[Radiance-general] gloss specifications to roughness/specularity

[Matt Franks]

Jack-

There is a paper in the SIGGRAPH 2000 proceedings called "Towards a
Psychophisically-Based Light Reflection Model for Image Synthesis" by
Pellacini, Ferwerda, and Greenberg that looks at using visually
evaluated measurements to formulate a model for gloss.

They relate their visually measured parameters to the phyically based
parameters used in Radiance.  I'm not sure how it relates to other gloss
parameters or how it would actually work if you tried to use it (I
haven't), but it might be worth a look.

Let me know if you can't get hold of the paper...

-Matt
 

-----Original Message-----
From: radiance-general-bounces at radiance-online.org
[mailto:radiance-general-bounces at radiance-online.org] On Behalf Of Jack
de Valpine
Sent: Tuesday, February 07, 2006 11:24 AM
To: Radiance general discussion
Subject: Re: [Radiance-general] gloss specifications to
roughness/specularity

Hi Greg,

Well I was pretty sure it was wishful thinking. I guess I had been
hoping that with some understanding of the gloss appearance metric there
might be a way back into at least some meaningful ballpark for roughness
and specularity.

Ok, well on a related note, other than a full BRTD what would be the
best way to simulate a so-called metalic paint, that is a paint that
includes metal flakes...? Is this still best qualified as a plastic or
should it in fact be a metal?

-Jack

Gregory J. Ward wrote:
> Hi Jack,
>
> I know of no way to take standard gloss measurements and convert them 
> into something that is physically meaningful, since they combine 
> specularity with roughness to obtain a single value at a specific
angle.
>
> -Greg
>
>> From: Jack de Valpine <jedev at visarc.com>
>> Date: February 6, 2006 8:49:29 AM PST
>>
>> Hi All,
>>
>> I am curious if there is a way to estimate material 
>> roughness/specularity based on gloss specifications. PPG provides a 
>> gloss range for its factory applied metal coatings (such as DURANAR).
>> The way they indicate this is as a range at a given measurement 
>> angle, for example:
>> 25% to 35%  at 60 degrees
>> This is according to the ASTM-D523 - Specular Gloss.
>>
>> Is there some way to make this meaningful as a part of a radiance 
>> material specification?
>>
>> Thanks,
>>
>> -Jack
>
> _______________________________________________
> Radiance-general mailing list
> Radiance-general at radiance-online.org
> http://www.radiance-online.org/mailman/listinfo/radiance-general
>
>

--
# Jack de Valpine
# president
#
# visarc incorporated
# http://www.visarc.com
#
# channeling technology for superior design and construction



_______________________________________________
Radiance-general mailing list
Radiance-general at radiance-online.org
http://www.radiance-online.org/mailman/listinfo/radiance-general
____________________________________________________________
Electronic mail messages entering and leaving Arup  business
systems are scanned for acceptability of content and viruses