Aha! A model for media that I can understand. I hadn't realised, and not yet
worked out, about the middle of the media being the only area sampled with
the defaults. That seems to fit with what I've seen. Many thanks. I won't
need to use the union - great tip though - as the shallow box meets my
needs. I was just very confused as to what was going on.

--
Tom Melly
tom### [at] tomandluforce9couk
http://www.tomandlu.force9.co.uk

Jerome <ber### [at] inamecom> wrote in message
news:38D0D4E6.F3426478@iname.com...

> With the deeper box, nearly all samples are taken in the
> middle of the box where all the light from the light_source
> has been absorbed while going in. In standard POV, samples
> are taken at random, so for some points you've got a fair
> chance of having a sample that's taken near enough the side
> to be lighted. In MegaPOV with method 2 or 3, the samples
> are regularly spaced and all are taken inside.
> If you push the samples count waaayyy up, you'll notice
> that the effect diminishes... Another solution is to add
> another box completely transparent, hollow, shadowless...
> just inside your container to make POV take samples near the
> sides:
>
> #declare BoxB = // completely black (with white spots in
> POV, pure black in MP)
> union { // <-----------Add this
> box
> {
>   <-10000, -10000, -10000>
>   < 10000,  0,  10000>
>   pigment{rgbf<1,1,1,1>}
>   hollow on
>   interior{media{Plain_White_Scattering_Media}}
> }
> box {  // <-----------Add the following lines
>   <-9999, -9999, -9999>, < 9999, -1, 9999>
>   pigment { rgbf 1 }
>   hollow
>   no_shadow
> }
>

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