Rough/frosted glass

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DavidF
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Joined: Wed May 16, 2018 9:16 am

Rough/frosted glass

Post by DavidF » Wed May 16, 2018 9:58 am

Hi,

I think I have similar questions as forgeflow asked many years ago on the LuxRender forums (http://www.luxrender.net/forum/viewtopi ... =16&t=3252 ), i.e. why do objects using the rough glass shader appear darker when the roughness is increased?

Basically I am trying to create a material resembling frosted glass and I have done so by enabling the "Rough" option of the glass node. I expected that a higher roughness would generate a brighter surface (e.g. https://goo.gl/images/qEZvhD ), but instead the objects become dark. Any ideas why this happens or how I could create a better frosted glass material? I have attached the blend file I've been using for these tests.

Thanks in advance,
David

Roughness 0.02
Frosted_glass_roughness0.02.png
Roughness 0.2
Frosted_glass_roughness0.2.png
Attachments
Frosted_glass.blend
(638.93 KiB) Downloaded 5 times

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Dade
Developer
Posts: 1028
Joined: Mon Dec 04, 2017 8:36 pm

Re: Rough/frosted glass

Post by Dade » Wed May 16, 2018 10:23 am

DavidF wrote:
Wed May 16, 2018 9:58 am
I think I have similar questions as forgeflow asked many years ago on the LuxRender forums (http://www.luxrender.net/forum/viewtopi ... =16&t=3252 ), i.e. why do objects using the rough glass shader appear darker when the roughness is increased?
I have the feeling it may be due to an increase of internal reflections, have you tried to increase the max. path depths ? I will do a test.
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Dade
Developer
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Re: Rough/frosted glass

Post by Dade » Wed May 16, 2018 10:56 am

Ok, few notes about your scene:

- you are "1 1 1" values for the ground color, it is very unrealistic, you should use something more like "0.7 0.7 0.7" to physically plausible.

- you have a sky light source with gain "0.0 0.0 0.0" (outside a closed box). It is a noticeable waste rendering time.

- your max. depth setting are:

Code: Select all

path.pathdepth.total = 7
path.pathdepth.diffuse = 5
path.pathdepth.specular = 6
6 is definitively to low for glass rendering. You should at least double the values (including "path.pathdepth.total").

However I think there is the same problem I fixed a while ago for (non-rough) glass. Try to switch between roughglass and normal glass; with very little roughness, they should look the same however rough glass is a LOT darker. I will check the code.
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FiatLux
Posts: 20
Joined: Sat Apr 21, 2018 8:41 pm

Re: Rough/frosted glass

Post by FiatLux » Wed May 16, 2018 11:19 am

DavidF wrote:
Wed May 16, 2018 9:58 am
Any ideas why this happens?
It could be because the glass model.
This is the multi-scattering glass model that would fix the situation.

kintuX
Posts: 160
Joined: Wed Jan 10, 2018 2:37 am

Re: Rough/frosted glass

Post by kintuX » Thu May 17, 2018 2:25 pm

Frosted_Glass_DENOISED.png

Here i made Glass-Volume Homogeneous Volume with Multiscattering on & Upped the Glass Material Roughness to 0.2.
Also, made ground Matte 0.76 White Value, rendered with BiDir (5000samples), denoiser used & added a bit of tonne mapping for better contrast.
Glass-Volume.jpg
Glass-Material.jpg
Frosted_Glass-V.zip
(649.16 KiB) Downloaded 8 times

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