Hi,

I have this blob made up of 5000 glass spheres inside a spherical HDR. 
The result is attached. I turned on photons, but can't get any caustics 
to appear.
MegaPOV returns an error: Slab Building warning: Could not save photon 
map - no photons!

The blob object hass these propertis:
sturm
texture {
   pigment { color rgbt 1 }
   finish {
     ambient 0
     diffuse 0
     reflection { 0.1, 1.0 fresnel on }
     conserve_energy
   }
}
interior {
   ior 1.5
   fade_distance 1.1
   fade_color <0.11, 0.1, 0.3>
}
photons{
   target Radius1/2
   refraction on
   reflection on
}

I can't find out what is wrong. Any suggestions are welcome.

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Attachments:
Download 'newt.jpg' (56 KB)

Preview of image 'newt.jpg'

Maurice nous apporta ses lumieres ainsi en ce 2005-01-02 04:37... :

> Hi,
>
> I have this blob made up of 5000 glass spheres inside a spherical HDR. 
> The result is attached. I turned on photons, but can't get any 
> caustics to appear.
> MegaPOV returns an error: Slab Building warning: Could not save photon 
> map - no photons!
>
> The blob object hass these propertis:
> sturm
> texture {
>   pigment { color rgbt 1 }
>   finish {
>     ambient 0
>     diffuse 0
>     reflection { 0.1, 1.0 fresnel on }
>     conserve_energy
>   }
> }
> interior {
>   ior 1.5
>   fade_distance 1.1
>   fade_color <0.11, 0.1, 0.3>
> }
> photons{
>   target Radius1/2
>   refraction on
>   reflection on
> }
>
> I can't find out what is wrong. Any suggestions are welcome.
>
> ------------------------------------------------------------------------
>
What are the photons settings for the floor? Does it collect them?

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Alain wrote:
> Maurice nous apporta ses lumieres ainsi en ce 2005-01-02 04:37... :
> 
>> Hi,
>>
>> I have this blob made up of 5000 glass spheres inside a spherical HDR. 
>> [blabla...]
>> }
>>
>> I can't find out what is wrong. Any suggestions are welcome.
>>
>> ------------------------------------------------------------------------
>>
> What are the photons settings for the floor? Does it collect them?

The floor:

plane{ <0,1,0>, 0
   texture{
     pigment{checker color rgb<1,1,1>*1.2 color rgb<1,1,1>}
     finish{ambient 0.1 diffuse 0.8 metallic reflection{0.9}}
   }
   no_radiosity
}

It has no photons section...

-- 
Maurice

Welcomes everybody to the fifth year of the century.

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Maurice nous apporta ses lumieres ainsi en ce 2005-01-02 10:30... :

> Alain wrote:
>
>> Maurice nous apporta ses lumieres ainsi en ce 2005-01-02 04:37... :
>>
>>> Hi,
>>>
>>> I have this blob made up of 5000 glass spheres inside a spherical 
>>> HDR. [blabla...]
>>> }
>>>
>>> I can't find out what is wrong. Any suggestions are welcome.
>>>
>>> ------------------------------------------------------------------------ 
>>>
>>>
>> What are the photons settings for the floor? Does it collect them?
>
>
> The floor:
>
> plane{ <0,1,0>, 0
>   texture{
>     pigment{checker color rgb<1,1,1>*1.2 color rgb<1,1,1>}
>     finish{ambient 0.1 diffuse 0.8 metallic reflection{0.9}}
>   }
>   no_radiosity
> }
>
> It has no photons section...
>
No photons section = collect on  target off  OK
Then, it may be that the high reflection value (0.9) make them almost 
invisible. The more reflective a surface is, the less it will show 
photons effects. That's the main reason why it's recomended to set 
collect off for highly reflective surfaces.

Alain

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> Then, it may be that the high reflection value (0.9) make them almost
> invisible. The more reflective a surface is, the less it will show
> photons effects. That's the main reason why it's recomended to set
> collect off for highly reflective surfaces.

Additionally, check if max_trace_level for the photons is high enough to
actually reach the plane. If the glass object has lots of holes in it, a
photon won't pass through, but rather get stuck somewhere along the way.
Note that you can define different max_trace_level for photons and the
actual raytraced rays, but I'm unsure if they use the same keyword... You'd
have to look at the docs for that.

Regards,
Tim

-- 
"Tim Nikias v2.0"
Homepage: <http://www.nolights.de>

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Does your light_source emit photons?

-S
5TF!

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stm31415 wrote:
> Does your light_source emit photons?
> 
> -S
> 5TF!
> 
There is no lightsource as such. This is a scene running on radiosity. 
The light is caused by a HDR image.

-- 
Maurice

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That explains everything. Only lightsources cause photons, if you'd want to
have caustics created by radiosity, you'd have to use ridiculously high
settings for the tracing depth.

A workaround would be to do a two-pass render. On the first pass, you only
render with a lightsource and photons, which you save to disk using
save_file in the photons-block. On the second pass, you render using
radiosity, but instead of placing an actual lightsource, you just load the
photons using load_file. You'd get the photons without the lightsource that
way.

-- 
"Tim Nikias v2.0"
Homepage: <http://www.nolights.de>

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Alain wrote:
> Maurice nous apporta ses lumieres ainsi en ce 2005-01-02 10:30... :
> 
>> Alain wrote:
>>
>>> Maurice nous apporta ses lumieres ainsi en ce 2005-01-02 04:37... :
>>>
>>>> Hi,
>>>>
>>>> I have this blob made up of 5000 glass spheres inside a spherical 
>>>> HDR. [blabla...]
>>>> }
>>>>
>>>> I can't find out what is wrong. Any suggestions are welcome.
>>>>
>>>> ------------------------------------------------------------------------ 
>>>>
>>>>
>>> What are the photons settings for the floor? Does it collect them?
>>
>>
>>
>> The floor:
>>
>> plane{ <0,1,0>, 0
>>   texture{
>>     pigment{checker color rgb<1,1,1>*1.2 color rgb<1,1,1>}
>>     finish{ambient 0.1 diffuse 0.8 metallic reflection{0.9}}
>>   }
>>   no_radiosity
>> }
>>
>> It has no photons section...
>>
> No photons section = collect on  target off  OK
> Then, it may be that the high reflection value (0.9) make them almost 
> invisible. The more reflective a surface is, the less it will show 
> photons effects. That's the main reason why it's recomended to set 
> collect off for highly reflective surfaces.

I think you might be right. When I switch off the reflective finish of 
the floor I see a hint of caustics on the floor. Is there any way to 
increase the strenght of the caustics? Can't seem to find anything in 
the manual that promises to do this. I found the caustics keyword for 
interior but whatever value I use it doesn't seem to give the right effect.

-- 
Maurice

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Do what Tim said, using saved data. Radiosity does give very pale caustics,
but if you use the two pass method they will be clear and bright.

-S
5TF!

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