Shadow Terminator problem

Discussion related to the Engine functionality, implementations and API.
User avatar
Dade
Developer
Posts: 3362
Joined: Mon Dec 04, 2017 8:36 pm
Location: Italy

Re: Shadow Terminator problem

Post by Dade » Sat Aug 10, 2019 2:32 pm

Racleborg wrote:
Fri Aug 09, 2019 5:21 pm
I am not sure if this is relevant to the currently discussed Bump issue, but I don't appear to be getting any Bump effect be with the Checkerboard Texture like it does with other textures such as Distorted Noise?
This should be normal: the bump is proportional to the difference of 2 adjacent pixels, if the pixels have the same color (like inside a check), there is no difference and the normal is unmodified. So it is modified only on the sharp edge between 2 checks.
Support LuxCoreRender project with salts and bounties

User avatar
Dade
Developer
Posts: 3362
Joined: Mon Dec 04, 2017 8:36 pm
Location: Italy

Re: Shadow Terminator problem

Post by Dade » Sat Aug 10, 2019 2:45 pm

provisory wrote:
Sat Aug 10, 2019 8:09 am
I think it is related, that strong bump mapping flips normals:
Normals aren't really flipped, I checked the values, they just become tangent to the plane so the point emits light 90 degree over and 90 degree under the plane. Stronger is the bump map and more points will have tangent normals and more light will be emitted under the plane.

I would consider this expected (or just a different type of problem).
Support LuxCoreRender project with salts and bounties

User avatar
Dade
Developer
Posts: 3362
Joined: Mon Dec 04, 2017 8:36 pm
Location: Italy

Re: Shadow Terminator problem

Post by Dade » Sat Aug 10, 2019 3:38 pm

I decoupled the UV scale and strength, so changing the UV scale doesn't affect bump mapping strength anymore.
Support LuxCoreRender project with salts and bounties

User avatar
FarbigeWelt
Donor
Posts: 882
Joined: Sun Jul 01, 2018 12:07 pm
Location: Switzerland
Contact:

Re: Shadow Terminator problem

Post by FarbigeWelt » Sat Aug 10, 2019 3:54 pm

Dade wrote:
Sat Aug 10, 2019 3:38 pm
I decoupled the UV scale and strength, so changing the UV scale doesn't affect bump mapping strength anymore.
Thank you this is much more intuitive because uv map is 2D and its scaling is not expected to change z even if uv map is used as bump map (with influence on z looking).
Light and Word designing Creator - www.farbigewelt.ch - aka quantenkristall || #luxcorerender
160.8 | 42.8 (10.7) Gfp | Windows 10 Pro, intel i7 4770K@3.5, 32 GB
2 AMD Radeon RX 5700 XT, 8 GB || Gfp = SFFT Gflops

User avatar
lacilaci
Donor
Posts: 1642
Joined: Fri May 04, 2018 5:16 am

Re: Shadow Terminator problem

Post by lacilaci » Sat Aug 10, 2019 4:17 pm

Dade wrote:
Sat Aug 10, 2019 3:38 pm
I decoupled the UV scale and strength, so changing the UV scale doesn't affect bump mapping strength anymore.
good news :)

I tried to lookup if other renderers didn't have to deal with this type of issue...

And for most it's related to glossy reflection under extreme circumstances, diffuse component never turns black in any other renderer.

Anyways, here's best I found, but I'm not sure if it's of any use for luxcore:
https://blogs.unity3d.com/2017/10/02/mi ... h-tracing/

kintuX
Posts: 477
Joined: Wed Jan 10, 2018 2:37 am

Re: Shadow Terminator problem

Post by kintuX » Sat Aug 10, 2019 4:54 pm

Dade wrote:
Sat Aug 10, 2019 3:38 pm
I decoupled the UV scale and strength, so changing the UV scale doesn't affect bump mapping strength anymore.
Terminator tamed :D Looks nice.

But is it known that Caustics & Bump don't work well together?

Also, something with OCL is causing Lux to freeze when stopping the render. Within Blender or UI only. And I don't get any error.
IIRC, similar bug appeared before.
Here (scene for LuxcoreUI) it happens when after I Pause it, change the Halt time and press Apply. Freeze! To kill. :?
FreezingScene.7z
(6.73 MiB) Downloaded 17 times
TerminatorBumpsLuxCore2.2b3_CPU.jpg

User avatar
Dade
Developer
Posts: 3362
Joined: Mon Dec 04, 2017 8:36 pm
Location: Italy

Re: Shadow Terminator problem

Post by Dade » Sat Aug 10, 2019 6:12 pm

lacilaci wrote:
Sat Aug 10, 2019 4:17 pm
Anyways, here's best I found, but I'm not sure if it's of any use for luxcore:
https://blogs.unity3d.com/2017/10/02/mi ... h-tracing/
I have the code for this is: https://github.com/LuxCoreRender/LuxCor ... f.cpp#L149 (http://www.aconty.com/pdf/bump-terminat ... ia2019.pdf)

This year new SIGGRAPH paper is supposed to be an improvement over that one.
Support LuxCoreRender project with salts and bounties

User avatar
Dade
Developer
Posts: 3362
Joined: Mon Dec 04, 2017 8:36 pm
Location: Italy

Re: Shadow Terminator problem

Post by Dade » Sat Aug 10, 2019 6:14 pm

kintuX wrote:
Sat Aug 10, 2019 4:54 pm
Dade wrote:
Sat Aug 10, 2019 3:38 pm
I decoupled the UV scale and strength, so changing the UV scale doesn't affect bump mapping strength anymore.
Terminator tamed :D Looks nice.

But is it known that Caustics & Bump don't work well together?
The "taming" is currently limited to DIFFUSE and GLOSSY materials: https://github.com/LuxCoreRender/LuxCor ... f.cpp#L243

I haven't yet tried how it works with SPECULAR materials.
Support LuxCoreRender project with salts and bounties

User avatar
Dade
Developer
Posts: 3362
Joined: Mon Dec 04, 2017 8:36 pm
Location: Italy

Re: Shadow Terminator problem

Post by Dade » Sat Aug 10, 2019 6:15 pm

kintuX wrote:
Sat Aug 10, 2019 4:54 pm
Here (scene for LuxcoreUI) it happens when after I Pause it, change the Halt time and press Apply. Freeze! To kill. :?
I will try to reproduce the problem.
Support LuxCoreRender project with salts and bounties

User avatar
lacilaci
Donor
Posts: 1642
Joined: Fri May 04, 2018 5:16 am

Re: Shadow Terminator problem

Post by lacilaci » Sat Aug 10, 2019 6:26 pm

So do we know why are these dark patches and how to fix that?

I wonder how is it that other renderers don't suffer from this. Maybe some dirty tricks to limit normals or bump strenght?

Post Reply