How to represent a glazed surface in radiance

Dear community,
A quick question. Which material for interior cladding would be the best to represent a material with a glazed surface?
Any input is much appreciated :slight_smile:

/Per

Hi Per,

I would guess a plastic with a high specularity value would behave the way you want...

路路路

On 11/19/15, 1:39 AM, "Per Haugaard" <perhaugaard@yahoo.dk<mailto:perhaugaard@yahoo.dk>> wrote:

Dear community,

A quick question. Which material for interior cladding would be the best to represent a material with a glazed surface?

Any input is much appreciated :slight_smile:

/Per

Unless the glaze is metallic, in which case using "metal" would be better to specify the specular color. Even with a glazed surface, a non-metallic material shouldn't have a specularity above about 0.06 to be realistic.

-Greg

路路路

From: "Guglielmetti, Robert" <Robert.Guglielmetti@nrel.gov>
Subject: Re: [Radiance-general] How to represent a glazed surface in radiance
Date: November 19, 2015 7:00:16 AM PST

Hi Per,

I would guess a plastic with a high specularity value would behave the way you want...

On 11/19/15, 1:39 AM, "Per Haugaard" <perhaugaard@yahoo.dk<mailto:perhaugaard@yahoo.dk>> wrote:

Dear community,

A quick question. Which material for interior cladding would be the best to represent a material with a glazed surface?

Any input is much appreciated :slight_smile:

/Per

Dear Greg an Robert,
Thank you very much for your quick and usefull answer.Have a nice weekend.

Best regards
Per Haugaard

Unless the glaze is metallic, in which case using "metal" would be better to specify the specular color. Even with a glazed surface, a non-metallic material shouldn't have a specularity above about 0.06 to be realistic.

-Greg

路路路

Den 17:50 torsdag den 19. november 2015 skrev Greg Ward <gregoryjward@gmail.com>:

From: "Guglielmetti, Robert" <Robert.Guglielmetti@nrel.gov>
Subject: Re: [Radiance-general] How to represent a glazed surface in radiance
Date: November 19, 2015 7:00:16 AM PST

Hi Per,

I would guess a plastic with a high specularity value would behave the way you want...

On 11/19/15, 1:39 AM, "Per Haugaard" <perhaugaard@yahoo.dk<mailto:perhaugaard@yahoo.dk>> wrote:

Dear community,

A quick question. Which material for interior cladding would be the best to represent a material with a glazed surface?

Any input is much appreciated :slight_smile:

/Per

Per,
For a little extra clarity, when you say "glazed" are you talking about glazed surface such as glazed terra cotta or similar, such as the way you would use the term in reference to pottery? Or are you referring to "glazed" such as being framed and covered in glass, like an opaque back-painted glass wall?

Greg,
If it were a glass with opaque paint on the back side, would you still say the 0.06 specularity would represent the mirror-like reflections from the smooth glass surface?

If it were glass with any type of reflective treatment it could obviously have higher specularity. What if the front face of the glass is 0.06 specularity but the wall behind the glass could also be high gloss paint and add another 0.06?

I'm probably getting beyond the level of what's possible to estimate without talking about specific materials. But maybe there's a little extra of the theory behind it to understand.

路路路

-----Original Message-----
From: Greg Ward [mailto:gregoryjward@gmail.com]

Unless the glaze is metallic, in which case using "metal" would be better to specify the specular color. Even with a glazed surface, a non-metallic material shouldn't have a specularity above about 0.06 to be realistic.

-Greg
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A regular piece of glass has about 4% front-surface reflection, so glazing a material (where you create a single dielectric interface) typically matches this 4%. If the outer surface is smooth, which is the general reason you would glaze something, then you get nice highlights due to low scattering rather than the amount of light that is reflected. The amount of light reflected also increases towards grazing due to Fresnel's law, which is modeled correctly by "metal" and "plastic" when the roughness is zero.

To get two dielectric surfaces, which would add to 8% or so as you suggest, you would need the coating to not quite meld with the underlayer. This is what plastic wrap looks like on a surface, and is not generally what people go for when glazing ceramics, etc.

Cheers,
-Greg

路路路

From: Christopher Rush <Christopher.Rush@arup.com>
Subject: Re: [Radiance-general] How to represent a glazed surface in radiance
Date: November 20, 2015 9:47:16 AM PST

Per,
For a little extra clarity, when you say "glazed" are you talking about glazed surface such as glazed terra cotta or similar, such as the way you would use the term in reference to pottery? Or are you referring to "glazed" such as being framed and covered in glass, like an opaque back-painted glass wall?

Greg,
If it were a glass with opaque paint on the back side, would you still say the 0.06 specularity would represent the mirror-like reflections from the smooth glass surface?

If it were glass with any type of reflective treatment it could obviously have higher specularity. What if the front face of the glass is 0.06 specularity but the wall behind the glass could also be high gloss paint and add another 0.06?

I'm probably getting beyond the level of what's possible to estimate without talking about specific materials. But maybe there's a little extra of the theory behind it to understand.