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> Hello,
> I don't know why my reflector doesn't reflect photons. With scattering and an
> extinction value I should be able to see the area inside the cilindrical
> reflector slightly brighter than the area outside. Furthermore, the image is the
> same despite the value of "reflection" I use.
>
> Another question. Please, could someone explain me what the extinction value
> means?. Is it related to the Beer-lambert law, as I have read at the newsgroups
> or only a percentage of the scattered light?
>
> The code:
> #version 3.7;
>
> global_settings { ambient_light 0
> photons {spacing 0.1 max_trace_level 5 media 100,1 radius 0.5 autostop 0}
> assumed_gamma 1.0
> }
This looks OK
I'd remove radius 0.5. In my experience, it tend to cause some problems
if not set exactly right.
You don't need max_trace_level 5: It's the default value.
>
> //Container box
> box {<-11,-11,-31><11,11,31> hollow
> texture {pigment {color rgb 1}}
> interior { media { scattering {1, color rgb <0.5,0.5,0.5> extinction 0.1}
> method 3 intervals 1 samples 100 collect on} }
> photons {pass_through}
> }
You may want to make the box thinner, or reduce the density of your
media. If you get pure white with only the light, the reflected photons
can't show.
method 3 is the default and don't need to be specified.
With method 3, intervals default to 1 and must be left unchanged. Beter
to leave that one out.
>
> //camera
> camera {orthographic location <0,0,30.5> up <0,0,1> look_at <0,0,0> angle 50}
>
>
> //Source
> light_source { <0,0,0> rgb <1,1,1> fade_distance 1 fade_power 2
> photons{reflection on refraction on}
> }
This photons block is useless. By default, all light_source, except
shadowless, DO emit photons.
You need the photons block to turn on the area_light option or
specificaly turn OFF some option for that light_source.
In this case, you don't need to use light fading. A plain non-fading
light is OK.
>
> //Reflector
> cylinder {<0,0,-30> <0,0,30> 10 open clipped_by {box {<-30,-30,-40> <0,30,40>
> inverse} }
> texture {pigment {color rgb<1,1,1>} finish {emission 0 ambient 0 reflection
> 1 diffuse 0 } }
> photons {target reflection on refraction off collect on}
> }
>
> Thanks
>
>
Your clipping box is exactly the same hight as your cylinder. This leads
to coincident surfaces, in some cases, even when using "open". Make your
box a little smaller, or the cylinder a little taller.
cylinder {<0,0,-30.001> <0,0,30.001> 10 open...
Make absolutely sure that there are no transparent object in front of
the light. If there is any, it need photons{pass_through} to be added.
The extinction is specific to the scattering media. It controls the
amount of incoming light that is absorbed by the media. It's default
value is 1 and any other value is not physically correct. In case such
as this one, it can be set lower, even down to zero, to ignore the
absorption and to be able to show the full path of the light and
photons. This affect ONLY light and photons, the background remains
unaffected by this setting.
Just as a test, try this for your reflection:
reflection{rgb<1,0,0>}
This will make a reflector that reflect only the red, that should make
it more visible. You may also unrealistically increase the reflection
like this:
reflection{rgb<4,0,0>}
Alain
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