[Radiance-general] Strange behaviour with mixed material

[Greg Ward]

Hi Santiago,

Giulio kindly shared his tutorials and I haven't gotten around to putting them onto radiance-online.org, mostly because I don't know how to modify the website anymore since it was updated.  However, I have uploaded this particular tutorial for you to:

	http://www.anyhere.com/gward/pickup/giulio_mirror.tar.gz

However, this is really a situation that didn't occur to me, where you have indirect rays coming from the opposite side.  I see now that I should modify a test in the m_mirror.c routine to account for this case.  I will send you a modified version of this file in hopes that you can rebuild and test it for me.

Cheers,
-Greg

> From: Santiago Torres <Santiago.Torres at arup.com>
> Date: June 3, 2016 1:10:50 PM PDT
> 
> Dear all,
>  
> I’m trying to define a mixfunc material to modify a mirror definition, so I can create holes (horizontal bands in this case) in the mirror. This was explained in an old tutorial by G. Antonutto, which now seems lost (at least I couldn’t find it online… pillo?).
>  
> The complete definition is like this:
>  
> ## metal
> void metal metal_01
> 0
> 0
> 5 .8 .8 .8 .05 0
>  
> ## mix the metal with void to create holes
> void mixfunc strip
> 4 metal_01 void 'if(sin(Pz/10),0,1)' .
> 0
> 0
>  
> ## alter the reflectance of mirror, reflectance is 0% for holes
> void brightfunc band
> 2 'if(sin(Pz/10),0,1)' .
> 0
> 0
>  
> ## mirror attached to the metal surface with holes
> band mirror mix_01
> 1 strip
> 0
> 3 .9 .9 .9
>  
>  
> If I create a cube with the “mix_01” material, it looks as expected. Horizontal bands of void in the mirror let the direct light through and the reflected light is also in matching stripes.
>  
> However, with the diffuse calculation, light doesn’t seem to get through the void part. For example, if I measure irradiance inside the cube with only a glow source outside, I get zero.
>  
> The strangest part is that if I look at the model in rvu, it looks fine and there is diffuse light inside… unless I set –aa 0!!!
>  
> All other settings seem to make no difference (with ab > 0, of course).
>  
> Rpict behaves like rtrace, no diffuse light through.
>  
> I’ve tried setting all rtrace parameters to the rvu defaults (including dr 0), but the result is still nothing.
>  
> I’m sure there is an explanation, which is possibly that the material is just too weird, but I’m still confused by the strange difference in behaviour between rtrace/rpict and rvu…
>  
> Any ideas?
> Thanks!
> Santiago
>  
> ____________________________________________________________
> Electronic mail messages entering and leaving Arup  business
> systems are scanned for acceptability of content and viruses
> 
> _______________________________________________
> Radiance-general mailing list
> Radiance-general at radiance-online.org
> http://www.radiance-online.org/mailman/listinfo/radiance-general
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.radiance-online.org/pipermail/radiance-general/attachments/20160603/321da140/attachment.html>