Thanks Peter... I think I understad your explanation. I'll give it a go when I get
time, and
get back to you if I can't get it to work.

All the best,

Andy Cocker

BTW Your image is my current wallpaper also.


"Peter Popov" <pet### [at] vipbg> wrote in message
news:33fktu0i6o8l8mi8lj3ee8br9q3t2reeob@4ax.com...
> On Tue, 19 Nov 2002 12:27:13 -0000, "Andrew Cocker"
> <mai### [at] andrewcockercouk> wrote:
>
> >How did you implement the subsurface scattering?
>
> It's quite easy, actually.
>
> First of all, you obviously need, well, subsurface scattering :), or,
> in POV terms, scattering media filling a hollow object. Make it white,
> so that it scatters all light equally. Make it realistic, i.e.
> extinction 1
>
> Then you need to ensure that light actually penetrates the surface.
> Give all your colors a filter 1 (easy in my case, as these are all
> image maps). With enough scattering on the inside, the white light
> from inside filters through the colored surface and it looks like the
> object is opaque.
>
> As you might have seen in my original post, this approach causes some
> problems at shallow angles, as the media does not scatter enough light
> to extinguish all of it and the background can be seen through. To
> avoid it, add an opaque interior_texture. For most realism, make it
> the same as the external one, though you may wish to remove reflection
> from it as it will only contribute to the render times and not to the
> image.
>
> Last, you need to avoid self-shadowing as it really kills the effect.
> Simply putting no_shadow won't do it because then the object will not
> cast a shadow on anything, and we don't want that. Light groups may be
> an option, but it's easier to separate the surface from the interior.
> Simply make two copies of the object, one being the "shell" - with
> texture and interior texture, and the other being the "interior",
> slightly smaller, with a clear pigment and object scattering media.
> Give the "shell" no_shadow and you're in business.
>
> To push things really on the cool side, give the "shell" some ior.
> This bends the image inside so that you get a distorted terminator
> line characteristic of subsurface scattering (see some MAX/Brazil
> images implementing a s. sc. shader).
>
> That's it, quite simple, really, but the result is good.
>
> >How noticeable an effect is it giving to the scene?
>
> See for yourself. First attachment is without, second is with.
>
>
> Peter Popov ICQ : 15002700
> Personal e-mail : pet### [at] vipbg
> TAG      e-mail : pet### [at] tagpovrayorg
>

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