Dear Chris,

Thank you very much for your help. It works well :-)

Best regards,

Vinh Phu

"Chris B" <nom### [at] nomailcom> wrote:
> "vinhphunguyen" <nvi### [at] gmailcom> wrote in message
> news:web.48513efe78241c82b979a58c0@news.povray.org...
> > Dear all,
> >
> > I would like to generate images like the ones in the right column at this
> > link
> > http://www.micthemodel.org/pages/examples.html (Sorry but I can not post
> > attachment).
> >
> > These images are in fact 2D slices of a 3D image that is a cube containing
> > a set
> > of layered spheres. A layered sphere is a set of concentric spheres of
> > different
> > colors. In my program (in fact, this is the visualisation of cement
> > hydration
> > simulation), I have the coordinate and radius of the spheres and the color
> > as
> > well.
> >
> > ...
> >
> > With this one, I did see the spheres but just one color CYAN.
> >
>
> I think you need to do a couple of things.
>
> Firstly, when you slice through, use the 'difference' CSG operation with the
> 'cutaway_textures' keyword, so that the slices through the objects retain
> their original textures.
>
> Secondly you need to difference the second largest sphere from the largest,
> the 3rd largest from the second largest etc. Otherwise, when you slice
> through the union of concentric spheres the section through the smaller
> spheres produce concurrent surfaces with the larger spheres and most of the
> surfaces won't display the colour you want. In fact you'll only get the
> colour you want displaying properly for the outermost object.
>
> Here's a simplified example:
>
> camera {location <0,0,-1> look_at 0}
> light_source {   <0,0 ,-100>, rgb 1}
>
> #declare MySpheres = union{
>   difference {
>     sphere{<0,0,0>, 0.3 pigment {color rgb <1,0,0>}}
>     sphere{<0,0,0>, 0.2 pigment {color rgb <0,1,0>}}
>   }
>   difference {
>     sphere{<0,0,0>, 0.2 pigment {color rgb <0,1,0>}}
>     sphere{<0,0,0>, 0.1 pigment {color rgb <0,0,1>}}
>   }
>   sphere{<0,0,0>, 0.1 pigment {color rgb <0,0,1>}}
> }
>
> difference {
>   object {MySpheres}
>   plane {z,0}
>   cutaway_textures
> }
>
> Regards,
> Chris B.

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