Cycles Motion Blur is broken #39840

New Issue

Maverick · 2014-04-22T13:36:27+02:00

Maverick commented

2014-04-22 13:36:27 +02:00

System Information
win64 i7 gtx titan

Blender Version
blender-2.70-b179647-win64

Short description of error
Multiple issues here both with Cycles and Internal. Cycles is more severe though.

Cycles:
1.Mblur fails for simple scaling
2.Mblur looks washed for last frame of the animation.
For example if you render the frame #6 you won't see any mblur even for a shutter time of 4.0

Blender Internal
1.Sampled motion blur fails for the last frame. Internal seems to sample only after the active frame instead of before and after.

Exact steps for others to reproduce the error
Check attached files.

Thank you

mblur_bug.blend

**System Information** win64 i7 gtx titan **Blender Version** blender-2.70-b179647-win64 **Short description of error** Multiple issues here both with Cycles and Internal. Cycles is more severe though. Cycles: 1.Mblur fails for simple scaling 2.Mblur looks washed for last frame of the animation. For example if you render the frame #6 you won't see any mblur even for a shutter time of 4.0 Blender Internal 1.Sampled motion blur fails for the last frame. Internal seems to sample only after the active frame instead of before and after. **Exact steps for others to reproduce the error** Check attached files. Thank you ![mblurbug.png](https://archive.blender.org/developer/F85626/mblurbug.png) [mblur_bug.blend](https://archive.blender.org/developer/F85628/mblur_bug.blend)

Maverick commented

2014-04-22 13:36:27 +02:00

Changed status to: 'Open'

Maverick commented

2014-04-22 13:36:27 +02:00

Added subscriber: @dragostanasie

Joel Godin commented

2014-04-22 16:27:04 +02:00

Added subscriber: @joel.godin

Joel Godin commented

2014-04-22 16:27:04 +02:00

I think it is still not enabled.
"Currently scale motion is not supported, only object transformations like translation and rotation. "
http://wiki.blender.org/index.php/Doc:2.6/Manual/Render/Cycles/Integrator

I think it is still not enabled. "Currently scale motion is not supported, only object transformations like translation and rotation. " http://wiki.blender.org/index.php/Doc:2.6/Manual/Render/Cycles/Integrator

Brecht Van Lommel commented

2014-04-22 16:28:01 +02:00

Changed status from 'Open' to: 'Archived'

Brecht Van Lommel closed this issue

2014-04-22 16:28:01 +02:00

Brecht Van Lommel self-assigned this 2014-04-22 16:28:01 +02:00

Brecht Van Lommel commented

2014-04-22 16:28:01 +02:00

Cycles does not currently support scale motion as mentioned here:
http://wiki.blender.org/index.php/Doc:2.6/Manual/Render/Cycles/Integrator#Motion_Blur

Further object motion only supports taking three samples, one at a earlier frame, current frame and later frame. For fast motion and/or long shutter time this indeed not great, but it's again a documented limitation, the steps option is only for deformation motion blur.
http://wiki.blender.org/index.php/Dev:Ref/Release_Notes/2.71/Cycles

Blender Internal for some reason has always taken the shutter time after the current frame, rather than centering it around the current frame. That's easily changed with a patch like this, but it would break backwards compatibility to change this so I won't.

diff --git a/source/blender/render/intern/source/pipeline.c b/source/blender/render/intern/source/pipeline.c
index 1a3d07f..61a1c48 100644

  - a/source/blender/render/intern/source/pipeline.c

+++ b/source/blender/render/intern/source/pipeline.c
@@ -1334,6 +1334,7 @@ static void do_render_blur_3d(Render *re)
        /* do the blur steps */
        while (blur--) {
                re->mblur_offs = re->r.blurfac * ((float)(re->r.mblur_samples - blur)) / (float)re->r.mblur_samples;
+               re->mblur_offs -= 0.5f * re->r.blurfac;

                re->i.curblur = re->r.mblur_samples - blur;    /* stats */

Cycles does not currently support scale motion as mentioned here: http://wiki.blender.org/index.php/Doc:2.6/Manual/Render/Cycles/Integrator#Motion_Blur Further object motion only supports taking three samples, one at a earlier frame, current frame and later frame. For fast motion and/or long shutter time this indeed not great, but it's again a documented limitation, the steps option is only for deformation motion blur. http://wiki.blender.org/index.php/Dev:Ref/Release_Notes/2.71/Cycles Blender Internal for some reason has always taken the shutter time after the current frame, rather than centering it around the current frame. That's easily changed with a patch like this, but it would break backwards compatibility to change this so I won't. ``` diff --git a/source/blender/render/intern/source/pipeline.c b/source/blender/render/intern/source/pipeline.c index 1a3d07f..61a1c48 100644 ``` - a/source/blender/render/intern/source/pipeline.c ``` +++ b/source/blender/render/intern/source/pipeline.c @@ -1334,6 +1334,7 @@ static void do_render_blur_3d(Render *re) /* do the blur steps */ while (blur--) { re->mblur_offs = re->r.blurfac * ((float)(re->r.mblur_samples - blur)) / (float)re->r.mblur_samples; + re->mblur_offs -= 0.5f * re->r.blurfac; re->i.curblur = re->r.mblur_samples - blur; /* stats */

Maverick commented

2014-04-22 16:43:49 +02:00

Thanks for clearing this up brecht.

Will motion blur be improved to allow fast motion by sampling fractional frames or more frame ahead and before ?
This is needed for things like insect wings, hands, fingers, and other character interactions with objects.

About the internal, maybe sampling before and ahead could be added as an option without the need to break backwards compatibility if it's not too much trouble.

Thank you.

Thanks for clearing this up brecht. Will motion blur be improved to allow fast motion by sampling fractional frames or more frame ahead and before ? This is needed for things like insect wings, hands, fingers, and other character interactions with objects. About the internal, maybe sampling before and ahead could be added as an option without the need to break backwards compatibility if it's not too much trouble. Thank you.

Brecht Van Lommel commented

2014-04-22 23:51:11 +02:00

The Cycles issue will be solved at some point, not sure yet when.

For Blender Internal, I've added it to the To Do list. There's no maintainer for that anymore so not sure if/when that will be fixed.
http://wiki.blender.org/index.php/Dev:2.5/Source/Development/Todo/Render

The Cycles issue will be solved at some point, not sure yet when. For Blender Internal, I've added it to the To Do list. There's no maintainer for that anymore so not sure if/when that will be fixed. http://wiki.blender.org/index.php/Dev:2.5/Source/Development/Todo/Render

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Cycles Motion Blur is broken #39840