Motion Blur in EEVEE is not blending steps properly for camera motion in newer versions #81752

New Issue

Cycles · 2020-10-16T02:41:27+02:00

Cycles commented

2020-10-16 02:41:27 +02:00

System Information
Operating system: Microsoft Windows 10 Pro
Graphics card: Nvidia GeForce GTX 1050
Processor: Intel(R) Core(TM) i5-2500 CPU @ 3.30GHz, 3301 Mhz, 4 Core(s), 4 Logical Processor(s)

Blender Version
Broken: blender-2.92.0-e4728d0a167c-windows64
Worked: New in 2.90, didn't work in older builds of 2.90

Short description of error
When there is very high camera motion blur in EEVEE, a step value greater than 1 introduces noticeable steps which don't get properly blended. There is some post-process blur but not enough to fill the gaps. Changing Max Blur or Background Separation doesn't help.

This bug was previously reported. I thought that the bug got fixed, but in reality time step blur was temporarily not working, making it look like the blending issue was not present. In the newest versions, the bug is now present again.

Exact steps for others to reproduce the error
Start with default blend file
Go to frame 1 and rotate the camera so the default cube is at the left of the screen
Add a keyframe (of rotation)
Go to frame 5 and rotate the camera so the default cube is at the right of the screen
Add another rotation keyframe
Turn on motion blur with steps set to 4
Render a still image at frame 3
Notice stepping artifacts not being blended properly by the post-process motion blur.

**System Information** Operating system: Microsoft Windows 10 Pro Graphics card: Nvidia GeForce GTX 1050 Processor: Intel(R) Core(TM) i5-2500 CPU @ 3.30GHz, 3301 Mhz, 4 Core(s), 4 Logical Processor(s) **Blender Version** Broken: blender-2.92.0-e4728d0a167c-windows64 Worked: New in 2.90, didn't work in older builds of 2.90 **Short description of error** When there is very high camera motion blur in EEVEE, a step value greater than 1 introduces noticeable steps which don't get properly blended. There is some post-process blur but not enough to fill the gaps. Changing Max Blur or Background Separation doesn't help. This bug was previously reported. I thought that the bug got fixed, but in reality time step blur was temporarily not working, making it look like the blending issue was not present. In the newest versions, the bug is now present again. **Exact steps for others to reproduce the error** Start with default blend file Go to frame 1 and rotate the camera so the default cube is at the left of the screen Add a keyframe (of rotation) Go to frame 5 and rotate the camera so the default cube is at the right of the screen Add another rotation keyframe Turn on motion blur with steps set to 4 Render a still image at frame 3 Notice stepping artifacts not being blended properly by the post-process motion blur. ![motionblurissue.png](https://archive.blender.org/developer/F8752571/motionblurissue.png)

Cycles commented

2020-10-16 02:41:27 +02:00

Added subscriber: @Cycles

Germano Cavalcante commented

2020-10-16 19:51:40 +02:00

Added subscribers: @fclem, @mano-wii

Germano Cavalcante commented

2020-10-16 19:51:40 +02:00

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

Germano Cavalcante commented

2020-10-16 19:51:40 +02:00

I tested it on different versions of 2.90 and got the same result.
What was the subversion of 2.90 that really worked? (you can share the System Info in Help -> Save System Info)

Here the file I used:
eevee_mblur_steps.blend

But compared to the images in the manual , 4 steps apparently should have a smoother transition.
So I'm not sure if the transition with 4 steps shown in the image is really expected. (@fclem?)

I tested it on different versions of 2.90 and got the same result. What was the subversion of 2.90 that really worked? (you can share the System Info in `Help -> Save System Info`) Here the file I used: [eevee_mblur_steps.blend](https://archive.blender.org/developer/F9000405/eevee_mblur_steps.blend) ---- But compared to the images in the [manual ](https://docs.blender.org/manual/en/latest/render/eevee/render_settings/motion_blur.html), 4 steps apparently should have a smoother transition. So I'm not sure if the transition with 4 steps shown in the image is really expected. (@fclem?)

Cycles commented

2020-10-16 20:39:11 +02:00

It never actually worked. There was just a version where I couldn't use multiple time steps due to a different bug (https://developer.blender.org/T79646). At first I didn't realize there was a bug, and no time steps meant no blending issues (since there were no steps to blend between) so I thought it was gone. The bug later got fixed (not this blending bug but the time step one) and the blending issues came back. The hash mentioned in the post is a93be410c9. So, even in that version the bug was not fixed. As far as I know, it has been there ever since the new motion blur was added. I hope I am clear.

Additional info: this bug only affects camera motion, if I do the exact same thing but changing location of the cube rather than camera position, it blends fine.

It never actually worked. There was just a version where I couldn't use multiple time steps due to a different bug (https://developer.blender.org/T79646). At first I didn't realize there was a bug, and no time steps meant no blending issues (since there were no steps to blend between) so I thought it was gone. The bug later got fixed (not this blending bug but the time step one) and the blending issues came back. The hash mentioned in the post is a93be410c9. So, even in that version the bug was not fixed. As far as I know, it has been there ever since the new motion blur was added. I hope I am clear. Additional info: this bug only affects camera motion, if I do the exact same thing but changing location of the cube rather than camera position, it blends fine.

Clément Foucault self-assigned this 2020-10-17 20:33:35 +02:00

Clément Foucault commented

2020-10-17 20:33:35 +02:00

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

blender-admin commented

2020-11-05 17:57:19 +01:00

This issue was referenced by aae60f0fec

This issue was referenced by aae60f0fecf74c93d8c6e8a5e33ffd4fb6c76a3a

Clément Foucault commented

2020-11-05 18:00:47 +01:00

Changed status from 'Confirmed' to: 'Resolved'

Clément Foucault closed this issue

2020-11-05 18:00:47 +01:00

Thomas Dinges added this to the 2.91 milestone 2023-02-08 16:20:10 +01:00

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Motion Blur in EEVEE is not blending steps properly for camera motion in newer versions #81752