Alain napsal(a):
> Sylvain Dubé nous illumina en ce 2008/04/23 15:20 -->
>> Hi
>> I'm looking to simulate a doublet of lens. I have a problem with 
>> photons when I
>> take the two lens separately. Photons are stopped in the interface.
>> For now, I'm trying to construct my doublet in one object but I don't 
>> know if
>> it's the best way.
>>
>> For exemple, this is my lens
>>
>> #declare lentille = merge
>> {
>>  intersection
>>  {
>>   cylinder{<0,0,16>,<0,0,1>,25.4}
>>   sphere{<0,0,15-83.2>,83.2}
>>   sphere{<0,0,71.1+3>,71.1}
>>   hollow
>>   pigment {Clear } interior { ior n1}
>>   photons {target reflection off refraction on collect off}
>>  }
>>  intersection
>>  {
>>   sphere{<0,0,247.7>, 247.7}
>>   cylinder{<0,0,7.7>,<0,0,-1>,25.4}
>>   hollow
>>   pigment {Clear } interior { ior n11}
>>   photons {target reflection off refraction on collect off}
>>  }
>> }
>>
>> In this way, are my ior conserved in each part?
>> Does there another solution?
>>
>> Thank you
>>
>> Sylvain
>>
>>
> "hollow" is totaly, completely and uterly useless in your case, as your 
> lense don't contain any media.
> 
> Make sure that there is a slighy gap between the two components to 
> prevent any coincident surfaces. Also, make sure that the components 
> never intersect as they do in your sample. It's unrealistic. The 
> behaviour is also hard to predict.
> 
> You don't need to use a merge, a simple union is good enough.
> It's beter to place the photons block in the union rather than to each 
> individual component. If you use the same texture for all element, it's 
> also beter to place your texture in the union and not in each component 
> definition.
> 
> What is your max_trace_level? It default to 5, and your doublet counts 4 
> surfaces. If your photons ever encounter even 1 surface prior to 
> entering the double lense, they won't get out. You must count 2 steps 
> for each transparent object, one for any reflection and one for the 
> surface that will receive the photons. If you are unsure, take a larger 
> value than what you guessed, up to 256.
> 
> Your solution may be as simple as adding:
> 
> global_settings{max_trace_level 7}
> 
> Make it the first line of your scene.
> 
> I've tested your sample, after moving the elements so that they no 
> longer overlap, and with max_trace_level of 6.
> The provided lense have a prety short focal lenght. Maybe your receiving 
> surface was set to far away and the photons got to dispersed to still be 
> visible...
> 
If you move the objects slightly apart you will get a visible gap. I 
think the refraction works this way: It remembers the objects it is in 
and uses the IOR of the last object entered and not escaped. Not sure 
how this applies to a union but merge will cause problems.

-- 
the ultimate time-killer:
+a0.0 +am2 +r9

Johnny D

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