Exterior world exposure of scene, rendered with HDRI, changes, gets darker and flat, when points lights are rendered inside building model. #53585

New Issue

Aaron Smithey · 2017-12-19T05:47:52+01:00

Aaron Smithey commented

2017-12-19 05:47:52 +01:00

System Information
Windows 7 x64 GTX 970
dual E5 2660 v3's (2.6 ghz) (40 Threads) Z10PE D8 WS, 96 gigs of ram

Blender Version
Blender 2.79 5bd8ac9

Short description of error17026-1-Roedo CDJR_12-13-17.zip

This has happened on all my larger projects using 2.79.
Using the attached file......
Render one view, exterior camera view, with point lights off. This is the correct exposure.
Render another view, exterior camera view, with the point lights on, the view is bad.
Notice the difference in the two rendered views.
When points lights are on, the image is dark and flat looking.

Thanks,

Aaron

**System Information** Windows 7 x64 GTX 970 dual E5 2660 v3's (2.6 ghz) (40 Threads) Z10PE [D8](https://archive.blender.org/developer/D8) WS, 96 gigs of ram **Blender Version** Blender 2.79 5bd8ac9 **Short description of error**[17026-1-Roedo CDJR_12-13-17.zip](https://archive.blender.org/developer/F1451169/17026-1-Roedo_CDJR_12-13-17.zip) This has happened on all my larger projects using 2.79. Using the attached file...... Render one view, exterior camera view, with point lights off. This is the correct exposure. Render another view, exterior camera view, with the point lights on, the view is bad. Notice the difference in the two rendered views. When points lights are on, the image is dark and flat looking. Thanks, Aaron

Aaron Smithey commented

2017-12-19 05:47:52 +01:00

Added subscriber: @AaronSmithey

Sergey Sharybin commented

2017-12-20 12:02:35 +01:00

Added subscribers: @brecht, @Sergey

Sergey Sharybin self-assigned this 2017-12-20 12:02:35 +01:00

Sergey Sharybin commented

2017-12-20 12:02:35 +01:00

Here is a much simpler file: T53585_simple.blend

Using branched path tracing with "Sample All Light" solves the issue.

@brecht, is it a missing/wrong MIS weight when some lights are not visible? Can have a closer look later..

Here is a much simpler file: [T53585_simple.blend](https://archive.blender.org/developer/F1463917/T53585_simple.blend) Using branched path tracing with "Sample All Light" solves the issue. @brecht, is it a missing/wrong MIS weight when some lights are not visible? Can have a closer look later..

Aaron Smithey commented

2017-12-21 07:40:18 +01:00

So, this behavior while rendering with path tracing is abnormal? Is this indeed a bug?

Brecht Van Lommel commented

2017-12-24 15:53:58 +01:00

It's almost certainly a bug, we need to investigate the cause still.

Brecht Van Lommel commented

2017-12-26 00:14:43 +01:00

Changed status from 'Open' to: 'Archived'

Brecht Van Lommel closed this issue

2017-12-26 00:14:43 +01:00

Brecht Van Lommel commented

2017-12-26 00:14:43 +01:00

Actually, there seems to be no bug here. Direct light sampling clamping is set to 5.0, which is much too low for this scene. If clamping is disabled then path and branched path converge to the same results, which seems correct to me.

In general sample clamping should only be used as a last resort to kill noise, and preferably only for indirect light. It's completely biased and scene dependent, and the appropriate value needs to be tweaked for every scene. We might add a smarter clamping at some point, but there is no bug here it seems.

Actually, there seems to be no bug here. Direct light sampling clamping is set to 5.0, which is much too low for this scene. If clamping is disabled then path and branched path converge to the same results, which seems correct to me. In general sample clamping should only be used as a last resort to kill noise, and preferably only for indirect light. It's completely biased and scene dependent, and the appropriate value needs to be tweaked for every scene. We might add a smarter clamping at some point, but there is no bug here it seems.

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Exterior world exposure of scene, rendered with HDRI, changes, gets darker and flat, when points lights are rendered inside building model. #53585