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Author Topic: motion blur  (Read 2693 times)
Description: a good thing?
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claude
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« on: January 10, 2015, 03:29:39 PM »

Is motion blur a good thing or not?  I've been experimenting...

fpsmotion blurshutter speedvideo linkvideo sizeold name
25none0.0https://archive.org/download/mightymandel_2015-01-01/mightymandel_2015-01-01_25fps_0.0blur.mkv108.4MB"interpolated"
25medium0.5https://archive.org/download/mightymandel_2015-01-01/mightymandel_2015-01-01_25fps_0.5blur.mkv96.2MB"motionblur2"
25full1.0https://archive.org/download/mightymandel_2015-01-01/mightymandel_2015-01-01_25fps_1.0blur.mkv93.6MB"motionblur"
60none0.0https://archive.org/download/mightymandel_2015-01-01/mightymandel_2015-01-01_60fps_0.0blur.mkv128.0MB
60medium0.5https://archive.org/download/mightymandel_2015-01-01/mightymandel_2015-01-01_60fps_0.5blur.mkv114.0MB
60full1.0https://archive.org/download/mightymandel_2015-01-01/mightymandel_2015-01-01_60fps_1.0blur.mkv109.4MB
120none0.0https://archive.org/download/mightymandel_2015-01-01/mightymandel_2015-01-01_120fps_0.0blur.mkv148.1MB
120medium0.5https://archive.org/download/mightymandel_2015-01-01/mightymandel_2015-01-01_120fps_0.5blur.mkv137.8MB
120full1.0https://archive.org/download/mightymandel_2015-01-01/mightymandel_2015-01-01_120fps_1.0blur.mkv131.5MB

All videos are the same apart from the frame rate and shutter speed: 1920x512 2m37s.  Motion blur was added during zoom assembly (interpolation between keyframes at 2x zoom levels).  There is no point downloading the 120fps versions unless you have a 120Hz display.

Personally speaking, I prefer the one with medium blur - with no blur there is too much strobing, with full blur there is too much blurring.  Motion blur also makes the videos much more compressible (better quality at lower bitrate).  I got the idea to implement variable shutter speed from reading http://www.shutterangle.com/2012/cinematic-look-frame-rate-shutter-speed/

What are your thoughts?
« Last Edit: January 12, 2015, 01:40:44 PM by claude, Reason: added 120fps versions » Logged
Sockratease
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« Reply #1 on: January 10, 2015, 03:46:09 PM »

Is motion blur a good thing or not?

...

What are your thoughts?

Honestly, and I know I am in the minority on this, I think not.

I don't even like Depth Of Field blurring. Can't stand it in most cases as it obscures details I want to see!

In general I am against all blurring in fractals except in post work to remove noise (often a much faster way to tame things in 3D fractals than adjusting parameters which can bloat render times and often change the look of other areas to remove the noise from unrelated areas)..

So motion blur just makes it harder to enjoy things for me.

But based on it's popularity, I can only assume my views, as usual, are not those of the majority   bubble gum

As for the examples you posted, I think the full blur one is just too much for my detail oriented tastes. The first one is still downloading (things for me are going slow online today), I may post again if I see anything worth mentioning  after viewing it.
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quaz0r
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« Reply #2 on: January 10, 2015, 05:07:48 PM »

i think blur haters are going to be more compelled to comment on this than people who dont know or care one way or the other.   smiley  count me as another blur hater.  though that of course does not include basic image processing like applying a lowpass filter prior to downsampling.  cool video though, the ultra widescreen makes for kind of a cool effect too.
« Last Edit: January 10, 2015, 07:43:10 PM by quaz0r » Logged
youhn
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« Reply #3 on: January 11, 2015, 02:22:01 AM »

I do like blur, but only on levels that are hardly visible. Think 60fps VS 30fps. For video I would like motion blur for the in-between frames. This means rendering a 30 fps video at 60 or more fps, and then combine 2 or more frames into 1 static frame. This emulates the motion blur due to the shutter time of discrete real-world video/film capture devices.
* youhn now looking at the vids

The medium motion blurred movie is still too much blur. This could be due to the high zoom speed. I do prefer this slightly blurred version over the interpolated movie, for it's more fluent motion. If you would record the video at 60 fps with no blur (of very little blur), I think I would be happy aswell. Motion blur and noise in general can be used to give the impression of more detail. Think of what dimming the light does to our imagination and vision. There is actually less detail, but our brain fills in the blanks.
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3dickulus
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« Reply #4 on: January 11, 2015, 05:19:09 AM »

I like motion blur #2 smiley
when pushed beyond what might naturally occur from shutter speed it can make an interesting effect too, all though I could just remove my glasses wink so I have to agree with Sockratease in some respects.

I have achieved good results by not clearing the frame buffer and writing GL pixels with n% alpha where n% determines how many frames the 'trail' persists.
here is a small short motion blur video, using this technique required no additional calculating because the effect is entirely a result of how the pixels are being written to the buffer.
The proggie runs at 50+ fps, the video recording is live from my desktop at 30 fps.
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claude
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« Reply #5 on: January 11, 2015, 11:55:45 AM »

I do like blur, but only on levels that are hardly visible. Think 60fps VS 30fps. For video I would like motion blur for the in-between frames. This means rendering a 30 fps video at 60 or more fps, and then combine 2 or more frames into 1 static frame. This emulates the motion blur due to the shutter time of discrete real-world video/film capture devices.

Yes that's how I implemented motion blur in my zoom assembler.  It calculates the required number of subframes for smooth appearance (ie, each subframe moves the image by at most 1 pixel):
https://gitorious.org/maximus/mightymandel/commit/970f411c393b9d471d8b94019e077acf36dafea4
http://code.mathr.co.uk/mightymandel/commitdiff/970f411c393b9d471d8b94019e077acf36dafea4
Then it uses a fraction of those for variable shutter speed:
https://gitorious.org/maximus/mightymandel/commit/dd119b3545674897fa2a9f59a9c0b67b5fda56b3
http://code.mathr.co.uk/mightymandel/commitdiff/dd119b3545674897fa2a9f59a9c0b67b5fda56b3

I might render and upload 60fps versions later today, for further comparison.

here is a small short motion blur video, using this technique required no additional calculating because the effect is entirely a result of how the pixels are being written to the buffer.

I give all the subframes within a frame equal weighting, which I guess emulates a physical shutter more closely.  I did experiment with your method, but the tiny alpha% required for smooth appearance for the fast zoom speed I used led to quantisation problems with the 8bit framebuffer.

Attached is a still from your video - seems the rendering framerate wasn't high enough to blur smoothly the fast motion on the left, so there is a staggered effect (which probably has a technical name, I just don't know it).  Calculating required subframes (aka rendering framerate multiplier) for zoom is easy because motion is always greatest at the corners, and with a fixed zoom speed it's even easier.


* kuni-4.jpg (96.47 KB, 480x300 - viewed 638 times.)
« Last Edit: March 10, 2015, 02:32:20 AM by claude, Reason: gitorious.org is closing » Logged
claude
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« Reply #6 on: January 11, 2015, 03:10:48 PM »

I might render and upload 60fps versions later today, for further comparison.

Added 60fps versions and renamed the 25fps versions for consistency.  Updated the table in the first post.
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youhn
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« Reply #7 on: January 11, 2015, 04:23:31 PM »

Thought I would like the non-motion-blurred 60 fps version, but I actually prefer the 0.5 blurred 60 fps version. A side-effect I notice is that with this constant zooming into the center, the tangential lines seem to disappear into the white background while they gain speed towards the edges of the screen. I think this automatically puts focus on the radial shapes, the ones that are more easily picked up by our brain. So this motion blurring increases the focus contrast of our perception, or something like that. Not sure what words to use for describing this kind of contrast.

This implementation of the motion blur worked out very well.

Maybe I'll do a re-render of <a href="https://www.youtube.com/v/brrgOmuVL5c&rel=1&fs=1&hd=1" target="_blank">https://www.youtube.com/v/brrgOmuVL5c&rel=1&fs=1&hd=1</a>, when all needed features happened to be combined into one specific fractal program. Though it will be deeper, just because we can.
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Adam Majewski
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« Reply #8 on: January 11, 2015, 04:35:18 PM »

fpsmotion blurshutter speedvideo linkvideo sizeold name
25none0.0https://archive.org/download/mightymandel_2015-01-01/mightymandel_2015-01-01_25fps_0.0blur.mkv138.3MB"interpolated"
60none0.0https://archive.org/download/mightymandel_2015-01-01/mightymandel_2015-01-01_60fps_0.0blur.mkv128.0MB


Why 60 fps video is smaller then 25 fps video ( when  the same motion blur and shutter speed are the same ) ?
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claude
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« Reply #9 on: January 11, 2015, 04:41:53 PM »

Why 60 fps video is smaller then 25 fps video ( when  the same motion blur and shutter speed are the same ) ?

Probably because neighbouring frames are more similar (less zoom between them), which means the video codec can compress it better (motion estimation is likely to work better, etc).

It was encoded with different avconv settings (oops...).  Re-encoded with the same settings as the others, the comparable size is: 109MB

Fixed version uploaded and table updated.
« Last Edit: January 11, 2015, 05:39:22 PM by claude » Logged
Adam Majewski
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« Reply #10 on: January 11, 2015, 05:48:41 PM »

I do not know the theory but visually 25 fps without blur is the best for me



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claude
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« Reply #11 on: January 12, 2015, 01:42:59 PM »

Updated first post with 120fps versions for those with 120Hz displays.  I only have a 59.94Hz display, so I can't judge them.
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3dickulus
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« Reply #12 on: January 13, 2015, 04:02:48 AM »

persistence of vision plays a big role

when paused at a frame that has black lines on a white background it looks as it should but when strung together with the line moving a large distance I perceive strobe trail, not because it's there, but because it was there. so I think that in the case of large movements or too fast zooms, no amount of motion blur will prevent that residual image from registering in our brains, the only answer is more frames as in 120Hz or up to a value that makes the motion from frame to frame minimized to some % of the width of a given feature
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billtavis
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« Reply #13 on: March 20, 2015, 01:28:22 AM »

I preferred the full blur myself. The video with full blur was so buttery smooth flying in... I don't think zoom videos should always be about seeing every little detail, it's more about the journey so I prefer a smoother ride.

One way to get some flexibility with motion blur is to render two passes. That is, for every frame you would render one image which is the fractal with no blur applied and a second image which records the velocity. This is usually done by storing the x-velocity in the red channel and the y-velocity in the green channel. That way, the motion blur can be applied as a post-production step and tweaked as needed. This is often times (but not always) very close to the quality of sub-frame sampling, but with more flexibility and less time.

Of course, for a straight-in zoom all that is needed is a simple radial blur.
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