Le 17-05-01 à 02:50, Thomas de Groot a écrit :
> On 30-4-2017 18:30, Alain wrote:
>> Le 17-04-30 à 07:05, Thomas de Groot a écrit :
>>> On 30-4-2017 9:48, Thomas de Groot wrote:
>>>> In fact, the differences are more subtle. For the cube, compare the
>>>> shadows of dragon and egg: their edges show the stone's 
>>>> translucency. In
>>>> my next render I hope to show this better.
>>>>
>>>
>>> In this render:
>>>
>>> - Dragon: no SSLT
>>> - Floor: no SSLT
>>> - Cube: SSLT with 5*translucency vector (was 2* in earlier example)
>>> - Egg: SSLT with 3*translucency vector (was 2* in earlier example)
>>>
>>> The cube is showing markedly more translucency in the shadows cast on
>>> it. I see not much difference in the egg, although if I increase the
>>> translucency exaggeratedly (*100 for instance) the effect becomes
>>> distorted.
>>>
>>> Question: In the wiki about SSLT it is said: "The effect doesn't scale
>>> with the object". Does this mean that SSLT works in the same way as a
>>> scattering media where the amount of scattering has to be compensated
>>> for the amount of media object's scale? It appears so to me at least
>>> although this is not mentioned in the wiki.
>>>
>>
>> It does work similarly to medias, both emissive, absorbing and 
>> scattering.
>>
>> So, if you scale your scene by 10 and want SSLT to look the same, then
>> you need to multiply your SSLT vector by 10. Alternately, you can
>> increase mm_per_unit by the same amount in the global_settings block.
>>
> 
> OK. Only difference would be that with scattering media (for instance) 
> you have to /divide/ the scattering vector by the scale of the container 
> to get the same result, but I get the point indeed.
> 
> I am a bit wary about the mm_per_unit and prefer not to touch it too 
> much, especially if different objects have different scales.
> 

You should set it according to the overall scale of your scene.
The default of 10 mean 1 POV unit = 1 cm. Set it to 1000 if your scale 
is 1 POV unit = 1 m, and 25.4 for 1 inch = 1 POV unit.

In my suggestion, it would make a scene scalled in cm work in mm. So, 
you can change mm_per_unit from it's default of 10 to 1 to reflect the 
change in overall scale.

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