[Radiance-general] gloss and area light source rendering problem

[Yun-Xian Ho]

Thanks for the speedy and helpful responses, Jack and Greg. It's good to 
know that there is nothing necessarily wrong with my code, just my 
perception. :) This also suggests that I should probably not make these 
surfaces "shiny." In response to Jack's P.S., the geometry is designed 
to investigate gloss and the perception of bumpiness, where bumpiness is 
defined as the variance of bump heights (ellipsoid depths). I was 
inspired by a variety of skin imperfections...and clusters of shiny 
raspberries. If course, if anyone has any better suggestions of modeling 
"macro-bumpiness," I'd be happy to hear them.

--xian

Gregory J. Ward wrote:

> Hi Xian,
>
> Adding to Jack's comments, I think you will see what appears as noise  
> no matter what you do.  The minification that happens on multiple  
> reflections makes your light source into a dot.  In other words, in  
> the reflection of one sphere you see more spheres.  The miniaturized  
> image of the light source becomes a microminiaturized reflection in  
> the reflected spheres, and micromicrominiaturized in the reflection  
> of reflection of other spheres.  These will look like noise to your  
> eye, but that's what the real scene would look like, also.
>
> -Greg
>
>> From: Yun-Xian Ho <yunxian.ho at nyu.edu>
>> Date: May 22, 2006 4:50:51 AM PDT
>>
>> Hi All,
>>
>> I have been having problems rendering a glossy bumpy surface  
>> composed of intersecting ellipsoids illuminated under a rectangular  
>> light source. The image appears to contain some random point source  
>> reflections on the surface in addition to the direct reflection of  
>> the area light.
>>
>> To view the rendered image, see: http://homepages.nyu.edu/~yxh201/ 
>> bumpysurftest.jpg.
>>
>> The bumpy surface is made of the following material:
>> void plastic gray_plastic
>> 0
>> 0
>> 5 .2 .2 .2 .1482 0
>>
>> and a 30x24 flat rectangular light source is defined as:
>> void light bright
>> 0
>> 0
>> 3 25 25 25
>>
>> I use the following parameters to render the scene:
>> -ab 2 -aa .08 -ad 1024 -as 512 -av .2 .2 .2 -sj 1 -st .01 -dj 1 - ds .05
>>
>> Any suggestions to clean up the "noise" in the image? Much thanks...
>>
>> --xian
>