[Radiance-general] Color definition in Plastic material

[Xiaoming Yang]

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<mailto: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

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