How to use interior and exterior volumes?

[xlxs]

I was experimenting with lux but I couldn' t make an object's volume with a higher priority replace an others which overlaps, I'm also new to lux so probably I'm missing something easy, also I searched a bit in the wiki, but couldn't find much about interior/exterior. Uploaded an image describing the scene setup.Uploaded blend file(with a slightly smaller object).

[CodeHD]

Something that springs to my eye is this: The two objects seem to have the exact same size. In other words, the outer surface areas really lie in the same plane. Try to make the cube with the lower volume priority (!) smaller.
This is an issue in other places in blender, too. E.g. when you sue the boolean operators.

Btw it is always best to upload a blend-file with a question so that others can test on their system and play around with settings.

[xlxs]

Something that springs to my eye is this: The two objects seem to have the exact same size. In other words, the outer surface areas really lie in the same plane. Try to make the cube with the lower volume priority (!) smaller.
This is an issue in other places in blender, too. E.g. when you sue the boolean operators.

Btw it is always best to upload a blend-file with a question so that others can test on their system and play around with settings.

Uploaded the blend file with the cube (with the least priority slightly smaller) but now I think, the opposite happens, the green cube replaces reds volume (green has priority 2, red has 3).

[CodeHD]

Ok I still have a problem with the volume priority in this scene, too. No idea right now if this is a LuxCore or settings issue...

While playing around I did change some settings because I noticed a couple of things I would not have set up that way (and behaved differently). So just a few comments. Apologies If you have been aware of these and your scene was intentional

1) The matte matieral with 0 opacity doesn't seem to work in combination with volumetric effect. Give your cubes a glass matieral instead.
2) In any case, opacity=0 ont he matieral is not exactly "physical", so make sure you know what that means.

Regarding the colors, kep the following in mind:

3) Absorption depth and -color work in this way: After the absorption depth, it has been converted to the absorption color. White light though a red absorption color comes out red. So if you overlap red and green absorption (which happens here because we have a "small" green cube with a red boundary around it) with too short absorption depths, it will end up black.
4) For scattering, the scattering color is removed. Passing though red and green scattering would leave blue light transmitted.

[xlxs]

Thanks for the help , but I still can't get it to work (changed both to glass and tried with and without opacity)

[wasd]

Thanks for the help , but I still can't get it to work (changed both to glass and tried with and without opacity)

Me too.
Left: greatly overlaps, middle: slighly overlaps, right: not overlapping.

It seems volumes do not obey priority.

[Dade]

First of all it looks like there is a bug in BlendLuxCore and volume priority is always exported as 0, @B.Y.O.B

Than:

1) you need to lower the ground plane in order to not have a "Z fight" (aka numerical precision problems) between the lower face of the box and the ground plane.

2) Material "transparency" makes everything, including the volume, transparent. I assume it is not what you want. Just set the material to "null" and leave "transparency" unplugged.

3) I have removed the scattering (note: multi-scattering makes the rendering very slow) and done a test by hand setting the volume priorities. This is a rendering when green box has an higher priority:

and this when the red box has an higher priority:

So it works as expected if the priorities are correctly set.

[B.Y.O.B.]

First of all it looks like there is a bug in BlendLuxCore and volume priority is always exported as 0, @B.Y.O.B

Crazy that nobody noticed for so long.
I fixed the bug.

[xlxs]

Woot that was fast bug fixing, thank's B.Y.O.B.