Hi!

I have to set up three custom material for a project I need to work on:

- Glass: low-e with 77% translucency

- Membrane. This is kind of textile material that is also use for sailing. Translucency of 11.4% and a solar reflectance of 74.5%.White color

- The last one is for the generic interior and has 65% reflectance and white color

I tried to customize materials before, but with lots of problems, and in the end I used the default one.

This time I have to set the precise one.

Any help would be very much appreciate.

Thanks,

Federico

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Hello Federico,

We do have a guide page on customizing materials, but it is rather sparse. The first and last materials are easy.

Clear Glass Materials

If you have a glass with a transmittance of X, then its transmissivity (used in Radiance) is approximately X * 1.09. Your material is then as below. Note that transmittance and transmissivity are between 0 and 1. 50% transmittance --> 0.5 * 1.09 = 0.545 transmissivity.

void glass NameOfMaterial

0

0

3 Transmissivity Transmissivity Transmissivity

Generic 'Plastic' Materials

If you know reflectance value, it is easy to turn into a plastic type material. Again, all values are between 0 and 1.

void plastic NameOfMaterial

0

0

5 R-Reflectance G-Reflectance B-Reflectance Specularity Roughness

R, G and B reflectance are equal for white materials. Specularity and roughness can be left as 0.

Your membrane material is more difficult. Is 100% of the light transmitted diffuse? Or is there some vision component as well?

Best,

Alstan

Hi Alstan,

Thanks for the reply.

I have some question regarding what you replied:

- Regarding the Glass:

As I understand all the transmittance has to be converted in transmissivity, right?

In my case you set the transmittance of my glass at 0.5. Is there a reason for this?

They gave me a translucency of 77%.

- Generic interior 65% of reflectance

could be something like this?:

void plastic Generic Interior 65

0

0

5 0.65 0.65 0.65 0 0

Thanks again for the help

Dear Federico,

The 0.5 value for the glass was just as an example. You would do the calculation using the 0.77 value provided by the manufacturer.

Your plastic material is mostly correct, but you need to remove the extra spaces in order to work with the software (space is a field separation character). The material name should be Generic_Interior_65

Best,

Alstan

Hi Alstan,

I have been working on the third material.

Could be ok this one?

void trans Trans_Material
0
0
7 0.606 0.606 0.606 0.01 0 0.833 0.2

Thanks again,

Federico

Hello Federico,

The visual properties of your trans definition are as follows,

Specular reflectance            1.0%
Diffuse reflectance            10.0%
Diffuse transmission            40.0%
Specular transmission            10.0%

I am attaching an Excel document I use to track the derived meaning of trans definitions, which you might find useful.

Best,

Alstan

Specular reflectance 1.0%
Diffuse reflectance 10.0%
Diffuse transmission 40.0%
Specular transmission 10.0%
Attachments:

Hi Alstan,

Thanks again for your help. The file you created it is very easy to use.

The material part is the one that for me it is the most time consuming.

It would be fantastic if diva would have a bigger pre-set library with the most common construction materials, instead of creating for each project new ones.

Thanks for your work.

Best,

Federico

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