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CYCLES: Surfaces inside volumes are Not Lit or Shadowed by the volume if the volume is not visible to Camera Rays
Open, Confirmed, LowPublic

Description

Linux Mint Mate
GTX 1050

Blender 2.81 Alpha
2019-09-27 22:44
Hash: 1c1a3198af9d

Discovered while trying to catch shadows from volumes on surfaces for compositing.

Surfaces inside of volume meshes are not shaded (lit/shadowed) by the volume if the volume is invisible to camera rays
(checkbox in Object Properties -> Visibility -> Ray Visibility -> Camera)
As far as i can tell this also affects Holdout.

Current workaround: make sure volume IS visible to camera rays, and instead bypass it in the volume shader using the Camera Ray socket on the Light Path node

To Reproduce:

Open attached .blend , press render
Note the missing shadow/light where the volume cubes intersect the default cube.

I have in the .blend also included the "expected behaviour" by using the workaround, switch the Scene from "Bug" to "Workaround" and press render again.
Note the shadow/light now covers the default cube properly.

Details

Type
Bug

Event Timeline

Brecht Van Lommel (brecht) lowered the priority of this task from Needs Triage by Developer to Needs Information from User.Wed, Oct 2, 6:48 PM

It seems the .blend file didn't get attached?

strange, the download link worked in the report preview. I have tried again.

Brecht Van Lommel (brecht) raised the priority of this task from Needs Information from User to Needs Triage by Developer.Wed, Oct 2, 11:15 PM
Germano Cavalcante (mano-wii) lowered the priority of this task from Needs Triage by Developer to Confirmed, Low.

I can confirm.
You can easily observe by selecting one of the invisible objects and enabling the Ray Visibility Camera option.