[Radiance-general] Annual simulations + BSDF

[Greg Ward]

Hi Andrew,

I guess I should write a program or script to create a BTDF file for  
an arbitrary shading system.  It's not particularly difficult to do  
this using rtcontrib, but I need to find time to do it.  The next  
couple of weeks are crazy between the workshop and the HDR Imaging  
book deadline, so I don't think I'll get to it before then.  I won't  
be much help with your deadline, unfortunately.

-Greg

> From: Andrew McNeil <andrew.mcneil at arup.com>
> Date: October 16, 2009 9:34:13 AM PDT
>
> Hi Greg,
>
> Thanks for your reply.  Unfortunately I’m not going to Boston.  Now  
> I have yet another reason to wish I was going.
>
> I’m glad you’ve been able to further develop the 3-phase method.  I  
> see increasing demand for this type of analysis for complex façade  
> shading systems.  This is the fourth time I’ve started down this  
> route – the other three times stopped abruptly for various reasons.   
> Twice before with panelite products and once with an engineered  
> scattering window film.  The email I sent yesterday was a  partially  
> complete left in my drafts folder from two months ago - the last  
> time this I was looking into this approach.
>
> I don’t have a hard deadline yet.  The goal for now is to develop a  
> working model and then focus on accuracy later.  Ideally I’d have  
> something that works in the next 2 weeks.
>
> Hopefully Panelite will have measured BTDF data in a few months that  
> we slot into the analysis.  If measured BTDF data doesn't become  
> available then we’ll focus on improving the accuracy of the  
> simulated BTDF.
>
> So I guess my first step is approximating a BTDF with Radiance.  I  
> was thinking I could a uniform sky above the panelite model as input  
> and a hemisphere of points below as sensors.  With rtcontrib I could  
> determine the light output in a direction for each input direction.   
> The input directions could be tregenza sky divisions (?).  The  
> output could be phi/lambda directions (?).  I imagine the key to a  
> decent BTDF is lots of samples for each output direction.  Maybe I  
> create a grid of 1000(00?) points in a plane just below the panelite  
> and use a script to create a hemisphere of sensor points centered at  
> each grid point.
>
> I know very little about BTDF’s and even less about creating them so  
> I could use any tips, tricks, guidance, watch its, how are you going  
> to account for?s and examples that anyone is willing to offer.
>
> Thanks,
> Andy
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