> Hi all,
> I'm a newbie.. I've two problems with this file:
> 1) there is no media scattering on the central beam (that collimated by the
> reflector) while there is scattering on the direct radiation. How to obtain
> light scattering from the central beam?
> 2) The central beam is not uniform, but it appears so: the spot is saturated.
> How to avoid this? How to have a more gradual representation of the
> illumination? (note: this happens always, also even when the media scattering is
> not present).
>
> Thanks anybody!
>
> /////////////////////////////
>
> global_settings
> { photons
>    { count 5000

That's a very small value. You should use AT LEAST 10 times that amount, 
more probably even something like 100 to 1000 times more.
I prefer to use spacing. Try replacing your count by spacing 0.3.

>     media 100   //  This parameter has no influence !?

It allow your media to receive photons. Without it, no photons effect 
will be visible in your media.

>    }
> }
>
> #if (1)
>          camera { location<-60,30,-150>  look_at<50,-20,0>  angle 60} // lateral
> prospective view
> #else
>          camera {orthographic location<5,0,0>  look_at<50,0,0>}   // frontal
> orthographic view
> #end
>
> // screen
> #declare xpos = 60;
> box {
>       <xpos, -60, -60>,<xpos+10, 60, 60>
>          pigment {rgb<1,1,1>}
>          finish {ambient 0.1 reflection 0 diffuse 1}
>          photons {target}
NOT needed. This object collect the protons, it never reflect nor 
refract them.
> }
>
> #declare lampandreflectorxpos = -20;
>
> // lamp
> light_source
> {<lampandreflectorxpos, 0, 0>,
>    color rgb<1, 1, 1>  * .1
>    //area_light z,y,4,4
This is a realy bad area_light array. You should reasonably don't go 
under 9,9 and use adaptive. circular orient is also very usefull.

>    photons { refraction off reflection on }
Not needed as it is, use photons{area_light} if you plan on using an 
area_light.

> }
>
> #if (0) // stop for the direct radiation, placed in front of the lamp
> cylinder
> {<lampandreflectorxpos+1,0,0>,<lampandreflectorxpos+1.5,0,0>,1.5}
> #end
>
> #if (1) // smoke block for scattering
> cylinder {<lampandreflectorxpos-3, 0, 0>,<xpos+1, 0, 0>, 60
>    pigment { rgbt 1 }
>    interior {media {scattering { 1, rgb .05 extinction 0}}}
>    hollow
Here, adding photons{passthrough} can prove usefull whenever the 
light_source is outside the container and your target is in or beyong it.
Not absolutely needed here as the light is inside the container. It's 
good idea to take the habit of adding that just in case.
> }
> #end
>



Alain

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