Motion blur steps value incorrectly changes shutter duration and affects AA quality #79672

New Issue

Paul R · 2020-08-09T20:30:58+02:00

Paul R commented

2020-08-09 20:30:58 +02:00

System Information
Operating system: SUSE Leap 15.1
Graphics card: NVidia RTX 2070 Super (official drivers)

Blender Version
Broken: 2.90, a93be410c9, x86_64 linux, 2020-08-07
Worked: 2.90, c5b6b3d82f, x86_64 linux, 2020-08-05
Issue introduced by: {4f59e4bddcb0c06e441adf68a5f252a4e5b4b260}

Short description of error
When the motion blur 'steps' value is set to any value greater than 1 it incorrectly changes the shutter duration and also affects the anti-aliasing quality. From this and the lack of blur on the animated texture strip, it looks like the sampled aspect isn't working.

Incorrrect:

Correct:

Exact steps for others to reproduce the error

load the attached .blend
choose an intermediate frame between 1 and 10
set steps value to 1 and render - motion blur duration and AA appear correct
set steps value to 4 and render - motion blur duration is reduced by a factor of 4 and AA samples is noticeably worse
set steps value to 32 - motion blur is all but gone and AA is poor
In earlier builds of 2.90 (eg c5b6b3d82f) the animated texture line would be correctly blurred

motion_blur_steps_value_v0.2.blend

**System Information** Operating system: SUSE Leap 15.1 Graphics card: NVidia RTX 2070 Super (official drivers) **Blender Version** Broken: 2.90, a93be410c974, x86_64 linux, 2020-08-07 Worked: 2.90, c5b6b3d82f56, x86_64 linux, 2020-08-05 Issue introduced by: {4f59e4bddcb0c06e441adf68a5f252a4e5b4b260} **Short description of error** When the motion blur 'steps' value is set to any value greater than 1 it incorrectly changes the shutter duration and also affects the anti-aliasing quality. From this and the lack of blur on the animated texture strip, it looks like the sampled aspect isn't working. Incorrrect: ![mblur_samples_incorrect_-_a93be410c974_linux_x86-64.png](https://archive.blender.org/developer/F8763641/mblur_samples_incorrect_-_a93be410c974_linux_x86-64.png) Correct: ![mblur_samples_correct_-_c5b6b3d82f56_linux_x86-64.png](https://archive.blender.org/developer/F8763645/mblur_samples_correct_-_c5b6b3d82f56_linux_x86-64.png) **Exact steps for others to reproduce the error** 1. load the attached .blend 2. choose an intermediate frame between 1 and 10 3. set steps value to 1 and render - motion blur duration and AA appear correct 4. set steps value to 4 and render - motion blur duration is reduced by a factor of 4 and AA samples is noticeably worse 5. set steps value to 32 - motion blur is all but gone and AA is poor 6. In earlier builds of 2.90 (eg c5b6b3d82f56) the animated texture line would be correctly blurred [motion_blur_steps_value_v0.2.blend](https://archive.blender.org/developer/F8763660/motion_blur_steps_value_v0.2.blend)

Paul R commented

2020-08-09 20:30:58 +02:00

Added subscriber: @intracube

blender-admin commented

2020-08-09 20:30:58 +02:00

#79646 was marked as duplicate of this issue

RedMser commented

2020-08-10 01:44:27 +02:00

Added subscriber: @RedMser

Clément Foucault commented

2020-08-10 10:03:42 +02:00

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

Jeroen Bakker commented

2020-08-10 11:21:55 +02:00

Added subscriber: @Jeroen-Bakker

Jeroen Bakker commented

2020-08-10 11:21:55 +02:00

It might be that the the the drawing is split into several steps, but only one step is drawn multiple times making the artifacts.

@intracube: Applause for the excellent test file!

Bisecting issue to {4f59e4bddcb0c06e441adf68a5f252a4e5b4b260}

It might be that the the the drawing is split into several steps, but only one step is drawn multiple times making the artifacts. @intracube: Applause for the excellent test file! Bisecting issue to {4f59e4bddcb0c06e441adf68a5f252a4e5b4b260}

Clément Foucault was assigned by Dalai Felinto

2020-08-10 17:02:32 +02:00

blender-admin commented

2020-08-11 19:51:58 +02:00

This issue was referenced by 7219abc5bd

This issue was referenced by 7219abc5bd82048656657b715c4096e7a8756c8f

Clément Foucault commented

2020-08-11 20:07:52 +02:00

Changed status from 'Confirmed' to: 'Resolved'

Clément Foucault closed this issue

2020-08-11 20:07:52 +02:00

Clément Foucault commented

2020-08-12 18:20:20 +02:00

Added subscribers: @moisessalvador, @fclem, @lichtwerk, @Cycles

Paul R commented

2020-08-14 21:25:55 +02:00

Just to confirm that this commit fixes the issue. Thanks!

Thomas Dinges added this to the 2.90 milestone 2023-02-08 16:25:41 +01:00

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Motion blur steps value incorrectly changes shutter duration and affects AA quality #79672