mtxcoll nous apporta ses lumieres en ce 2007/08/14 16:14:
> "Hildur K." <hil### [at] 3dcafemailevery1net> wrote:
>> "mtxcoll" <mtx### [at] gmailcom> wrote:
>>> Hi, I'm experimenting on POV-Ray trying to make a realistic Earth-like sky
>>> using scattering media and need help finding a place to start. I haven't
>>> found any good tutorials on how to accomplish this, and my own attempts
>>> always seem to make the atmosphere look too dark or too bright.
>>>
>> Have you looked into Rune´s Fast Sky?
>> might be helpful
>>
>> http://runevision.com/3d/povgoodies/
>>
>> Hildur
> 
> Thanks! This is pretty useful as a guide for how my atmosphere should look
> like.  I was still hoping to use just media to create a sky, though, just
> to see how it could be done. I've hit a major hiccup though: even though I
> can get a consistently blue sky using Rayleigh scattering, when I try
> combining it with Mie murky scattering the sun's glare is enormous and I
> don't know how to reduce it. If I reduce the amount of light or density of
> the atmosphere too much I end up with a black sky. Here's my scene file so
> far:
> 
>   camera {
>     location <-4, 0, 0>
>     look_at <0, 0, 0>
>     rotate y*0
>     }
> 
>   light_source {
>     <1000, 0, 0>
>     rgb 3
>     looks_like {
>       sphere {
>         <0,0,0>, 10
>         pigment { color White }
>         finish { ambient 1 }
>         }
>       }
>     parallel
>     point_at <0, 0, 0>
>     rotate z*14
>     }
> 
>   plane {
>     y, -1
>     pigment { color White }
>     }
> 
>   sphere {
>     <0,0,0>, 300
>     pigment { transmit 1 }
>     hollow
>     interior {
>       media { // Rayleigh scattering
>         scattering {4, <50,128,194>/255*0.5}
>         density { rgb 0.005 }
>         }
>       media { // Mie Murky scattering
>         scattering {3, 1e-9}
>         density {rgb 1e-9}
>         }
>       }
>     }
> 
> 
Try lowering only the second media's density.
Apply a density modifier like spherical. Scale the spherical pattern by less 
than 300, something around 180 to 260 could be an acceptable radius. Play around 
with color_maps and scaling to modulate it's density.
Try using 2 containers, one for the raleigh model scattering, a second, smaller 
one, for the mie murky model.
You can also experiment with mode 5 "Henyey-Greenstein" with an exentricity from 
0.75 to 0.97. Higher values make the scattering more directional, tightening the 
hallow effect around the "Sun".

-- 
Alain
-------------------------------------------------
You know you've been raytracing too long when you know the teapot bezier patches 
by heart.

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