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Blender overexposes Denoising Clean Pass in proportion to the amount of samples
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Description

System Information
Operating system: Ubuntu 18.04.1
Graphics card: RX 480

Blender Version

Broken:
blender-2.79-5d5070dd1232-linux-glibc224-x86_64
blender-2.80-9541ce2c261b-linux-glibc224-x86_64

Worked:
-blender 2.79.6, 71211-111179beb0b-0thomas~bionic0, 2018-12-27
-Enabling denoise for all types of lights, that nullifies the functionality of this pass
-or dividing by a factor that is scene dependent

Short description of error
Denoising Clean Pass used to show the type of light that was disabled in the denoising panel correctly, now it overexposes erratically the pass with a multiplier of x128, or at least in the simple example of the blend file I appended, In the work that I noticed this bug the multiplier was around 5x

Exact steps for others to reproduce the error

  1. Make Sphere
  2. Set a SSS shader mixed with a diffuse shader
  3. Enable Denoising Passes, DiffCol, DiffInd, DiffCol passes, disable Diff direct and Diff indirect in denoising panel
  4. Render
  5. In compositor, Add DiffDir, DiffInd, then multiply with DiffCol, this image should be equal to Denoising Clean, but it's multiplied by x128
  6. In the example is multiplied by 1/128 to point out the overexposure.

Event Timeline

Sebastian Parborg (zeddb) lowered the priority of this task from Needs Triage by Developer to Confirmed, Medium.

2.79 (02-15):

2.8 (todays build):

iszotic (iszotic) renamed this task from Blender overexposes erratically Denoising Clean Pass to Blender overexposes Denoising Clean Pass in proportion to the amount of samples.Mar 6 2019, 7:32 PM

Blender is multiplying the number of render samples to the denoise clean pass

32 samples, raw output of denoise clean pass


32 samples, (Diff Dir + Diff Ind) * Diff Col

The zip file contains more examples of renders with 1 2 4 8 and 16 samples, and how the denoise clean pass gets more and more exposed,