Hi,
I hope this question wasn't asked before, but I couldn't find it.
I want to make a ray light travelling through media visible. Until it hits
the first object no problem. But I can not make the reflected ray visible.
I remember that I read somewhere that this is not possible. Is that right?
If not, can somebody tell me how to do it?

Thanks
stelzenegger

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> I hope this question wasn't asked before, but I couldn't find it.
> I want to make a ray light travelling through media visible. Until it hits
> the first object no problem. But I can not make the reflected ray visible.
> I remember that I read somewhere that this is not possible. Is that right?
> If not, can somebody tell me how to do it?


Media photons. Check the documentation for details. Watch out: they're slow
and difficult to get right.

 - Slime
[ http://www.slimeland.com/ ]

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"stelzenegger" <ste### [at] gmxde> wrote in message
news:web.3e2ecd893b7128c32278e9910@news.povray.org...
> Hi,
> I hope this question wasn't asked before, but I couldn't find it.
> I want to make a ray light travelling through media visible. Until it hits
> the first object no problem. But I can not make the reflected ray visible.
> I remember that I read somewhere that this is not possible. Is that right?
> If not, can somebody tell me how to do it?
>

AFAIK there is no problem with reflected photons being visible in media - you
are using photons I assume? (i.e. you have a photon block in your
global_settings block).

Also, you must add a photon{target reflection on [refraction on]} block to any
object (such as your mirror) that you want to affect photons. (all objects show
photons, but only target objects influence photons).

Check section 6.10.2 of the docs (and 6.10 in general).

If you're not using photons, then, no, you will not be able to show the
reflected beam (since there isn't one).

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stelzenegger <ste### [at] gmxde> wrote:
> I remember that I read somewhere that this is not possible. Is that right?

  As others have commented, it's perfectly possible.
  Here is a test image I made once:

http://www.cs.tut.fi/~warp/images/photontest.jpg

-- 
#macro M(A,N,D,L)plane{-z,-9pigment{mandel L*9translate N color_map{[0rgb x]
[1rgb 9]}scale<D,D*3D>*1e3}rotate y*A*8}#end M(-3<1.206434.28623>70,7)M(
-1<.7438.1795>1,20)M(1<.77595.13699>30,20)M(3<.75923.07145>80,99)// - Warp -

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Yes I'm using photons and for the first part of the way everything seems
right. I also have included the "photon"-block in the object. Do I have to
take special care about the surface finish/pigment or whatever to get
enough reflected photons to make them visible or does this not matter?

Thanks again for all replies
stelzenegger

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stelzenegger <ste### [at] gmxde> wrote:
> Yes I'm using photons and for the first part of the way everything seems
> right. I also have included the "photon"-block in the object. Do I have to
> take special care about the surface finish/pigment or whatever to get
> enough reflected photons to make them visible or does this not matter?

  You have tell that photons should be taken into account in media (they
are not by default). IIRC this is done in the photons block inside
global_settings. See the documentation for details.

-- 
plane{-x+y,-1pigment{bozo color_map{[0rgb x][1rgb x+y]}turbulence 1}}
sphere{0,2pigment{rgbt 1}interior{media{emission 1density{spherical
density_map{[0rgb 0][.5rgb<1,.5>][1rgb 1]}turbulence.9}}}scale
<1,1,3>hollow}text{ttf"timrom""Warp".1,0translate<-1,-.1,2>}//  - Warp -

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>
>  You have tell that photons should be taken into account in media (they
>are not by default). IIRC this is done in the photons block inside
>global_settings. See the documentation for details.

Yes, I've don this. otherwise I couldn't see the first part of the ray. Only
after the ray hits the reflecting surface, I can't see it anymore.

stelzenegger

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Dang, I had to cancel that first reply  :-X

"stelzenegger" <ste### [at] gmxde> wrote in message
news:web.3e2fa78caa5a7cdc2278e9910@news.povray.org...
>
> after the ray hits the reflecting surface, I can't see it anymore.

What might be happening, if you have indeed set up everything else as
needed, is that the photon count or spacing is insufficient. Try raising the
count or decreasing the spacing in global_settings {photons {}}. For
example, spacing 0.02 or less is usually okay but you might need it to be
lower (also try higher if it works, speed issue). I don't use count much so
I'd be guessing that number. Only one of
those are needed.

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"stelzenegger" <ste### [at] gmxde> wrote in message
news:web.3e2fa78caa5a7cdc2278e9910@news.povray.org...
>
> >
> >  You have tell that photons should be taken into account in media (they
> >are not by default). IIRC this is done in the photons block inside
> >global_settings. See the documentation for details.
>
> Yes, I've don this. otherwise I couldn't see the first part of the ray. Only
> after the ray hits the reflecting surface, I can't see it anymore.
>
> stelzenegger


Can you post a *minimal* scene that demonstrates your problem? (you can either
include the scene code in a post, or, if attaching a scene, post to
binaries.scene-files)

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OK, here's the code

#include "colors.inc"
#include "metals.inc"

global_settings {
   assumed_gamma 1
   photons {
      //  spacing 0.02
      count 150000
      media 100, 2
      }
   }

media {
    scattering {1, color White extinction 0}
    method 3
    intervals 1 samples 4
    }

light_source {
   <22.36,25,10>
   color 2*Red
   spotlight
   radius 0.1
   falloff 1.5
   tightness 5
   point_at <38,7,10>
   photons {
     reflection on
     refraction off
     }
   }

camera {
   location <20,25,-10>
   look_at <45,0,15>
   }


plane { y,0
   pigment {color CornflowerBlue}
   photons {
     reflection off
     refraction off
     }
   }

#declare cantilever=
   box {
      <0,0.25,3>,
      <25,0.26,-3>
      texture { T_Gold_5E }
      photons{
         target
         reflection on
         refraction on
         //collect off
         }
      }


object {cantilever
   finish {reflection }
   rotate <0,0,-10>
   translate <22.36,7.759-0.5,10>
   }

box {
   <-0.5,-7.5,-7.5>
   <0.5,7.5,7.5>
   pigment {color Gray90}
   rotate <0,0,25>
   translate <58,15,10>
   photons{
      target
      reflection on
      refraction off
      collect on
      }
   }

I tried count up to 15M and spacing down to 0.0002 (wow that takes time)
with no effect.

stelzenegger

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