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Cycles not rendering shadows on GPU when MotionBlur enabled
Open, Waiting for Developer to ReproducePublic


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: 87c017985719, 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



Event Timeline

Philipp Oeser (lichtwerk) lowered the priority of this task from Needs Triage by Developer to Needs Information from User.Sep 16 2019, 2:04 PM

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

Bastien Montagne (mont29) raised the priority of this task from Needs Information from User to Waiting for Developer to Reproduce.Tue, Oct 1, 9:29 PM

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 (, same version of 2.81.