Cycles not rendering shadows on GPU when MotionBlur enabled #69916

System Information
Operating system: Windows 10 Pro 1903 (18362.356)
Graphics card: Radeon 5700XT

Blender Version
Broken: 2.81 (sub 11), branch: master, commit date: 2019-09-15 10:29, hash: 87c0179857, type: Release

Short description of error
Shadows not rendered when Motion blur enabled (cycles)

Exact steps for others to reproduce the error
As far as I can tell, this only happens on GPU rendered tiles. When rendering with CPU+GPU OpenCL scene, the tiles rendered by a CPU have shadows, tiles rendered by the GPU have not.

As you can see on the picture, there are no shadows. By rendering it again I watched which tiles are rendered by what device and I found out it is only GPU. Tiles render in same order every time, so the same spot on a image had no shadows rendered.

Image (I highlighted missing shadows):

Source of light: Sun and one other light

Added subscriber: @Wor3d

Added subscriber: @lichtwerk

Just to be sure we are all on the same page [this might depend on certain settings]:

could you share your .blend file where this happens?

Yes sure, frames 320-400
L_sizes showcase.blend

I am afraid I cannot reproduce this...

The only frame that seems off is frame 400 [it is one frame before the camera makes a drastic "cut"] where motion blur goes bunkers [but that happens on both CPU & GPU for me -- and is more or less expected, since the camera makes a jump (would advise to use two cameras here and work with camera markers here...)]

I will try to dig deeper and produce simplistic deterministic case. I had problems with Motion blur on other PC also, where it just straight crashed when GPU tried to render the frame (https://developer.blender.org/T69908), same version of 2.81.

Added subscriber: @iss

Changed status from 'Needs Developer To Reproduce' to: 'Needs User Info'

Is this still an issue with latest build? https://builder.blender.org/download/

Changed status from 'Needs User Info' to: 'Archived'

Since last asking for information it has been 7 or more days, due to the policy of our bug tracker we will have to close the report

Hi, still an issue. 2.82.7. We have been working on other project files, and the issue remains. CPU and Eevee renders it just fine, also rendered preview (on GPU...) works! Actual cycles render fails to render >any< shadow

Changed status from 'Archived' to: 'Needs User Info'

@Wor3d Can you check if this happens with 2.83 version still? Please make sure, that your driver is up to date and before testing click on File > Defaults > Load Factory Settings.

Hello, on version 2.83 (April 11th alpha) I am unable to start the render on the GPU.
The window "blender render" opens, but nothing happens, I don't see the status bar (loading kernels, etc.).
CPU is fully loaded on one core only (so ~7%), and no excess GPU/CPU memory is used.
On my other computer, the render works just fine on that project.

To the problematic one - we DDu'd (safe mode, etc.) the driver and installed the latest AMD driver (20.4.1). We loaded factory settings.

Changed status from 'Needs User Info' to: 'Needs Triage'

@Wor3d this issue seems to be reported, so I guess you can subscribe to #74262 so you will be notified when it will be resolved, than you can re-test this one. I will leave it open in meanwhile.

Thanks, I will keep an eye on it. Hopefully it will solve this problem too... Having to render on a CPU is a real slow-down :/

If I can somehow help (etc. enable/set verbosity and dig through some debug logs?), just point me how/where to do it, I am fluent in programming languages and so, but not Python and OpenGL in particular..., but I am sure I can dig through it :) I am just helping to solve this problem for my brother, who actually uses the machine for work.

In #69916#909714, @Wor3d wrote:
If I can somehow help (etc. enable/set verbosity and dig through some debug logs?), just point me how/where to do it, I am fluent in programming languages and so, but not Python and OpenGL in particular..., but I am sure I can dig through it :) I am just helping to solve this problem for my brother, who actually uses the machine for work.

I could imagine that help would be appreciated. I am not exactly sure what the issue is there, it may be bug in driver, that is hard to work around. I would recommend offering help / asking for info in particular thread or in https:*blender.chat or https:*devtalk.blender.org

blender-2.90-00e0034b13e6 (windows 64)

Fixed my problem! Wow :) Shadows are now properly rendered with GPU and motion blur. Can't wait for stable release.

Thanks, whatever fixed it, shall it not break again 🤞

Changed status from 'Needs Triage' to: 'Resolved'

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Cycles not rendering shadows on GPU when MotionBlur enabled #69916