[Radiance-general] Color definition in Plastic material

[Germán Molina Larrain]

Hi Xiaoming,

mmm... I would say you are looking for a 60% reflective material (10%
specular, 50% diffuse).

In that case, I would choose a1, a2, a3 = 60% and the specularity would be
(C-rho_d)/C = 16,666%. (16.6666%*60% = 10%).

It seems that I have the same issue as you, though.... my calculation of
total reflectance is not correct when comparing to Lighting Materials
website.

Anyone actually know these things?

Kind regards,


2017-01-23 8:24 GMT-03:00 Xiaoming Yang <xiyang at fosterandpartners.com>:

> Hi Germán,
>
>
>
> Thank you very for your reply and suggestions. I am still not sure what
> values I should put in the material definition. According to the definition
> in:
>
> rho_d = p*C*(1-specularity)
>
>
>
> For a material with 50% of incoming light reflected diffusely and 10%
> specularly then
>
>
>
> C= 0.5/(1-0.1) = 0.555
>
>
>
> Shall I define the material as follow?
>
>
>
> Void plastic diffuse_50
>
> 0
>
> 0
>
> 5 0.555 0.555 0.555 0.1 0
>
>
>
> Regards,
>
> Xiaoming
>
>
>
> *From:* Germán Molina Larrain [mailto:germolinal at gmail.com]
> *Sent:* 20 January 2017 20:50
> *To:* Radiance general discussion <radiance-general at radiance-online.org>
> *Subject:* Re: [Radiance-general] Color definition in Plastic material
>
>
>
> Hello Xiaoming,
>
> If I understand the Materials documentation
> <http://radsite.lbl.gov/radiance/refer/materials.pdf> correctly, I would
> say that the Red, Green and Blue are total reflection. If specularity is
> non-zero, the diffuse reflection is reduced by this amount:
>
> rho_d = p*C*(1-specularity)
>
> At least, that would be my guess.
>
> Best!
>
>
>
> 2017-01-20 16:28 GMT-03:00 Xiaoming Yang <xiyang at fosterandpartners.com>:
>
> Hi,
>
>
>
> I have a rather basic question about color definition for plastic material
> and hope someone could help me.
>
>
>
> mod plastic id
>
> 0
>
> 0
>
> 5 red green blue spec rough
>
>
>
> *Does the red, green and blue define diffuse reflection or total
> reflection?*
>
>
>
> For example, if a material reflect 40% light diffusely and 10% specularly,
> is it correct to define this material as:
>
> Void plastic testMaterial
>
> 0
>
> 0
>
> 5 0.4 0.4 0.4 0.1 0
>
>
>
> I was checking with the spectrum data from SUTD
> http://www.lighting-materials.com/materials/648
>
>
>
> And it seems they are using the other approach which defines R G and B
> with total reflection and the material will be
>
> Void plastic testMaterial
>
> 0
>
> 0
>
> 5 0.5 0.5 0.5 0.1 0
>
>
>
> Xiaoming
>
>
>
> Foster + Partners Limited | Registered in England and Wales | CRN +
> 01644989
>
>
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