Radiance Trans mat translator from manufacturer product info

[zati89]

to generate a component which is giving you the Radiance Trans material properties based on manufacturers provided info, as this part is confusing. [proposed label] new devlopment, radiance @sariths

[zati89]

as far as I know the new EN 14501 the manufacturers measure light properties as follow:

• Solar transmission %
• Solar reflection %
• Solar absorption %
• Normal-hemispherical visible light transmission (total direct+diffuse transmission) %
• Normal-normal visible light transmission (specular transmission) %

as for example Serge Ferrari :https://sergeferrari.sharepoint.com/sites/WEBSITEPI/Brochures/BRO-Soltis-Horizon-86-EN.pdf?slrid=ddf19b9e-c0f1-7000-c0b0-14780cf898a1 or copaco https://www.copaco.be/UPLOADS/FILS/Copaco_Visi_Natte.pdf

So I think (but really just think :smile: ) that this should be our inputs. @sariths can you explain me what´s the difference between the solar transmission and the normal-hemispherical transmission ? This makes me a bit nervous cause I always thought that the Solar TR is the total direct+diffuse transmission

[sariths]

@zati89 The sharepoint link does not work (might be on your company LAN perhaps). Anyway, I think it is easier to follow a single standard laid out by a standards body like NFRC than devise a solution for each manufacturer. The only problem, as I mentioned on the forum, is that there doesn't seem to be an agreement (yet) on how to communicate this data. I was told that onne of the initiatives of the IEA Task 50 seems to be heading in that direction. Back to the original topic, the excel file that I gave you appears to be compatible with Mechoshade and Hunter Douglas (both US based firms).

[zati89]

hi @sariths , that´s the sharepoint of SergeFerrari the biggest screen manufacturer, at least for the European ans Asian market.

https://www.sergeferrari.com/products/soltis-range/soltis-perform-92 donwload the Brochure please. -communication of the data, that I feel also bad. But do far we have this EN 14501 according to which (at least the European) manufacturers measure and share the properties of screens (see screenshot attached and the link to the brochure). How is Mecoshade sharing their data? or what they share ?

[sariths]

Hi @zati89 , just a quick (non) update... I had been piled in with office stuff the last few days.. I will restart this thread with some constructive comments sometime later this week.

[zati89]

Hi @sariths , no worries I was in bed for the last week, didn´t even turn on a machine. Yesterday I had a talk with my colleagues who knows less about materials etc. which I assume people out there are also on the same level, and they would like to have the same input as some manufacturer..... doesn´t matter if SergeFerrari or Mecoshade.... But what I´m afraid of is that the material properties of a screen shade (fabric) and a Trans material are different. For example that the transmission in a Trans material doesn´t change under diff. angle, although with screens(fabrics) you have some cut offs. https://www.dropbox.com/s/crhi2hfawfwld87/Fabrics-Wienold.pdf?dl=0

[sariths]

For example that the transmission in a Trans material doesn´t change under diff. angle, although with screens(fabrics) you have some cut offs.

Yup, you are talking about anisotropic shading devices, which are (arguably) handled better through t4 BSDFs.

[zati89]

when we had a talk with Jan, he told us that BSDF can´t handle it, that´s why he did the way he did with BRTD and glass in front, as the paper attached says

[sariths]

when we had a talk with Jan, he told us that BSDF can´t handle it,

@zati89 I am wondering if that limitation of BSDFs was specific to what can be measured and transmitted currently. All the empirical data is only transmitted through Klems-basis in the LBNL databases, which essentially comes to down 145 in/out directions. The t5 tensor tree is supposed to be handling this through a higher order. So, standard shades, which are not directional sensitive are handled through t4 and all the other types of fenestrations that are direction-sensitive are handled through t5 (or so I have been told). Anyway, I am glad that we are having this discussion, because this is something that I can ask the folks at LBNL when I revise the Radiance tutorial with corrections and additions.

[zati89]

@sariths , exactly that wanted to ask you, If you can ask Greg, If we can simply make the geometry of the fabric in Rhino (cause there we can do small openings (1mm or so),)and also give it a depth of 1-2mm) and generate a t5 BSDF, so we have the cut off angles handled etc. But I think for quick and dirty simulations we can use the trans material, but not for glare I think.

[zati89]

Hey @sariths , I just realized that a loooong time ago on the Radiance forum a similar question came up, and Lars answered it pretty nicely : https://discourse.radiance-online.org/t/trans-parameters-for-translucent-fabric/4388 , and so we can mimic the widget then http://gaia.lbl.gov/people/andy/public/transwidget/ what do you say ? (obviously assuming the specularity being 0 and the roughness also 0 for the beginning- as mentioned in Larses answer), or do we need something more exact ?

[sariths]

Hi @zati89,

Can we get started with the math part of it first? As in creating the workflow for a couple of usecases. I know that Mostapha is planning to split the [+] libraries into separate sections. So, it would be wise to wait for that to happen before we try to push the functionality into the code.

Regards,

Sarith

On 3/5/2019 3:11 PM, zati89 wrote:

Hey @sariths https://github.com/sariths , I just realized that a loooong time ago on the Radiance forum a similar question came up, and Lars answered it pretty nicely : https://discourse.radiance-online.org/t/trans-parameters-for-translucent-fabric/4388 , and so we can mimic the widget then http://gaia.lbl.gov/people/andy/public/transwidget/ what do you say ? (obviously assuming the specularity being 0 and the roughness also 0 for the beginning- as mentioned in Larses answer), or do we need something more exact ?

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[zati89]

hey @sariths ,

So If we use the widget of Andy Mcneil (http://gaia.lbl.gov/people/andy/public/transwidget/), then we should use the following logic:

mod trans name   | 0   | 0   | 7 A1 A2 A3 A4 A5 A6 A7   |     | A7 = Ts / (Td+Ts)   | A6 = (Td+Ts) / (Rd+Td+Ts)   | A5 = Roughness   | A4 = Rs   | A3 = ( (1-Rs) (1-A6) )   | A2 = ( (1-Rs) (1-A6) )   | A1 = ( (1-Rs) * (1-A6) )

_Td=0.03 (normal-hemispherical minus normal-normal) Ts=0.14 (normal-normal) Rd=0.61 (guessed from given solar reflection) Rs=0.00 (perfectly diffuse, so no specularity) Roughness=0 (we simply have no information based on your data)

Entering this into the trans widget leads to

Td=0.03 Ts=0.14 Rd=0.61 Rs=0

void trans translucentfabric 0 0 7 0.78 0.78 0.78 0 0 0.218 0.824

interestingly there is no R,G and B diffuse reflectance to fill into the widget

[sariths]

@zati89 So, the full code implemented there is inside this javascript file: http://gaia.lbl.gov/people/andy/public/transwidget/main.js . This should be easy to figure out. Let me see if I can steal some time this weekend to write a Python translation for this.

[zati89]

@sariths cool :+1: :)

[mostaphaRoudsari]

I might be wrong but this is already implemented in honeybee Trans material. See here:

https://github.com/ladybug-tools/honeybee/blob/3cb8af4faafd6f4bfbb05adb85641396a5133271/honeybee/radiance/material/trans.py#L69-L135

or is it something different?

[sariths]

@mostaphaRoudsari I remember there being some missing aspect to this implementation. But I might be mistaken, I need to check the results generated by this method to that generated by the spreadsheet. You can keep the issue open for now.

[mostaphaRoudsari]

@sariths sounds good! This method is based on the workshop presentation.