LuxCoreRender Forums

Hi, in order to understand volumetrics i'm using with a very basic scene.
However I'm experiencing a strange behavior wen i apply the volumetrics to agemetry.

this is the scene without volumetrics: this is the scene with volumetrics applied to world
this is the scene with volumetrics applied to a box which is slightly bigger as the scene.
why the box version subtracts lighting to the scene without showing the light beams?
absorption color is pure white
detpth 10km
scattering color pure white
scale 0.1

From here you can download the last two luxcore scenes.
https://drive.google.com/drive/folders/ ... sp=sharing

Thanks for any help

daros wrote: ↑Fri Sep 17, 2021 10:01 am why the box version subtracts lighting to the scene without showing the light beams?

I assume you have not defined the inside/outside volumes of the walls: the rays starting from the the light sources hit the walls and, at that point, LuxCore try to deduce the volume the rays were traveling in but the walls say there was no inside/outside volume. This is a problem because the light sources are inside the volume box.

Word volume defines the default volume (when no more information are available) so when the rays hit the walls, they are assumed to have traveled inside the world volume.

So the problem is, that LuxCore can not deduce the volume where the light it traveling threw. So should define inside volume for all objects in the scene? Will it be correct or it will cause some problems?

i this moment the scene is set-up like this:
inside volume assigned only to the black box

It seem to be a Bidir only Issue , see the attached scene for understanding :

bartek_zgo wrote: ↑Fri Sep 17, 2021 11:35 am So the problem is, that LuxCore can not deduce the volume where the light it traveling threw. So should define inside volume for all objects in the scene? Will it be correct or it will cause some problems?

Yes, if you are not defining the world volume (aka the default volume when no other volume information are available).

Hi dade, but we defined a inside volume which contains the entire scene. In fact, as pointed out by sharlybg, under path tracing everything works well...only under bidir we have that issue.

daros wrote: ↑Fri Sep 17, 2021 4:29 pm Hi dade, but we defined a inside volume which contains the entire scene. In fact, as pointed out by sharlybg, under path tracing everything works well...only under bidir we have that issue.

As I wrote in my previous post, you need to define the inside/outside volume of the walls: a ray start from the light source hits a and has no information at all of the outside box, how could it have ?

In my opinion the problem is the lack of a feature: light sources currently have no "volume" property, so you can't tell them which volume they're in.

One moment... but why the scene works perfectly under path tracing?