[Radiance-general] Preview error - unknown object type "ashik2"

[Georg Mischler]

So does that mean that the right sphere in the slideshow reflects
26% more light on average than the left one?

void plastic2 mat1
4 0 1 0 .
0
6 .3 .7 .5 .26 .1 .02

void ashik2 mat2
4 0 1 0 .
0
8 .3 .7 .5 .26 .26 .26 150 5000

Its hard to tell from the images, but it does appear slightly brighter.

Cheers
-schorsch


Am 2016-04-22 23:15, schrieb Greg Ward:
> Yes, unlike the other Radiance materials, you need to consider the sum
> of specular and diffuse components to determine whether you are within
> physical limits.  The standard "plastic" and "metal" (likewise
> "plastic2" and metal2") simply make a binary choice between colored
> and uncolored highlights.  The "ashik2" type allows you full control.
> I don't know what materials this is useful, however.
> 
> Cheers,
> -Greg
> 
>> From: Georg Mischler <schorsch at schorsch.com>
>> Subject: Re: [Radiance-general] Preview error - unknown object type 
>> "ashik2"
>> Date: April 22, 2016 1:31:40 PM PDT
>> 
>> Very interesting, thanks.
>> 
>> My conclusions go like this:
>> 
>> * The useful range of the exponents seems to be between 0 (fully
>>  diffuse and 10000 (mirror-like). Between 5 and 100 looks like the
>>  most interesting range.
>> 
>> * To create a plastic-like appearance, the specular reflection should
>>  be desaturated.
>> 
>> * For a metallic appearance, the specular and diffuse reflections
>>  should have a similar tint.
>> 
>> Remaining questions:
>> 
>> * What happens when specular and diffuse colors are vastly different?
>>  I'm expecting something rather psychedelic... Do actual materials
>>  like that exist?
>> 
>> * Do the diffuse and specular color values depend on each other?
>>  Eg. should their sum be less than 1?
>> 
>> 
>> Cheers
>> -schorsch
>> 
>> 
>> Am 2016-04-22 17:10, schrieb Greg Ward:
>>> Hi Schorsch,
>>> The Ashikhmin-Shirley reflectance model is a kind of anisotropic 
>>> Phong
>>> model made physically plausible.  It's main advantage over the
>>> standard anisotropic model in Radiance is that it includes a Fresnel
>>> modifier, which I use for perfectly smooth surfaces.  Best to read
>>> their original paper:
>>> 	www.cs.utah.edu/~shirley/papers/jgtbrdf.pdf
>>> I added this model to Radiance a few years back with help from 
>>> Nicolas
>>> Bonneel, as we were trying to run some comparisons.  Peter
>>> Apian-Bennewitz also had requested it, so it seemed worthwhile to 
>>> add.
>>> Cheers,
>>> -Greg
>>>> From: Georg Mischler <schorsch at schorsch.com>
>>>> Subject: Re: [Radiance-general] Preview error - unknown object type 
>>>> "ashik2"
>>>> Date: April 21, 2016 10:34:16 PM PDT
>>>> Is there any documentation on how to actually use this material?
>>>> So far it is only mentioned in a release note and on some 
>>>> presentation
>>>> slides, but not explained at all.
>>>> What are eg. useful input values for "specular power"?
>>>> Cheers
>>>> -schorsch
>>>> Am 2016-04-21 18:39, schrieb Greg Ward:
>>>>> The '_unknown object type_' error is caused by reading in a frozen
>>>>> octree (generated with "oconv -f") on an older version of Radiance,
>>>>> before this type was added. You need to update your copy of 
>>>>> Radiance
>>>>> from https://github.com/NREL/Radiance/releases [1]
>>>>> Chris has the right advice on X11.
>>>>> Cheers,
>>>>> -Greg
>> 
>> 
>> --
>> Georg Mischler  --  simulations developer  --  schorsch at schorsch 
>> com
>> +schorsch.com+  --  lighting design tools  --  
>> http://www.schorsch.com/
>> 
>> 
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-- 
Georg Mischler  --  simulations developer  --  schorsch at schorsch com
+schorsch.com+  --  lighting design tools  --  http://www.schorsch.com/