[Radiance-general] glaze script limitation

[Greg Ward]

Hi Jack,

Would this really solve the problem?  Logically, it makes sense to allow the "clear" glass to be any uncoated glazing, but the way it's currently used in the script, it only serves as a reference point.  In fact, the first entry isn't used unless both surfaces of a pane are given as "clear".  The trouble, as I said, is that any coating on a different sort of glazing requires measurements of that _combination_.  I don't know how to compute the combined effect in the original example, below:

> I would like to model a double glazing system like the following:
>  
> first pane
> surface 1: Crystal gray (Optics database number:  3056)
> surface 2: Crystal gray with a SunGuard Ag 43 coating (Optics: 3156)

For this, we need to employ Optics or Window 6 or extract their simulation engine.  What I was suggesting instead is that we permit the user to enter the transmittance and reflectances from Optics for the desired pane, substituting this for the database values we would normally use.  It sort of breaks the current interaction model for the user interface, but it would allow a little more flexibility as a benefit.

Does this make sense?

-Greg

P.S.  We can take this conversation offline or move it to dev if you like -- I'm not sure if it's of general interest to others on the list.

---------------------------
> From: Jack de Valpine <jedev at visarc.com>
> Date: December 16, 2010 8:17:52 AM PST
> 
> Hi Greg and Francois,
> 
> Greg, would it work to just make sure that one surface of any layer is "uncoated" (eg where Rf ==  Rb perhaps withing some small error range) rather than "clear"? Thus allowing for different clear/uncoated glass to be used as surfaces on different layers?
> 
> -Jack
> 
> On 12/16/2010 11:01 AM, Gregory J. Ward wrote:
>> Hi François,
>> 
>> I gave this a little more thought after letting the problem sink in, and I don't see now why you couldn't do as you suggested and add a glazing to the database that contains your desired properties.  You would have to "lie" and tell the script that one of your two surfaces was glass, then pick your new entry as the other surface, but the result should be accurate.  The glaze script actually ends up using the specified non-glass surface parameters in its calculations -- the glass surface is just there as a reference.
>> 
>> The other thing I said is still true -- namely, that we can't practically offer all the possible pairings of surface coatings because they would balloon the database, but if you don't mind adding your own, I don't see why you can't do it that way with the current script.  We probably should offer an option to enter custom transmittances and front&  back reflectance values for advanced users, and this wouldn't be too difficult to add.  I wonder if we could take pasted output from Optics, directly?  I don't know if they have a format that gives us the naked data, but I suppose we could extract it from the Optics output for Radiance.
>> 
>> Best,
>> -Greg