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Denoise + File Output nodes: freezing at 99% of render
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System Information
macOS Sierra 10.12.4
Processor: 2.8 GHz Intel Core i7
Memory: 8 GB 1067 MHz DDR3
Graphics: ATI Radeon HD 4850 512 MB

Blender Version
Broken: 2.78 0021268311
Worked: N/A (new feature)

Short description of error
When Cycles' Denoise is used with the File Output node Blender is often freezing at 99%.
Blender becomes unresponsive and requires a Force Quit.
No file is written, neither to the directory specified in the Output settings nor to the directory specified in the File Output node.

In my experience it doesn’t freeze when Denoise is off.

It is more likely to crash when rendering at higher resolutions than lower.
When I rendered at 10% resolution, frame 1 was able to render, but frame 2 still crashed even at the very low resolution.
However, I was finally able to render all frames at 10% when I tried later in the day. Perhaps because the memory usage by other applications was lower then. Rendering at higher resolutions still failed though.
I have never had success rendering all three frames at full HD (1920x1080). I have sometimes had success rendering all three frames at 10% (of 1920x1080).

It doesn’t crash when the File Output node is removed.
This seems to indicate a connection with the freezing at 99%, because it is at the end of the render when File Output is used.

I am attaching a .blend file for testing. The render resolution is presently at 10% of 1920x1080 for speedy troubleshooting, but if it doesn't freeze at the ultra-low resolution, try something higher.
The purpose of the .blend was to try lighting a simple indoor scene with an environment to see how much Denoise can help with this typically noisy task. (It helps a lot! I was amazed.)
The .blend has 3 frames of animation with the only difference being the exposure.
I added a File Output node because I wanted my stills to output a file just the same as animation.
I wasn't setting out to find bugs, but since that happened, hopefully the .blend can useful for debugging.
I should mention that this is the second time I've created a denoised environment-lit indoor scene like this, and both resulted in freezing after rendering 99%. It's not a one-time fluke.

Finally, I found that knocking out just about all of the materials stopped the freezing, but it's not much of a solution, and still doesn't explain the 99%.

Exact steps for others to reproduce the error

  1. Set render engine to Cycles.
  2. Model an indoor scene where light can enter through windows.
  3. Assign some materials.
  4. Add environment lighting.
  5. Enable the Denoise option.
  6. In the Compositor, connect a File Output node.
  7. Render a still or an animation, and see if Blender freezes at 99%.



Event Timeline

Update: I was able to reproduce the same result on another machine with the following specs:

macOS Sierra 10.12.5
Processor: 2.8 GHz Quad-Core Intel Xeon
Memory: 16 GB 1066 MHz DDR3
Graphics: ATI Radeon HD 5770 1024 MB

I opened the .blend, specified the output directories, and tried to render as an animation (leaving the render resolution low). On the first frame Blender became unresponsive at 99%.

Seth L. (quantumanomaly) renamed this task from Deniose + File Output nodes: freezing at 99% of render to Denoise + File Output nodes: freezing at 99% of render.Jun 5 2017, 5:29 AM
Sergey Sharybin (sergey) lowered the priority of this task from Needs Triage by Developer to Normal.Jun 6 2017, 11:53 AM

I can't reproduce the issue on Linux, maybe this is a Mac-specific problem?

If yes, it would be great if someone who can reproduce this on Mac could do so in a debug build and give me a backtrace of the freezing thread(s).

Wasn't able to reproduce on my mac.

@Lukas Stockner (lukasstockner97) I would be happy to. Where can I find a "debug build"? This is the first time I've heard of this type of build; pardon my ignorance.