[Radiance-general] mirror material ignoring modifier in virtual source calculations

[Greg Ward]

Hi Rioboo,

Your definition looks correct to me.  What different conditions are you using to make this determination?

1) Do you change the angle of the sun?  This is the only way to test different angles on the mirror, since the sun is a collimated source of light.

2) When you change the solar angle, do you move your point or at least ensure that it remains in the reflected beam?  If it sees sunlight directly as well, you will need to look for variation in the 8-80% that is reflected (depending on angle).

3) Are you sure your mirror surface normal faces outwards?  If it faces inwards, like most windows in Radiance, then the mirrored sources will only happen on the interior.

Cheers,
-Greg

> From: goodriver laurus <rioboo at gmail.com>
> Date: June 13, 2016 2:29:16 AM PDT
> 
> 
> Dear Greg,
> 
> Many thanks for for quick response. I am trying to use a modified mirror like the one posted on 17 March 2008 in order to emulate the angular-dependent reflections from a glass:
> 
> void glass glass_alt_mat
> 0
> 0
> 3 0.96 0.96 0.96
> 
> void brightfunc glass_angular_effect
> 2 A1+(1-A1)*(exp(-5.85*Rdot)-0.00287989916) .
> 0
> 1 0.08
> 
> glass_angular_effect mirror glass_mat
> 1 glass_alt_mat
> 0
> 3 1 1 1
> 
> I use this material to quantify in a top view the illuminance on the ground due to reflected light from vertical windows (therefore not looking at the glass, but just at the reflections). The calculation is been done with rpict -i -ab 0 -dr 1. I have also tried other values for the parameters but the results are the same.
> 
> I would expect the reflections to vary in value depending on the angle of incidence on the glass. However, all reflections seem to be of the same intensity, actually 100% reflective like in an ideal mirror.
> I wonder if the issues I am having may have to do with the way I am using rpict or if there is a more fundamental error. I have tried testing this issue in Radiance 4.2 for Windows to see if could have to do with the platform or with recent issues with the m_mirror routine, as posted a few days ago, but the results are again the same.
> 
> Thanks and best regards,
> 
> Rioboo
> Hi Rioboo,
> 
> It helps when you give a specific example.  What is your material definition, and what is it doing that disagrees with your expectations?
> 
> The mirror material will ignore its modifiers in the case when you have given an alternate material type.  This will be called instead when viewed directly.  The modifiers to the mirror itself will only be used for calculating the virtual source contributions.
> 
> Best,
> -Greg
> 
> > From: goodriver laurus <rioboo at gmail.com>
> > Date: June 12, 2016 4:16:03 PM PDT
> > 
> > Dear all,
> > 
> > I am currently having problems using mirror materials with brightfunc modifiers for virtual source calculations. The mirror material seems to ignore the modifier. I've seen in recent post that there seems to be a bug with in the m_mirror routine and I wonder if that is the problem or if it could be something else.
> > 
> > Thanks,
> > 
> > rioboo
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