Reducing roughness by value

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lighting_freak
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Joined: Thu Jan 18, 2018 6:02 pm

Reducing roughness by value

Post by lighting_freak » Thu Jun 25, 2020 9:24 am

Hello all,

what happens if I reduce the roughness value (limit with direct entry is 0,001) with the help of an value node?
roughness.jpg
Is it possible to reach lower roughness values with this trick?
Thank you.

BR
OS - Windows 7 X64
CPU - Intel CORE i7
GPU1 - Variants of notebook card from nVidia
GPU2 - Variants of notebook onboard card from Intel
Lux - Latest possible relaease

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Dade
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Re: Reducing roughness by value

Post by Dade » Thu Jun 25, 2020 9:53 am

lighting_freak wrote:
Thu Jun 25, 2020 9:24 am
Is it possible to reach lower roughness values with this trick?
It is limited by the code to 1e-9: https://github.com/LuxCoreRender/LuxCor ... y2.cpp#L76

You can export the scene in text format to check how your node setup is exported.
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Fox
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Re: Reducing roughness by value

Post by Fox » Thu Jun 25, 2020 9:58 am

Yes, i use all the time 0.00000001 for glass with BiDirVM + Sun or Sun on HDRmap.
The BiDirVM renders sun black with clear glass.

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B.Y.O.B.
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Re: Reducing roughness by value

Post by B.Y.O.B. » Thu Jun 25, 2020 10:52 am

Dade wrote:
Thu Jun 25, 2020 9:53 am
It is limited by the code to 1e-9
Should I use 1e-9 in the Blender addon as well?

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Dade
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Re: Reducing roughness by value

Post by Dade » Thu Jun 25, 2020 10:58 am

B.Y.O.B. wrote:
Thu Jun 25, 2020 10:52 am
Dade wrote:
Thu Jun 25, 2020 9:53 am
It is limited by the code to 1e-9
Should I use 1e-9 in the Blender addon as well?
I don't think so, 1e-9 is a limit coming from old Lux and it is too small: if you check few line after, there is a square of the number (and than a division too) and it is very likely to end as a 0 with FP32. Using so small numbers is asking for troubles.
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Fox
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Re: Reducing roughness by value

Post by Fox » Thu Jun 25, 2020 11:56 am

1e-8 is lowest that has worked for me.

Are there any other FP32 limitations for volume absorption in small scale rendering, like jewelry?

Like say a gemstone 2mm in size, sometimes you change transmission 2.5 times lower, but it goes from full transparent to pure black?

lighting_freak
Posts: 194
Joined: Thu Jan 18, 2018 6:02 pm

Re: Reducing roughness by value

Post by lighting_freak » Tue Jun 30, 2020 4:35 am

Hi,

Thanks for your help.
This one is a good question too.
I had some troubles in the past as well:
Fox wrote:
Thu Jun 25, 2020 11:56 am
Are there any other FP32 limitations for volume absorption in small scale rendering, like jewelry?
BR
OS - Windows 7 X64
CPU - Intel CORE i7
GPU1 - Variants of notebook card from nVidia
GPU2 - Variants of notebook onboard card from Intel
Lux - Latest possible relaease

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