Volume renderpass issue

[Dizern]

A. Windows 8.1 Pro/Win 10 Pro (I've tried on several PCs)
B. 2x GTX 1080/7x GTX 1080/8x GTX 1070
C. 32GB
D. 21.21.13.7878
E. 3.06
F. 3.06
G. Maxon Cinema 4D 18.048/ Maxon Cinema 4D 18.057

H. Recently I tried to export dusty barn render with multipass to compose it later. But the composed footage just doesn't look even close to the main beauty. There was something with volume.
After a week of tests, I've found that bounced light rays just doesn't work right with volume in renderpasses. I run many tests, but to demonstrate it in the clearest way, I've built a simple scene:

The top is closed by a plane

Beauty render

So, all the only light coming through the holes is bounced from a wall. Therefore, diffuse direct should be black(PT/PMC):

Diffuse Direct

2.png (5.71 KiB) Viewed 1747 times

Ok, it is, let's go forward. As I do not use any glossy/spec materials, all the info should be stored in Diffuse indirect pass(and be a copy of the beauty), but it's not:

Diffuse indirect

I've tried to render out all passes and compose them — no result. I've tried different color spaces, formats, bitrate — no result. Everything is identical even in octane preview.
Here's comparison:

Comparison

Scene file:

Volume Multipass test.7z

Scene FIle

(14.46 MiB) Downloaded 166 times

[aoktar]

Thanks for detailed report but, you look like missed the first rule of working with passes.
You should not compare linear compositing results with tonemapped results of Live Viewer.

1- First change tonemapping to linear/gamma 2.2 and vignetting=0 for camera imager for Live Viewer results.
2- Change render buffer to linear, don't use tonemapped buffers for working with passes. You should apply a similar tonemapping in a post software on composited passes.
Btw i'm not sure about volume medium's effect on diffuse pass. Diffuse pass looks like does not correctly display the scatter effect of medium. Reported!

[abstrax]

Thanks for the report. It seems Octane is not recording the contribution of volumes in the SSS pass. We will look into it and fix it as soon as possible.

[Dizern]

[quote="aoktar"]Thanks for detailed report but, you look like missed the first rule of working with passes.
You should not compare linear compositing results with tonemapped results of Live Viewer.

I compared tonemapped with tonemaped pics(As I remember). Linear workflow(I use BM Fusion and After Effects) gives a different picture, but the same result of volume SSS. But thanks for the hint nevertheless!