Shadow catcher receive shadows even if there is no light in the scene #69410

New Issue

Christoph Werner · 2019-09-02T15:04:09+02:00

Christoph Werner commented

2019-09-02 15:04:09 +02:00

System Information
Operating system: Windows
Graphics card: GeForce GTX 1080 Ti

Blender Version
Broken: version: 2.80 (sub 75), branch: master, commit date: 2019-07-29 14:47, hash: f6cb5f5449, type: build date: 2019-07-29, 09:44 AM
Worked: -

Short description of error
See my attached .blend file for an example and the screenshot for additional infos.

If you set the light object power to "0", then the shadow catcher object receives shadows. But there is no light in the scene.
I've set the world light to "0" too. This should not happen.

Exact steps for others to reproduce the error

Open my blend file.
Set one of the top views to "Rendered". Use the Cycles renderer.
Set the light power to "0" now.
The shadow catcher on the ground receives shadows then, but there is no light in the scene anymore. This isn't what I expect. Actually there shouldn't be any shadows around the box.

Do I misunderstand something when using the shadows catcher or is this an error?

shadowcatcher_problem01.blend

**System Information** Operating system: Windows Graphics card: GeForce GTX 1080 Ti [system-info.txt](https://archive.blender.org/developer/F7714186/system-info.txt) **Blender Version** Broken: version: 2.80 (sub 75), branch: master, commit date: 2019-07-29 14:47, hash: f6cb5f54494e, type: build date: 2019-07-29, 09:44 AM Worked: - **Short description of error** See my attached .blend file for an example and the screenshot for additional infos. If you set the light object power to "0", then the shadow catcher object receives shadows. But there is no light in the scene. I've set the world light to "0" too. This should not happen. **Exact steps for others to reproduce the error** - Open my blend file. - Set one of the top views to "Rendered". Use the Cycles renderer. - Set the light power to "0" now. - The shadow catcher on the ground receives shadows then, but there is no light in the scene anymore. This isn't what I expect. Actually there shouldn't be any shadows around the box. Do I misunderstand something when using the shadows catcher or is this an error? ![shadow_catcher_problem01.jpg](https://archive.blender.org/developer/F7714260/shadow_catcher_problem01.jpg) [shadowcatcher_problem01.blend](https://archive.blender.org/developer/F7714188/shadowcatcher_problem01.blend)

Christoph Werner commented

2019-09-02 15:04:09 +02:00

Added subscriber: @ChristophWerner

Marcin Twarowski commented

2019-09-02 15:55:25 +02:00

Added subscriber: @MarcinTwarowski

Marcin Twarowski commented

2019-09-02 15:55:25 +02:00

This comment was removed by @MarcinTwarowski

*This comment was removed by @MarcinTwarowski*

Philipp Oeser commented

2019-12-29 13:31:05 +01:00

Added subscribers: @Sergey, @lichtwerk

Philipp Oeser commented

2019-12-29 13:31:05 +01:00

Changed status from 'Needs Triage' to: 'Confirmed'

Philipp Oeser commented

2019-12-29 13:31:05 +01:00

Although a bit on shaky ground here, but I would kind of confirm this issue.

Relevant commits:
d14e39622a
bd069a89aa

For absolutely no light (path_total == 0.0f), bd069a89aa changed behavior from returning 1.0f to returning L->shadow_transparency (see what is now path_radiance_sum_shadowcatcher).
Since above commit was only intended to fix problems with transparent shadow casters, but also changed the behavior for opaque shadow casters in the case of no light, I would assume this can somehow be fixed and was not intended, @Sergey?
(to me it would make more snese to actually have no shadow in the case of no light -- so agree with the report, but will leave up to @Sergey to decide.... confirming for now though...)

Sidenote: there are all sorts of (other) improvements to make, so if this turns out to be a known limitation for now, maybe this can be considered elswhere:
https://devtalk.blender.org/t/lets-finally-fix-the-shadowcatcher/691
#71253 (Cycles shadow catcher improvements)

Although a bit on shaky ground here, but I would kind of confirm this issue. Relevant commits: d14e39622a bd069a89aa For absolutely no light (`path_total == 0.0f`), bd069a89aa changed behavior from returning 1.0f to returning `L->shadow_transparency` (see what is now `path_radiance_sum_shadowcatcher`). Since above commit was only intended to fix problems with transparent shadow casters, but also changed the behavior for opaque shadow casters in the case of no light, I would assume this can somehow be fixed and was not intended, @Sergey? (to me it would make more snese to actually have no shadow in the case of no light -- so agree with the report, but will leave up to @Sergey to decide.... confirming for now though...) Sidenote: there are all sorts of (other) improvements to make, so if this turns out to be a known limitation for now, maybe this can be considered elswhere: https://devtalk.blender.org/t/lets-finally-fix-the-shadowcatcher/691 #71253 (Cycles shadow catcher improvements)

Christoph Werner commented

2020-01-16 08:30:55 +01:00

Exactly. I repeat it for better understanding:

If there is no world light set (environment light strength is set to 0 )
and there is no light object set or all light objects are set to power of 0 then no shadows should be seen on any shadow catchers.

For me this is often a problem, when I work with render passes.

Thank you for the attention
Chris

Exactly. I repeat it for better understanding: If there is no world light set (environment light strength is set to 0 ) and there is no light object set or all light objects are set to power of 0 then no shadows should be seen on any shadow catchers. For me this is often a problem, when I work with render passes. Thank you for the attention Chris

Brecht Van Lommel commented

2021-11-05 22:28:26 +01:00

Added subscriber: @brecht

Brecht Van Lommel commented

2021-11-05 22:28:26 +01:00

Changed status from 'Confirmed' to: 'Archived'

Brecht Van Lommel closed this issue

2021-11-05 22:28:26 +01:00

Brecht Van Lommel commented

2021-11-05 22:28:26 +01:00

The rewritten shadow catcher in Blender 3.0 does not have this problem anymore.

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Shadow catcher receive shadows even if there is no light in the scene #69410