[Radiance-general] Integrated photon mapping and material roughness

[Schregle Roland HSLU T&A]

On Sun, 02 Aug 2015 12:21:22 +0200, Martin Klingler
<martin.klingler at gmx.at> wrote:

> Hello experts,
>
>  playing around with the new integrated photon mapping I met the  
> following strage effect.

> Now I change to the radiance HEAD from the 4th July. I use the same  
> geometry and the following rad file:

> But when I change to the roughness 0.1 I get this output:  
> https://dl.dropboxusercontent.com/u/27495200/RoughnF.jpg
>
> I already tried differend setting for the bandwidth parameter but the  
> were no fundamental chages.

Hi Martin,

this is indeed weird, and resembles irradiance cache extrapolation  
artefacts, even though I understand ambient rays aren't even traced with  
INDIRECT=0, nor do they have to be if there are no other diffuse surfaces,  
so none of that should be going on.

Is the observed pattern (which resembles a Fresnel lens) from the LED's  
IES file? That would explain why the "jaggies" are also visible on the  
left edge of the mirror, where no photons reside. What worries me more is  
that the
lighting levels are too high.

The code has changed substantially in the course of this year, so it's  
hard to pinpoint the root cause offhand. I'll try reproducing this with a  
"point" source to check what's up. Failing that, could you send me the LED  
definition with IES file for testing?

Thanks & best regards,

--Roland


-- 
Dr. Roland Schregle
Senior Research Associate

Lucerne University of Applied Sciences and Arts
School of Engineering and Architecture
CC Envelopes and Solar Energy (EASE)
www.hslu.ch/ccease

T direct: +41 41 349 36 26 (New)
roland.schregle at hslu.ch

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