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Does not work when collection 'holdout' is set to 'indirect only'
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Description

System Information
Operating system: MacOS10.14.5
Graphics card: AMD Radeon Pro 580X OpenGL Engine ATI Technologies Inc. 4.1 ATI-2.9.26

Blender Version
Broken: version: 2.80 (sub 74), branch: master, commit date: 2019-07-02 22:33, hash: rB50ccbe6bb233
Worked: (optional)

Short description of error
Previously reported, but the latest version has not been fixed
Report again with the video file, as the previous report does not recognize the problem

Does not work when collection 'holdout' is set to 'indirect only'

Exact steps for others to reproduce the error

  1. Register an object in the collection
  2. Set the holdout for that collection
  3. Render (holdout works)
  4. Set "indirect only" of the collection in that state
  5. Render (holdout does not work, only "indirect" works)

Event Timeline

This looks like the expected behavior to me. "Indirect Only" means that the collection casts shadows and reflections, but does not appear directly. If the object appeared as a holdout, that would be direct shading.

What is the result you were expecting?

Sam Brubaker (rocketman) lowered the priority of this task from Needs Triage by Developer to Needs Information from User.Jul 3 2019, 5:24 AM

I agree that this looks like a bug, or at least it's not the logical behavior.
I would expect Holdout to "override" Indirect Only.
With Indirect Only you see only the indirect influence of the object.
With Holdout you see the indirect influence of the object to the scene, but also it cuts a hole in the render, so to speak.
So funtionality wise Indirect Only is included in Holdout. So if both are activated, I think it should be rendered as holdout.

As I know its not intended to check indirect only and holdout together?!

My opinion is simple
If Holdout is on, "Holdout" should work
If "indirect only" takes precedence, "Holdout" should be turned off automatically in the UI
It is very difficult to understand that it doesn't work even though "Holdout" is on
This is the same even if "Holdout" is given priority
In that case, "indirect only" should be turned off automatically
It should be clearly indicated on the UI that only one side can be used like an electrical switch

I also want to ask
Why did you create a UI that can turn both on, but only one can be used?
If you can only use one, you should change the UI

a (box_channel) added a comment.EditedJul 3 2019, 4:32 PM

This is the video of blender2.79b
I think the same situation as setting "Indirect only" and "Holdout" in blender 2.8 at the same time, but "Holdout" is working
Why did the behavior change in blender 2.8?
This is the reason I think is a bug

Sam Brubaker (rocketman) raised the priority of this task from Needs Information from User to Needs Triage by Developer.Jul 4 2019, 2:42 AM

I understand now, and I agree that this is not ideal behavior.

I also noticed another regression related to this matter: In 2.7, it is possible to use a layer as a holdout without indirectly affecting the scene by using the Exclude feature:

It is common to want a holdout that does not contribute indirectly to the render, but there is no easy way of doing this in 2.8! You can disable the ray visibility for each object in the collection, but that is tedious and interferes with those objects being rendered elsewhere. Perhaps a solution could be implemented that fixes both these issues:

If "Holdout" is enabled for a collection, then the function of the "Indirect Only" setting should change, so that the collection either does or does not contribute indirectly to the scene.

I will leave this decision to a developer.

@Brecht Van Lommel (brecht): is this something you could look at or decide upon?

  • 2.8 holdout + indirect only: looks like a bug to me [I am with @Sebastian Koenig (sebastian_k) here]
  • 2.79 exclude + mask "feature missing": this apparently already changed from 2.79b to 2.79 branch? (in the current branch, seems like setting a layer to both exclude and mask will at least render it's shadows...)
Philipp Oeser (lichtwerk) lowered the priority of this task from Needs Triage by Developer to Waiting for Developer to Reproduce.Jul 4 2019, 2:50 PM
Brecht Van Lommel (brecht) lowered the priority of this task from Waiting for Developer to Reproduce to Confirmed, Medium.

The behavior regarding exclude is a known limitation at the moment, there is a comment in the code about it. The dependency graph does not evaluate the excluded objects at all so this requires a different design.

The holdout + indirect only behavior I can fix.