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2.82 Denoising Data produces tile artifacts in Denoising Normal
Confirmed, NormalPublicBUG


OS: Win10 x64
GeForce GTX 960/PCIe/SSE2

Blender Version: 2.82 (sub 7), branch: master, commit date: 2020-03-12 05:06, hash: 375c7dc4caf4, type: Release
build date: 2020-03-12, 15:41:08
platform: Windows

"Short description of error" - yeah not really

I noticed

  1. tiled errors on water surface on multiple frames
  2. missing denoise on multiple frames

while rendering on SheepIT's distributed renderfarm, so I decided to investigate what's causing it. (blocks visible on water on the frame's lower side)

There are various other frames exhibiting the problem, rendered on various people's machines, so I decided to do a test render myself, and while not as pronounced the results did have a sort of similar error to them: (small error visible in the center, slightly upwards)

Second test to see if it was deterministic: (it's not, now the error is at the center penisula region both times)

It was caused by the Denoise Normal node providing part of a tile of misinformation:

Since the Denoise Normal data contains information on caustic and transparent surface's normals, and the error only occured on the edges of the water surface where I'm playing with transparency mixing, it made sense to try and disconnect the transparency part from the node tree, and lo and behold the error disappeared, along with the transparency, obviously.

Tested it out with the node hooked up with the diffuse mix, but the factor was 000.

And then with the opposite; 1:

And 0.5:

Redid the original value of 0.525 but it rendered out correctly...
Re-unzipped the entire thing and did a second render of the original values, sure enough there were artifacts.
Re rendered and it was fine.
Re rendered and it was there again.
Dialed the mix node to 0.5 again and there was the error again.

I'm guessing it's some sort of stupid float rounding error yielding a nan or null or zero value during the mixed transparency calculation of the normals behind the object.

As the file uses image sequences, I dont really want to start stripping out the parts and testing if I screw up, this is random enough as is.
Frame 44 has produced errors on the farm and several times on my pc aswell, so to test just dial in frame 44 and hit f12
If it's not very apparent just hook up the Denoise Normal node to the view in the compositor and look for the big white splotch.

47mb zip

Event Timeline

I can confirm white squares in denoising data when rendering on CPU

I have been 100% successful reproducing on frame 102 (as file was saved)
Also I removed all objects, but light, camera, BaseTerrain and WaterLevel

Further attempts to simplify material was unsuccessful. I got to point where I got only principled and transparent BSDF mixed 50/50 and still was able to reproduce. Error dissappeared on further attempt to simpilfy, and I haven't been able to reproduce even if I undo my changes.

Richard Antalik (ISS) changed the task status from Needs Triage to Confirmed.Apr 28 2020, 8:41 PM
Brecht Van Lommel (brecht) changed the subtype of this task from "Report" to "Bug".