[Radiance-general] Modelling an artificial sky : help needed

[jeando]

Thanks to you two

I'll try your suggestions.

JeanDo

Greg Ward a écrit :
> Hi Ljubica,
>
> I just want to add to what Thomas wrote.  Quoting your webpage:
>
>> Materials are basic :
>> walls are mirrors (80% reflexion - mirror material)
>> ceiling is translucent (60% transmission all diffuse, trans material)
>> floor is gray (60% reflexion, plastic material)
>> half-sphere is blue plastic
>
> Since your trans surface blocks visibility of the light sources, I 
> wouldn't recommend using the mirror type for this at all.  I'd just 
> use an 80% reflective metal material (pure specular) and let the 
> interreflection calculation handle it.  I don't think an illum is 
> suitable, due to the high variance in luminance over the surface of 
> each panel.
>
> I'm actually quite surprised at how bad these results look.  I think 
> something else must be going on that I don't understand, like leaks at 
> the sides of the structure.  Anyway, try it without the mirror type 
> and see if that helps.
>
> Your calculation time could probably be improved without too much loss 
> in accuracy by using a glow material for the cylindrical light sources 
> -- set the distance limit to something like 4 times the size of one of 
> your light panel widths.
>
> Finally, I don't think a pure diffuse translucent material can have a 
> transmission over 50%.
>
> Best,
> -Greg
>
>> From: jeando <jdlenard at deluminaelab.com>
>> Date: October 22, 2008 2:04:22 AM PDT
>>
>> Hi,
>>
>> We are building an artificial sky for an architecture school where we 
>> teach, and before starting we prepare a Radiance model, to simulate 
>> the interior of the artificial sky. The idea is to help us to choose 
>> the right bulbs, the ceiling, etc.
>>
>> To simulate the overcast sky (Moon and Spencer) distribution in 
>> Radiance we made walls of mirror material and ceiling is filled with 
>> fluorescent tubes (very close to one another) and covered with 
>> translucent material. Then we tried to render few images of interior, 
>> with  several sets of rendering parameters, but final images still 
>> aren't good enough with a lot of spots.
>>
>> Please see our results on 
>> http://docs.google.com/Doc?id=dfvbdbg3_13f66n99kx
>>
>> Does anyone on the list have an experience with similar modelling, 
>> where mirror objects are included?
>> Why do we get strange spots on the floor even when ambient parameters 
>> are really high?
>> What combination of parameters may lead us to good image, for 
>> acceptable rendering time?
>>
>> Thanks in advance,
>> Ljubica, JeanDo, Marija
>
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