Weird behavior

[nicola_barbano]

Hi!
First of all I'm trying to figure out if they are my workstations (two) broken or 3dsMax (2022) or VRay (release 2.1). I have this really weird behavior in my scene and it has never happened before.

I've created from zero this iper basic TEST scene...just two cubes (one red, one white), VRayPlane, VRay Sun/Sky and a primitive plane as roof. Nothing else, very iper simple.

The problem:
The cubes under the plane/roof produce light on top...they stop only if I turn off the VRay Sun or if I create another plane/roof on top of the existing one. So two planes.
I tried everything (also re-installed VRay), even closing the plane like a room. But the cubes keep producing light. I'm going crazy.
Do you know what it could be?
Please see the jpg.

Thank you!
Nico

[Alex_M]

Hi. Looks like light leak problem due to having objects with no thickness and very bright light sources shining on them. Try adding a shell modifier to the plane to add some thickness to the walls and ceilings. Also, check if the objects are properly scaled and if they are close to the center of the scene. Putting objects and camera very far away from the scene center can cause problems too.

[nicola_barbano]

Hi,
Yes I thought the same but it's a weird behavior.
If I add a shell modifier it deseappers, you are right, but apparently only if I keep the shell higher than 7cm!...Please see my JPG. At 8cm it deseappers, but 7cm it come back. So weird.
Yes the scene is scaled correctly (I use mt) and in zero coordinates, of course.
I wondering if it happens only to me...

[Alex_M]

It's going to be hard to figure out without checking the scene. Would it be possible to share it here?

[Buck]

possibly the shadow bias setting on the light needs to be adjusted to be lower?

[nicola_barbano]

It's going to be hard to figure out without checking the scene. Would it be possible to share it here?

HI,
Yes here the TEST scene...as I said it's iper basic just a cubes and planes and all settings are default.

[nicola_barbano]

possibly the shadow bias setting on the light needs to be adjusted to be lower?

Hi,
Yes!...If I put lower like 0.1 (default is 0.2) it disappear. Thank you for the advise!
I find that in any case it's a weird behavior, when by default using VRaySun they should be ok for this. I mean that it's not a specific or complex scene where maybe you need to tweak the spec of the Sun. It's just a cube with above a plane, that's it.
In years I've never seen this problem!
Thank you!

[fixeighted]

It's been mentioned that that bias parameter will disappear at some point, as the default doesn't make sense any more and should be set to 0 to avoid any weird stuff occurring

[nicola_barbano]

It's been mentioned that that bias parameter will disappear at some point, as the default doesn't make sense any more and should be set to 0 to avoid any weird stuff occurring

Hi,
Oh this is a good news! It's a bit silly that in 2024 I still need to tweak (by default) the Sun for this.
I didn't know about that...Thank you for letting me know!

[kosso_olli]

It's been mentioned that that bias parameter will disappear at some point, as the default doesn't make sense any more and should be set to 0 to avoid any weird stuff occurring

Well, it could have disappeared around 10 years ago... It is time.

[nicola_barbano]

Well, it could have disappeared around 10 years ago... It is time.

Eheheheh!I think so!

[nicola_barbano]

It's going to be hard to figure out without checking the scene. Would it be possible to share it here?

Hi!Out of curiosity, did you check my test scene?

[Alex_M]

Hi!Out of curiosity, did you check my test scene?

Yes, sorry for the late reply. I check the scene and indeed, as others already mentioned, the problem was that "Shadow bias" was too high. Just lower it until it disappears. You don't normally need to do this when the scene units are centimeters or inches, but appears that with meters as scene units the default value is too high.

[nicola_barbano]

Absolutely no "sorry"...I was just asking!
Yes, I'm using meter for work.

Thank you all for helping me and resolve it!
Nico