LuxCoreRender Forums

daros wrote: ↑Mon Oct 11, 2021 7:12 am Hi dade, attached is the luxcore scene.

The scene is just all black

Have you tried it ?

Slow on my 4 cores PC, but i get this...
You don't get that?

Are you using v2.5 ?!?

2.6 Alpha 0. Only on my machine i use the 2.5, sorry.
Anyway under 2.6 Alpha 0 we get this

Hi dade, i upload you the scene again, who knows... We are using the Luxcore you uploaded yesterday.

It render as black here, if I increase the exposure by 10 times, I start to see something.

Anyway, I loaded the .ply inside Blender to make some sense of it. I'm guessing your problem is: direct light goes trough "shadow transparency" while indirect light doesn't. And your test scene has no direct light at all.

To test this, you point a light source to the glass box (i.e. direct light). Than just flip the light source by 180 degree (i.e. it is pointed to a wall, so the glass box is lighted only by indirect light). Is that the problem ?

No, it's not a simple direct-indirect light problem.

I did some tests regarding this.

In this scene all materials are white matte.

Direct light
indirect light (min 8 bounces before reaching glass)
As you see everything is correct.

The problem shows up as soon as the light is bounced by a slightly glossy material.
The only difference between this scene and the previous ones is that the wall material, which is reverberating the light to our cage, is slightly reflective/glossy.
The luxcore scene of the last picture is exactly the one i sent you today. If you replace the material assigned to the "space" layer with a white matte you get again the correct result.

Thanks a lot for your help dade.

I think it's a problem of caustics. Caustics are not let through a glass with white shadow output.

Hi dade, here are additional tests and comparisons with pure caustics lighting.

Luxcore white shadows interestingly luxcore is trying to build caustics behind glass

Maxwell white shadows (hidden from global illumination) interestingly maxwell il able to add a decent amount of light behind the glass.
But this light has not much to do with the original beam you notice if we hide the glass, see last picture.

Luxcore normal shadows interestingly this rendering is almost identical to the white shadows one, just a bit noisier.

Maxwell normal shadows It seems that the physically correct Maxwell do not even tries to let the caustics through

Luxcore and Maxwell no glass, same result. The amount of light lost because bad caustichs calculations can be relevant.

Hi dade, can we help somehow to solves this problem? For the moment it would be a great help if, wen the shadow is set to white, the lighting behaves like with the architectural glass posted by sharlybg.