Interference pattern using spot light

don’t know if it really is a bug or a feature. But, if I use a spot light (3 light setup) I see an interference pattern appearing on the surface. Switching it to point light let it disappear.

First picture is with spot light, on the second I switched it to point light.
I played through all post processing settings, but only switching spot light to point light helped.

Btw: Android, Samsung Galaxy tab S7

Have you tried to switch of shadow on spot light?
I guess the issue is there.

Here, both time shadow is on. But in the picture with artefacts, I placed an object between light & leaf dropping a shadow.

Same issue with directional light.

Could you send me the glb file, with everything set up so that the bug appears when opening the file?

Thanks, I sent you a mail.

Ah thanks!

I wanted to reply to @knacki as the file looked simpler.

As I suspect I don’t replicate the bug on my iPad Air4, probably a GPU things. It’s definitely caused by shadows though.
I can reproduce the bug on my galaxy Tab S7 though, maybe I’ll try to find a workaround.

The annoying thing is it’s sometimes not possible to detect on which device the bug appears (if it was only Android it would be simpler but I think it can happen on some iOS device as well).

I suspect it to be related with the amount or position of objects in the scene, although some are not visible. If I delete all the non-visible objects, the interference disappears, too.

I was playing around with the non-visible objects. It seems their position slightly affects the interference pattern.
So: maybe it has to do with the amount of objects or the way the device handles them? Or even simpler: spot lights ignores the visibility toggle of objects, if the amount the device can handle is surpassed?

Btw: by my invisible objects you might realize, I’m really new to all the art stuff. However, it reminds me to an effect I simulated during my studies of physics, simulating interfering light paths, including back scattering. So my entrance sentence: Is this a bug or a feature?

Update: if I delete the non-visible object: 006-0-6.001 in my file the interference is gone. So… something related to this object seems to induce this interference. Maybe @knacki has also an invisible object in his scene?

I tested around with my issue, which seems to be maybe a bit different.
Take a light source (directional is easiest) an object to drop a shadow on your sculpt and the sculpt itself.

If the shadow dropping object is close by, you won’t see anything.
But if you place the shadow dropping object far away but still casting a shadow onto the sculpt, the problem occurs.

Maybe just a simple matter of shadow map resolution in my case?

@knacki Could you send me your file?

I replicate the issue with spot light on @Aszrael model but not with directional light.

Directional are different enough from spot light that it might be another issue, so I’d like to check that out.

It’s a precision issue, caused by the near/far ratio that is too high in the light camera.

Usually it’s simple to fix but the annoying thing is that gpu are more annoying that cpu as things are not consistent and I don’t want to reduce the shadow quality just because of a few devices (not really the case here as it impacts both a few Android devices and a few iOS one).

So 1.58 is out and the shadow issue should be mostly fixed @Aszrael.

As for your model @knacki I didn’t spot any issues on my device.
The 2 objects are small relatively to the entire scene, so the shadow will definitely be very blur due to the low resolution shadow map in Nomad. But I don’t see the same patterns as in your screen.

1 Like

Thanks, great to see a developer putting so much effort in his program!