Warp wrote:

>   I made a minimal scene which reproduces the phenomenon.
> 
>   Comment out the box, and the caustic highlight appears. With the box there's
> no caustic. If the box has a transmit value smaller than 1, the caustic appears
> on the top surface of the box but doesn't go through.
> 
>   I'm not sure why this happens.

According to the documentation, pass_through does not have
an effect on photons which have already hit their target. You
probably need to specify "refraction on" to get it to work.

Apart from that, I don't think I would expect photons to affect
media if the container object is tagged with pass_through ;)

Post a reply to this message

Christian Froeschlin <chr### [at] chrfrde> wrote:
> According to the documentation, pass_through does not have
> an effect on photons which have already hit their target. You
> probably need to specify "refraction on" to get it to work.

  If you do that, the caustics change drastically. The box is not "invisible"
to the photons.

> Apart from that, I don't think I would expect photons to affect
> media if the container object is tagged with pass_through ;)

  You might not expect it, but that doesn't mean you are right.

http://wiki.povray.org/content/Documentation:Tutorial_Section_3.7#Media_and_photons

-- 
                                                          - Warp

Post a reply to this message

Christian Froeschlin <chr### [at] chrfrde> wrote:
> According to the documentation, pass_through does not have
> an effect on photons which have already hit their target.

Does that mean there is no way that media interact with photons that have
already passed through a lens or some other target?
Doesn't the documentation also say "photons interact fully with media
blablabla"?

Post a reply to this message

> Christian Froeschlin<chr### [at] chrfrde>  wrote:
>> According to the documentation, pass_through does not have
>> an effect on photons which have already hit their target.
>
> Does that mean there is no way that media interact with photons that have
> already passed through a lens or some other target?
> Doesn't the documentation also say "photons interact fully with media
> blablabla"?
>
>
>

You can.
Just add photons{pass_through} to your container.
The photons will ignore the container, but NOT the contained media.


Alain

Post a reply to this message

Alain <aze### [at] qwertyorg> wrote:

> > Christian Froeschlin<chr### [at] chrfrde>  wrote:
> >> According to the documentation, pass_through does not have
> >> an effect on photons which have already hit their target.
> >
> > Does that mean there is no way that media interact with photons that have
> > already passed through a lens or some other target?
> > Doesn't the documentation also say "photons interact fully with media
> > blablabla"?
> >
> >
> >
>
> You can.
> Just add photons{pass_through} to your container.
> The photons will ignore the container, but NOT the contained media.
>
>
> Alain

Nope. Take a look at Warp's example and mine above. Doesn't seem to work for
photons that already hit a target!
What I really want are caustics projected on some kind of media so to say.

Post a reply to this message

ghostch <nomail@nomail> wrote:
> Nope. Take a look at Warp's example and mine above. Doesn't seem to work for
> photons that already hit a target!
> What I really want are caustics projected on some kind of media so to say.

  Photons do interact with media inside an object which has a "pass_through"
setting. In this case the problem is not with media per se, but something
else entirely. The photons are not going through the object regardless of
the keyword (and thus do not affect the media inside it).

-- 
                                                          - Warp

Post a reply to this message

Warp wrote:

> If you do that, the caustics change drastically. The box is not "invisible"
> to the photons.

hmm ... indeed. You also need to specify "collect off". Then your
box with rgbt 1 and ior 1.0 does not seem to change the caustics,
although it likely causes more internal calculations due to the
invisible ray intersection points. The media also shows up:

--------------------------------------------------------------
global_settings { max_trace_level 10 photons { count 10000 media 100} }
camera { location <0, 1, -5> look_at -y*.5 }
light_source { y*10, 1 }
plane { y, -2 pigment { rgb 1 } }

sphere
{ 0, 1
   pigment { rgb <.9, 1, .9> filter 1 }
   finish { specular .5 roughness .01 reflection { .1, .3 } }
   interior { ior 1.5 }
   photons { target reflection on refraction on }
}

box
{ <-2, -1.9, -2>, <2, -1.5, 2> hollow
   interior
   {
     ior 1.0
     media {scattering {1, 0.5*<1,0,0>}}
   }
   pigment { rgbt 1 }
   photons { collect off refraction on}
}
--------------------------------------------------------------

Post a reply to this message

ghostch wrote:
> Christian Froeschlin <chr### [at] chrfrde> wrote:
>> According to the documentation, pass_through does not have
>> an effect on photons which have already hit their target.
> 
> Does that mean there is no way that media interact with photons that have
> already passed through a lens or some other target?

No, it just means you can't use pass_through. See my other reply
in this thread for a modified example with caustics and media.

The tutorial may be a bit misleading when it states that you
need to specify pass_through for the media photons to work. In
that example it is required because photons enter the media
container prior to hitting the target.

Post a reply to this message

Christian Froeschlin <chr### [at] chrfrde> wrote:
> box
> { <-2, -1.9, -2>, <2, -1.5, 2> hollow
>    interior
>    {
>      ior 1.0
>      media {scattering {1, 0.5*<1,0,0>}}
>    }
>    pigment { rgbt 1 }
>    photons { collect off refraction on}
> }

  That makes it work, indeed.

-- 
                                                          - Warp

Post a reply to this message

"Christian Froeschlin" <chr### [at] chrfrde> wrote in message 
news:4b69c62b$1@news.povray.org...
> The tutorial may be a bit misleading when it states that you

i would appreciate it if you folks would start getting this kind of stuff 
resolved over on the wiki. i'm making some progress with the php to produce 
the v3.7 online view ... all right you bunch of mugs ... hop to it! (cracks 
whip)

jim

Post a reply to this message