[Radiance-general] Strange behaviour with mixed material

[Randolph M. Fritz]

I've put up the "Asphalt" example at
http://www.radiance-online.org/learning/tips-tricks/Asphalt. Please let me
know if it looks OK.

Randolph

On Tue, Jun 7, 2016 at 7:35 AM, Santiago Torres <Santiago.Torres at arup.com>
wrote:

> Thanks due to Kanae Hagiwara, from our Tokyo office, who found the problem!
>
>
>
> And to Greg, of course, for finding the solution!
>
>
>
> S.
>
>
>
>
>
> *From:* Gregory J. Ward [mailto:gregoryjward at gmail.com]
> *Sent:* 06 June 2016 17:25
> *To:* Greg Ward
> *Cc:* Radiance general discussion
> *Subject:* Re: [Radiance-general] Strange behaviour with mixed material
>
>
>
> Just a quick follow-up.  This was indeed a bug in the m_mirror routine,
> which is now sorted out.  The next distribution should fix it.
>
>
>
> Thanks, Santiago!
>
>
>
> -Greg
>
>
>
> *From: *Greg Ward <gward at lmi.net>
>
> *Date: *June 3, 2016 1:38:53 PM PDT
>
>
>
> 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
>
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