Hi Chris,

With your help, I obtained images that I am expecting.
Thanks a lot.

Regards,

Phu

"Chris B" <nom### [at] nomailcom> wrote:
> "vinhphunguyen" <nvi### [at] gmailcom> wrote in message
> news:web.4852425d5fabdd0ab979a58c0@news.povray.org...
> > I just found one case the code does not work well. Imagine that, taking
> > your
> > simplified example, there is another layered sphere behind this one along
> > z
> > axis (so that the plane z = 0 does not cut it) and shifted some units
> > along x
> > axis. In this case, the slice image should not contain the second sphere.
> >
> > ... snip ...
> > #declare grain1 = 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>}}
> >  }
> >  ... snip ...
> > #declare grain2 = union{
> >  difference {
> >    sphere{<2,0,1>, 0.3 pigment {color rgb <1,0,0>}}
> >    sphere{<2,0,1>, 0.2 pigment {color rgb <0,1,0>}}
> >  }
> >  ... snip ...
>
> This is because you didn't incorporate the cube you mentioned in your first
> posting, but you can do this as follows:
>
> #declare grains = union{
>   object{grain1}
>   object{grain2}
> }
>
> // Add a concrete block around the grains,
> // cutting holes where the grains occur.
> #declare concreteblock = union{
>   difference {
>     box {-2,2 pigment {rgb 1}}
>     object{grains}
>   }
>   object{grains}
> }
>
> // Then cut away to expose the inside of the block
> difference {
>   object {concreteblock}
>   plane {z,0}
>   cutaway_textures
> }
>
> >
> > I switched from difference operation to intersection, then the second
> > sphere
> > disappeared but the first sphere showed only the outermost layer.
> >
>
> That sounds about right. Using 'intersection' in place of difference will
> just give you the other half of whatever you do the difference/intersection
> with. With the camera where it is, this would have given you the outside of
> the first sphere and nothing of the second. With the changes above, an
> intersection will give you the outside of the white box, unless you move the
> camera to <0,0,3.5>, in which case you'll again see the cut surface, but
> this time from the opposite side (so the other way round).
>
> Another technique that may simplify this is to use an onion pattern with a
> colour map to define each grain rather than actual concentric spheres. This
> also enables you to do gradual colour transitions if you wish to.
>
> #declare grain1 = sphere{<0,0,0>, 0.3
>   pigment {onion
>     color_map {
>       [0.0  color <0,0,1>]
>       [0.1  color <0,0,1>]
>       [0.1  color <0,1,0>]
>       [0.2  color <0,1,0>]
>       [0.2  color <1,0,0>]
>       [1.0  color <1,0,0>]
>     }
>   }
> }
>
> If you ever want two grains with the same colour pattern you can scale and
> translate one you've already defined. For example:
>
> #declare grain3 = object {grain1 scale 0.6 translate x}
>
>
> Regards,
> Chris B.

Post a reply to this message