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I thought I'd take another shot at a decent sand texture; this is the
result of my first pass. It has all sorts of things wrong with it, but
it's not a bad start. :-) I'm not so much aiming for photorealistic sand
as I'm shooting for something that people instantly recognize as sand.

Whenever anyone posts sand images up, people complain about not seeing
sand grains, even if the sand in question is so far away that you
wouldn't be able to see the sand grains. The general solution to this
seems to be to have some sort of patterning going on at just about the
pixel level, where you can just see that there is something going on,
but you can't really see what.

The problem that I've had with this is that you have to tune your
patterning to the resolution you're rendering at. If you render at a
lower resolution, the patterning disappears; if you render at a higher
resolution, the larger-than-realistic "sand grains" become glaringly
obvious.

This also marks the first time I've tried to do subsurface scattering. I
didn't realize just how easy it is to set up, actually.

BTW, does anybody know if it's possible to make subsurface scattering
and normal perturbations play well together?

- --
William Tracy
afi### [at] gmailcom -- wtr### [at] calpolyedu

You know you've been raytracing too long when you stop using a
protractor to measure angles because you can do it just by looking.
    -- Taps a.k.a. Tapio Vocadlo
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I'm starting to come up with some stuff that I want to build sand
castles in. :-)

I'm starting to wonder if all my "details" are really helping or
hurting. Here's two renders, one with lots of yummy little patterns, and
one that's completely flat except for the subsurface scattering.

Speaking of subsurface scattering, just a little goes a long way. I
probably overdid the scattering media in these images, because
everything looks like its underwater. Which is still cool. ;-)

- --
William Tracy
afi### [at] gmailcom -- wtr### [at] calpolyedu

You know you've been raytracing too long when you thought the infamous
Book of Questions would have deeper stuff in it, like "If you could only
use one renderer, which would it be?', etc.
    -- Taps a.k.a. Tapio Vocadlo
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It's useless in animations, but have you tried the 'crand' option?

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Mark Birch wrote:
> It's useless in animations, but have you tried the 'crand' option?

It works better than I expected, actually.

(...and sorry for not remembering to convert those other pictures to jpg
before uploading them.)

- --
William Tracy
afi### [at] gmailcom -- wtr### [at] calpolyedu

You know you've been raytracing too long when you can remember back to a
time when you thought raytracing was a guy named Ray sitting at a desk
tracing.
    -- Ken Tyler
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"William Tracy" <wtr### [at] calpolyedu> schreef in bericht 
news:47461080@news.povray.org...
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>
> I'm starting to come up with some stuff that I want to build sand
> castles in. :-)
>
> I'm starting to wonder if all my "details" are really helping or
> hurting. Here's two renders, one with lots of yummy little patterns, and
> one that's completely flat except for the subsurface scattering.
>

Sand is - at the same time - easy and complicated to do. Imo, your renders 
look well. I suppose that the technique used depends on the type of scene 
one wants to build and the effect one wants to convey. This means that there 
is no definitive solution, or so I experienced myself. Using crand, like 
Mark says, can help, although I do not particularly like it. Perhaps using 
more contrast between the "grain" colors gives even better results. That, of 
course, depends on the type of sand one wants to render.

Thomas

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"Thomas de Groot" <t.d### [at] internlDOTnet> wrote:
> "William Tracy" <wtr### [at] calpolyedu> schreef in bericht
> news:47461080@news.povray.org...
> > -----BEGIN PGP SIGNED MESSAGE-----
> > Hash: SHA1
> >
> > I'm starting to come up with some stuff that I want to build sand
> > castles in. :-)
> >
> > I'm starting to wonder if all my "details" are really helping or
> > hurting. Here's two renders, one with lots of yummy little patterns, and
> > one that's completely flat except for the subsurface scattering.
> >
>
> Sand is - at the same time - easy and complicated to do. Imo, your renders
> look well. I suppose that the technique used depends on the type of scene
> one wants to build and the effect one wants to convey. This means that there
> is no definitive solution, or so I experienced myself. Using crand, like
> Mark says, can help, although I do not particularly like it. Perhaps using
> more contrast between the "grain" colors gives even better results. That, of
> course, depends on the type of sand one wants to render.
>
> Thomas

Hi

I was busy in RL those two last weeks and could not read much here. William,
your work seems very interesting. Would you mind, when achieved or partial,
sharing things so that I can integrate this nice stuff in TerraPOV?

    Regards

      Bruno

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William Tracy <wtr### [at] calpolyedu> wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>
> I'm starting to come up with some stuff that I want to build sand
> castles in. :-)
>
> I'm starting to wonder if all my "details" are really helping or
> hurting. Here's two renders, one with lots of yummy little patterns, and
> one that's completely flat except for the subsurface scattering.
>
> Speaking of subsurface scattering, just a little goes a long way. I
> probably overdid the scattering media in these images, because
> everything looks like its underwater. Which is still cool. ;-)
>
> - --
> William Tracy


I like these two images, individually. Is there a way that you could merge the
materials, with the grainy one in the foreground fading to the smooth one in the
midground?

Stephen

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"Stephen" <mcavoys_AT_aolDOT.com> wrote:
> William Tracy <wtr### [at] calpolyedu> wrote:
> > -----BEGIN PGP SIGNED MESSAGE-----
> > Hash: SHA1
> >
> > I'm starting to come up with some stuff that I want to build sand
> > castles in. :-)
> >
> > I'm starting to wonder if all my "details" are really helping or
> > hurting. Here's two renders, one with lots of yummy little patterns, and
> > one that's completely flat except for the subsurface scattering.
> >
> > Speaking of subsurface scattering, just a little goes a long way. I
> > probably overdid the scattering media in these images, because
> > everything looks like its underwater. Which is still cool. ;-)
> >
> > - --
> > William Tracy
>
>
> I like these two images, individually. Is there a way that you could merge the
> materials, with the grainy one in the foreground fading to the smooth one in the
> midground?
>
> Stephen

I used a kind of 'fadeaway' technique for my snow texture for TerraPOV, and I
posted recently and test render here. It is based on the distance wrt camera
(use of spherical pattern): when near it is one texture, when far it tends to
be a plain color (or whatever else). I intend to integrate fadeaway texturing
macros like this in TerraPOV, because terrain pigments become plain colors with
distance. Something like this can be applied to sand (same problem). It can also
be used for other purposes, of course.

Currently, it is coded as:
// --------------------------------------------------------------
// Parameters:
//    _color
//        Color of the snow. Can be C_SNOW_COLOR_BLUEISH.
//    _distance
//        Distance where the texture becomes a plain color
//    _scale
//        Scale for the near aspect of the texture
//
#macro TP_SnowFadeaway (_color, _distance, _scale)
    #local _t = texture
    {
        pigment_pattern {spherical scale _distance}
        texture_map
        {
            [0 TP_FarSnow(_color)]
            [.8 TP_SparkleSnow(_color, _scale)]
            [1 TP_SparkleSnow(_color, _scale/3)]
        }
    };
    _t
#end
// --------------------------------------------------------------

with TP_FarSnow() and TP_SparkleSnow() as other texture macros. This snow
texture is quite complex, but I think the result is OK.

I'll probablly define a general convenience macro with the following interface

#macro _tp_make_fadeway (_texture1, _texture2, _distance, _campos)
   // use of a more generic macro with thresholds and scales
#end

If this can help...


    Bruno

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Wow, this is nice!

Time ago I used this sand texture:

#declare t_sand=texture {
     pigment {
        granite
        color_map {
           [ 0.0     rgbft <0.670588, 0.505882, 0.321569, 0.0, 0.0> ]
           [ 1.0     rgbft <0.941176, 0.878431, 0.792157, 0.0, 0.0> ]
        }
        turbulence 0.75
        ramp_wave
        scale  0.01
     }
    //finish { crand 0.1 }
}

But the one you realized is more impressive.
;-)
Paolo

>"William Tracy" <wtr### [at] calpolyedu> ha scritto nel messaggio
news:47465d91$1@news.povray.org...
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>
> Mark Birch wrote:
> > It's useless in animations, but have you tried the 'crand' option?
>
> It works better than I expected, actually.
>
> (...and sorry for not remembering to convert those other pictures to jpg
> before uploading them.)
>
> - --
> William Tracy
> afi### [at] gmailcom -- wtr### [at] calpolyedu
>
> You know you've been raytracing too long when you can remember back to a
> time when you thought raytracing was a guy named Ray sitting at a desk
> tracing.
>     -- Ken Tyler
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----------------------------------------------------------------------------
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"Bruno Cabasson" <bru### [at] alcatelaleniaspacefr> schreef in bericht 
news:web.4746b46aee83a16ce8ba46670@news.povray.org...

> I used a kind of 'fadeaway' technique for my snow texture for TerraPOV, 
> and I
> posted recently and test render here. It is based on the distance wrt 
> camera
> (use of spherical pattern): when near it is one texture, when far it tends 
> to
> be a plain color (or whatever else). I intend to integrate fadeaway 
> texturing
> macros like this in TerraPOV, because terrain pigments become plain colors 
> with
> distance. Something like this can be applied to sand (same problem). It 
> can also
> be used for other purposes, of course.
>

Another possibility, I guess, would be to use the boxed or the cylindrical 
patterns. Maybe cylindrical would be better than spherical in a landscape? 
What do you think?

Thomas

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