I'm looking for a way to produce a sphere with deep cracks in it, like a broken
marble, or say a moon that got hit hard by something big...?

Any help would be appreciated.

A.D.B.

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You can do that with textures but I would recomend to model the whole thing and
then complete the job with a good texture. Try with Wings3D.

"Anthony D. Baye" <Sha### [at] spamnomorehotmailcom> wrote:
> I'm looking for a way to produce a sphere with deep cracks in it, like a broken
> marble, or say a moon that got hit hard by something big...?
>
> Any help would be appreciated.
>
> A.D.B.

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"kike" <dry### [at] hotmailcom> wrote:
> You can do that with textures but I would recomend to model the whole thing and
> then complete the job with a good texture. Try with Wings3D.
>
> "Anthony D. Baye" <Sha### [at] spamnomorehotmailcom> wrote:
> > I'm looking for a way to produce a sphere with deep cracks in it, like a broken
> > marble, or say a moon that got hit hard by something big...?
> >
> > Any help would be appreciated.
> >
> > A.D.B.

I'm not entirely certain I know what you mean by "Model the whole thing"... but
I don't have Wings3D, and I really don't use anything but POV.  I've tried
creating the object as an Isosurface with cracks made using a crackle pattern,
but the cracks propagate straight through along an axis, rather than down from
the surface.

I think that what I need is a high-definition height map, with the crack drawn
in.  Something that I can wrap around a sphere...

At least that way, I'll be able to handle impact craters at the same time.

A.D.B.

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> I'm not entirely certain I know what you mean by "Model the whole thing"

I mean to model/sculpt the cracked sphere

> I don't have Wings3D, and I really don't use anything but POV.

Wings3D is a free subdivision modeler very easy to use and tuned to export
models to povray as meshes.
http://www.wings3d.com/

> I've tried creating the object as an Isosurface with cracks made using a crackle
pattern,
> but the cracks propagate straight through along an axis, rather than down from
> the surface.

this way you can do exactly the object you want and then export it to Pov

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Anthony D. Baye wrote:

> I think that what I need is a high-definition height map, with the crack drawn
> in.  Something that I can wrap around a sphere...

you can also wrap a crackle pattern around a sphere
using a spherical warp {}. Then the corresponding pigment
function should be suitable for use in the iso_surface by
subtracting it from the base sphere.

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Christian Froeschlin <chr### [at] chrfrde> wrote:
> Anthony D. Baye wrote:
>
> > I think that what I need is a high-definition height map, with the crack drawn
> > in.  Something that I can wrap around a sphere...
>
> you can also wrap a crackle pattern around a sphere
> using a spherical warp {}. Then the corresponding pigment
> function should be suitable for use in the iso_surface by
> subtracting it from the base sphere.

That didn't really work too well, and I tried several variations...

I have to say, I'm rather unimpressed with Wings3d, the controls seem rather
cryptic.  I'm not a PoV purist, but I feel all thumbs with modelers...

The more I think about it, the more I feel a height map might be the way to go,
but I have no idea of how to create a height map suitable for a spherical
mapping.

Regards,

A.D.B.

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On 11/18/2010 04:43 AM, Anthony D. Baye wrote:
> The more I think about it, the more I feel a height map might be the way to go,
> but I have no idea of how to create a height map suitable for a spherical
> mapping.

http://wiki.povray.org/content/Documentation:Reference_Section_7.3#The_HF_Macros

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Anthony D. Baye wrote:

> That didn't really work too well, and I tried several variations...

That depends of course on what you want to achieve.

I just gave it a try and came up with the following image:

http://news.povray.org/povray.binaries.images/thread/%3C4ce58bc6%40news.povray.org%3E/

The isosurface definition is given by the code snippet below:


#declare P_WARPED_CRACKLE = pigment
{
   crackle turbulence 0.3 scale 0.04
   warp {spherical dist_exp 0}
   color_map
   {
     [0.00 color rgb 0.00]
     [0.06 color rgb 0.85]
     [0.30 color rgb 0.95]
   }
}

#declare f_warped_crackle = function
{
   pigment {P_WARPED_CRACKLE}
}

#declare f_valleys = function(x,y,z)
{
f_warped_crackle(x/(f_sphere(x,y,z,1)+1),y/(f_sphere(x,y,z,1)+1),z/(f_sphere(x,y,z,1)+1)).red
}

#declare f_implicit = function (x,y,z)
{
   f_sphere(x,y,z,1.8+0.2*f_valleys(x,y,z))
}

isosurface
{
   function { f_implicit(x,y,z) }
   contained_by { box { -2,2  } }
   accuracy 0.001
   max_gradient 10
}

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I forgot to mention the snippet uses f_sphere() so
it requires an #include "functions.inc"

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