[Radiance-general] 5-phase method tutorial - section 6.1

[Leyla Sanati]

Thank you Greg. I really appreciate your help.

Leyla


On Fri, Aug 30, 2013 at 5:43 PM, Greg Ward <gregoryjward at gmail.com> wrote:

> Hi Leyla,
>
> I was thinking someone else might answer this one, as a lot of folks have
> worked on similar things, but here goes...
>
> Figuring out Radiance "trans" parameters is a classic challenge, and there
> are a few spreadsheets out there to make this a bit easier.  The basic
> reference is section 5.2.6 from "Rendering with Radiance," attached below
> for your convenience.  (Responders please delete attachment in your
> replies.)
>
> Plugging in your parameters of:
>
> Ts = .04
> Td = .67 - .04 = .63
> Rd = .18
> Rs = 0 (guessing no clear reflections)
>
> These yield:
>
> A7 = Ts/(Td+Ts) = .04/(.63+.04) = .0597
>
> A6 = (Td+Ts)/(Rd+Td+Ts) = (.63+.04)/(.18+.63+.04) = .7882
>
> A5 = 0 (adjust if you want to scatter your transmitted rays a bit)
>
> A4 = Rs = 0
>
> A1 = A2 = A3 = .18/((1-0)*(1-A6) = .18/(1-.7882) = .85 (assumes uncolored
> material)
>
> So, there's your material:
>
> void trans frosted_glass
> 0
> 0
> 7 0.85 0.85 0.85 0 0 0.7882 0.0597
>
> Regarding thickness, so long as the distance between slats is 16 cm or
> greater, you needn't worry about it.  If they are closer together, you may
> want to use the xform -a option to create your own array of slats.  It's
> actually pretty simple -- genblinds isn't doing that much for you with flat
> slats, anyway.
>
> Cheers,
> -Greg
>
> .
>
>
> *From: *Leyla Sanati <leylasanati at gmail.com>
>
> *Date: *August 29, 2013 10:00:45 PM PDT
>
> *
> *
>
> Dear list,
>
> Following example 1 in 5-phase method tutorial, I am trying to model
> venetian blinds with frosted glass as blind material. The properties of the
> glass are as follows:
>
> Visible Transmittance: 67%
> Reflectance: 18%
> Clarity (small-angle scattering): 4%
> Thickness: 8mm
>
> To generate accurate BSDF files, I thought I should model the blind slats
> as trans material, but I am struggling with translating above properties
> into trans material modifiers.
> I'd appreciate it if you helped me with writing the blind material script.
> Also, I am not sure where to include the glass thickness. genblinds does
> not seem to have an option for blind thickness.
> Does the glass thickness in this case affect the BSDF results?
>
> Thanks,
> Leyla
>
>
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