shadow color for glass issue

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daros
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Re: shadow color for glass issue

Post by daros »

Hi Kintux, unfortunately i cannot save blender files because i'm not a blender user.
I can deliver only luxcore and obj files. But luxcore has also 3D max users so i'm probably not the only one which has difficulties to deliver a blender file.
For this reason the scene i so basic. It fucus only on this specific prolem so the debug is easier. Despite it's non orthodox modelling it behaves exactly every other scene i have. The walls without thickness do not disturb since the environment is pure black. There are no polygon intersections enywhere in the scene.
Moreover the problem is so simple that everyone who has blender can reproduce it in 30 seconds, 1 box, a plane and one spot light. You should notice the same bahviour.

Here i completetely removed the box
Bidir on cpu
glass.JPG
The shadow you see behind the glass is correct but the one you see directly projected on to the red object is solid, which is wrong.

Isted if you do the same using PhotonGI you should get the other behiaviour i described in my previous post.
Luximage
Posts: 165
Joined: Sun Jan 14, 2018 8:01 pm

Re: shadow color for glass issue

Post by Luximage »

Here is the scene for blender(blender 3.1.2 /blendluxcore 2.61):
lightshadow.blend
(974.05 KiB) Downloaded 121 times
bidir
Lshadow Bidir.jpg
path
Lshadow path.jpg
kintuX
Posts: 809
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Re: shadow color for glass issue

Post by kintuX »

aha, bidir has too high PGI Glossines treshold set so no SDS paths
GlossTreshh.jpg
now, results match 8-) (disregarding brightness)

bidir+PGI.jpg
bidir

path+LT.jpg
path

more on...

BIDIRCPU can now use PhotonGI cache to render SDS paths
Luximage
Posts: 165
Joined: Sun Jan 14, 2018 8:01 pm

Re: shadow color for glass issue

Post by Luximage »

kintuX what version of blendluxcore are you using?
Making PGI glossiness threshold to zero doesn't change anything in version 2.61, also disabling PGI doesn't work either. Only in version 2.5 that Bidir doesn't work with PGI i get a correct matching result.
kintuX
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Re: shadow color for glass issue

Post by kintuX »

Luximage wrote: Sun May 01, 2022 1:45 pm kintuX what version of blendluxcore are you using?
I'm using 2.61alpha (homebuild) in Blender 3.2alpha on W10.
Luximage wrote: Sun May 01, 2022 1:45 pmMaking PGI glossiness threshold to zero doesn't change anything in version 2.61, also disabling PGI doesn't work either. Only in version 2.5 that Bidir doesn't work with PGI i get a correct matching result.
Oh, I didn't set it to zero, but 0.005 just lower than that of Red Disney Material - it's Blender merely showing 3 digits :roll:

Edited file attached.


PS.
Worth reading through some of PhotonGI cache thread.
Attachments
lightshadows.blend
(1.05 MiB) Downloaded 92 times
Luximage
Posts: 165
Joined: Sun Jan 14, 2018 8:01 pm

Re: shadow color for glass issue

Post by Luximage »

Hello kintuX thank you for the file, the difference in your file is not the glossiness threshold but enabling caustic cache and setting glass shadow color to black not to white.
Some renders from your file:
bidir bl.jpg
path bl.jpg
path wh.jpg
path wh no cau no LT.jpg

In blendluxcore 2.5 bidir doesn't support photon cache
bidir 2.5.jpg
kintuX
Posts: 809
Joined: Wed Jan 10, 2018 2:37 am

Re: shadow color for glass issue

Post by kintuX »

Luximage wrote: Sun May 01, 2022 9:46 pm Hello kintuX thank you for the file, the difference in your file is not the glossiness threshold but enabling caustic cache and setting glass shadow color to black not to white.
Indeed, and other changes... ;)
Luximage wrote: Sun May 01, 2022 9:46 pm In blendluxcore 2.5 bidir doesn't support photon cache
So no SDSD paths. Results match and I'm lost :lol: - :? What's wrong again?
Luximage
Posts: 165
Joined: Sun Jan 14, 2018 8:01 pm

Re: shadow color for glass issue

Post by Luximage »

Yes kintuX you made quite a few changes to that file :) .
In blendlucore 2.5 using bidir you just need to make the glass shadow color white, it matches the result of version 2.61 using path where the glass shadow is also white and only photon cache enabled(light tracing and caustic cache disabled). In those two examples the glass is not visible at all in the red capsule.
The other two examples that match are both in 2.61 version with glass shadow color kept black ,first one bidir with photon and caustic cache enabled and the second one path with photon, caustic cache, light tracing enabled. But in those two examples there is still some glass visible in the red capsule. See the image below.
bidir bl green note.jpg
daros
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Re: shadow color for glass issue

Post by daros »

Thank you all for the effort to understand the issue.
daros
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Re: shadow color for glass issue

Post by daros »

Hi, i created also this scene which isolates the problem with physical sky or HDRI under BIDIR.

No obstacles of any kind in the window
no obstacle.png


Obstacle with black shadow
black shadow.png



Obstacle with white shadow.
white shadow.png
I would expect the last scenes looking very similar to the first one, letting all direct sun and sky light in. Interesting is also the gradient artifact on the floor.

Please dade help us with this. It is truly important as you see because it strongly affects all interior scenes with natural light.

Attached the luxcore scenes and also the obj file
Attachments
backShadow.zip
(4.47 KiB) Downloaded 82 times
whiteShadow.zip
(4.48 KiB) Downloaded 78 times
noObstacle.zip
(3.65 KiB) Downloaded 80 times
obj scene.zip
(2.29 KiB) Downloaded 77 times
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