Black Artefacts / Negative Pixels with Denoiser #51681

New Issue

Steffen Dünner · 2017-05-31T12:57:52+02:00

Steffen Dünner commented

2017-05-31 12:57:52 +02:00

System Information
Win10 x64 1703 / nVidia GTX 780 3GB

Blender Version
Broken: All builds with denoiser so far
Worked: none

Short description of error
Black visual artefacts in rendering after denoising. The pixels show negative RGB values. The results look much much better with Branched Path Tracing even with lower number of samples.
I attached a super-simplified scene. The production scene it was made from shows loads more artefacts like this.

Path Tracing:

Branched Path Tracing:

Exact steps for others to reproduce the error

Load blend file
Press F12 -> Black outlines appear
Switch render method to "Branched Path Tracing"
Press F12 again -> No artefacts (or much less artefacts depending on specific scene)

TEASER_SHOT02_v17_TO_SUPPORT.blend

**System Information** Win10 x64 1703 / nVidia GTX 780 3GB **Blender Version** Broken: All builds with denoiser so far Worked: none **Short description of error** Black visual artefacts in rendering after denoising. The pixels show negative RGB values. The results look much much better with Branched Path Tracing even with lower number of samples. I attached a super-simplified scene. The production scene it was made from shows loads more artefacts like this. Path Tracing: ![Denoise_Path.png](https://archive.blender.org/developer/F614061/Denoise_Path.png) Branched Path Tracing: ![Denoise_Branched_Path.png](https://archive.blender.org/developer/F614060/Denoise_Branched_Path.png) **Exact steps for others to reproduce the error** - Load blend file - Press F12 -> Black outlines appear - Switch render method to "Branched Path Tracing" - Press F12 again -> No artefacts (or much less artefacts depending on specific scene) [TEASER_SHOT02_v17_TO_SUPPORT.blend](https://archive.blender.org/developer/F614065/TEASER_SHOT02_v17_TO_SUPPORT.blend)

Steffen Dünner commented

2017-05-31 12:57:52 +02:00

Changed status to: 'Open'

Steffen Dünner commented

2017-05-31 12:57:52 +02:00

Added subscriber: @SteffenD

Joel Godin commented

2017-05-31 16:18:24 +02:00

Added subscriber: @FloridaJo

Lukas Stockner was assigned by Joel Godin

2017-05-31 16:18:24 +02:00

Joel Godin commented

2017-05-31 16:18:24 +02:00

Confirmed. Goes away when direct and indirect clamp is below 30.

Steffen Dünner commented

2017-05-31 16:26:17 +02:00

Yes, I noticed that too. The bundled EXR environment seems to be a tough one. The tiny sun disk is at something around 50000 RGB!
But on the other hand I want / need the "power" of this sun to give me bright highlights and sharp shadows, clamping would be my last resort.
I wonder why Branched PT isn't giving me artifacts.

Yes, I noticed that too. The bundled EXR environment seems to be a tough one. The tiny sun disk is at something around 50000 RGB! But on the other hand I want / need the "power" of this sun to give me bright highlights and sharp shadows, clamping would be my last resort. I wonder why Branched PT isn't giving me artifacts.

Lukas Stockner commented

2017-06-11 02:04:29 +02:00

Changed status from 'Open' to: 'Archived'

Lukas Stockner closed this issue

2017-06-11 02:04:29 +02:00

Lukas Stockner commented

2017-06-11 02:04:29 +02:00

Okay, this is somewhat improved with 558bea2. I'll look into better handling in the future, but we're really close to a release and fixing the underlying issues will be really tricky (if it's even possible)...

I'll close this for now, but I'll keep the file for further tests.

(Sorry for the copy-paste from other reports, these are all related issues).

Specifically for this scene, the SSS is handled much better by BPT which causes lower variance and therefore more stable reconstruction. Try lowering the BPT sample count and you'll get the same artifacts.

Okay, this is somewhat improved with 558bea2. I'll look into better handling in the future, but we're really close to a release and fixing the underlying issues will be really tricky (if it's even possible)... I'll close this for now, but I'll keep the file for further tests. (Sorry for the copy-paste from other reports, these are all related issues). Specifically for this scene, the SSS is handled much better by BPT which causes lower variance and therefore more stable reconstruction. Try lowering the BPT sample count and you'll get the same artifacts.

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Black Artefacts / Negative Pixels with Denoiser #51681