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Dear all,
I'm using povray to model the focusing and retro-reflection of glass
microspheres, so a pretty simple set up really. The problem that I am having is
that the areas where the photon density is high and the situations where the
spheres are re-imaging the light source at the camera (i.e the plane is near the
focal point of the shperical lens and the camera and light source are on the
same axis) the image saturates completely.
Two questions. 1./ Can the levels of the image be scaled to use the high
brightness areas from the photon regions?
2./ Are there any programs to extract the data from the photon map for analysis
elsewhere?
Below is a simple scene to demonstrate the saturation
// ----------------- Includes and declarations -------------------------------
#include "colors.inc"
#include "textures.inc"
#declare AMBILIGHT = 0.1;
// ---------------- Global Settings -----------------------------------
global_settings {
photons {
//count 2000000
//radius 10
spacing 0.01
autostop off
jitter 0.4
save_file "photon map.ph"
//load_file "photon map.ph"
adc_bailout 0.0000153
max_trace_level 10
}
}
// ---------------- Cameras --------------------------------------------
#declare cam1 = camera { orthographic
location <5, 10, 0 > //camera should be placed above
the origin 5 units//
look_at <5, 0, 0>
sky y //looking back at the origin
//right <1.33, 0, 0>
//angle 10
}
camera {cam1}
// ------------------ Light Sources ----------------------------//
#declare light1 = light_source { <10, 3, 0>
colour White*1 //light source colour and power
//area_light <0,1,0>, <0,0,1>, 3, 3 //area light
cylinder
radius 2
falloff 2.2
parallel // All rays are launched parallel
point_at <5, 0, 0> // position vector that light rays are launched at
photons{
reflection on
refraction on
}
}
#declare light2 = light_source { <4, 5, 0>
colour <0.4,0.6,0.8>*0.1 //light source colour and power
//area_light <0,1,0>, <0,0,1>, 3, 3 //area light
cylinder
radius 5
falloff 5.1
parallel // All rays are launched parallel
point_at <4, 0, 0> // position vector that light rays are launched at
photons{
reflection on
refraction on
}
}
light_source {light1}
light_source {light2}
// ------------------ Objects -------------------------//
plane { y, 0
texture { pigment { rgb <0.5, 0.5, 0.7> } }
photons{
reflection on
collect on
}
finish { diffuse 1.0
specular 0.0
ambient 0.0
}
}
#declare Sradius = 0.5;
sphere {<0,Sradius,0>, Sradius
texture { pigment { rgbt 1 }
}
interior {
ior 1.8
}
finish{ ambient AMBILIGHT
diffuse 0
reflection {0, 1.0
fresnel on}
conserve_energy
}
photons { target 1.0
refraction on
reflection on
collect off
}
translate <4.5,0,0>
}
#declare Sradius2 = 1;
sphere {<0,Sradius2,0>, Sradius2
texture { pigment { rgbt 1 }
}
interior {
ior 1.5
}
finish{ ambient AMBILIGHT
diffuse 0
reflection {0, 1.0
fresnel on}
conserve_energy
}
photons { target 1.0
refraction on
reflection on
collect off
}
translate <5.5,0.0,2>
}
Post a reply to this message
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> Dear all,
>
> I'm using povray to model the focusing and retro-reflection of glass
> microspheres, so a pretty simple set up really. The problem that I am having is
> that the areas where the photon density is high and the situations where the
> spheres are re-imaging the light source at the camera (i.e the plane is near the
> focal point of the shperical lens and the camera and light source are on the
> same axis) the image saturates completely.
>
> Two questions. 1./ Can the levels of the image be scaled to use the high
> brightness areas from the photon regions?
>
> 2./ Are there any programs to extract the data from the photon map for analysis
> elsewhere?
>
The saturation comes from the clipping when the intensity becomes to
great to be represented in the used image format.
If you use version 3.6, it's possible to add a darkening filter in front
of the camera. A simple thin box with a gray filtering pigment. Be sure
to set it with photons{collect off} as you don't want any photon showing
on it.
You can also reduce the strenght of the light_source.
If you use version 3.7, you can output the image in a high dynamic range
format.
For the point 2, I don't know of any.
Alain
Post a reply to this message
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On 28/05/2011 01:07, Alain wrote:
>> Dear all,
>>
>> I'm using povray to model the focusing and retro-reflection of glass
>> microspheres, so a pretty simple set up really. The problem that I am
>> having is
>> that the areas where the photon density is high and the situations
>> where the
>> spheres are re-imaging the light source at the camera (i.e the plane
>> is near the
>> focal point of the shperical lens and the camera and light source are
>> on the
>> same axis) the image saturates completely.
>>
>> Two questions. 1./ Can the levels of the image be scaled to use the high
>> brightness areas from the photon regions?
>>
>> 2./ Are there any programs to extract the data from the photon map for
>> analysis
>> elsewhere?
>>
>
> The saturation comes from the clipping when the intensity becomes to
> great to be represented in the used image format.
>
> If you use version 3.6, it's possible to add a darkening filter in front
> of the camera. A simple thin box with a gray filtering pigment. Be sure
> to set it with photons{collect off} as you don't want any photon showing
> on it.
>
> You can also reduce the strenght of the light_source.
>
> If you use version 3.7, you can output the image in a high dynamic range
> format.
>
>
> For the point 2, I don't know of any.
>
>
> Alain
Thanks Alain, I'll get version 3.7 and try the hdr options
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