Page 1 of 1

Reducing roughness by value

Posted: Thu Jun 25, 2020 9:24 am
by lighting_freak
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

Re: Reducing roughness by value

Posted: Thu Jun 25, 2020 9:53 am
by Dade
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.

Re: Reducing roughness by value

Posted: Thu Jun 25, 2020 9:58 am
by Fox
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.

Re: Reducing roughness by value

Posted: Thu Jun 25, 2020 10:52 am
by B.Y.O.B.
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?

Re: Reducing roughness by value

Posted: Thu Jun 25, 2020 10:58 am
by Dade
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.

Re: Reducing roughness by value

Posted: Thu Jun 25, 2020 11:56 am
by Fox
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?

Re: Reducing roughness by value

Posted: Tue Jun 30, 2020 4:35 am
by lighting_freak
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