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

[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/
> 
> 
> _______________________________________________
> Radiance-general mailing list
> Radiance-general at radiance-online.org
> http://www.radiance-online.org/mailman/listinfo/radiance-general