by my
>> boxes objects using some kind of lens...but I don't know how to do that.
>
>Well, fuzzy shadows can be had with an area light, but you already know
>that...if you're looking for a true diffraction effect, POV is incapable
>of simulating it.

Okay.. no problem, the hollow plane will do the trick

Thanks again,
O.

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