layer black shadow show any shadow project by lights even the light source is blocked by polygon.And the shadow intensity is controlled by light sampling rate in octane light tag.
Below scene I set the tube layer 2 and others are layer 1,and here is the render setting and 2 different scenes
scene 1 with 1 light
sence 1 tube shadow
scene 2 with 2 lights
scene 2 tube shadow
scene 2 tube shadow with 5 sampling rate for left light and 1for right light. both lights have same light power and other attributes
The left light should not project shadow because it is blocked by the middle pane, but the LBSH layer seems like there is no block between tube and the left light. And shadow intensity is affect by sampling rate. Those bugs really annoy me when compositing. I hope these can be fixed soon.
A.Win10
B.GTX1080ti
C.48GB
D.398.11
E.not installed
F.3.08
G.c4d R19