How do you make motion blur in animations as fast as possible?

I have studied that problem a little and here's what I've come up with.

Well, there's two ways to make motion blur.

The internal method is to use MegaPOV's motion blur.
The external method is to use a program to average the frames outputted by
POV-Ray.

What is more efficient (faster)?

If you want to use realistic motion blur, the internal method is always
faster. For realistic motion blur the motion blur clock_delta is never
bigger than POV-Ray's clock_delta.

It's a good idea to use this set-up:

global_settings { motion_blur SAMPLES, clock_delta*(1-1/SAMPLES) }

However, sometimes instead of using realistic motion blur, you want to
exaggerate the effect. In that case, what is faster?

If you want to use exaggerated motion blur it's fastest to use a combination
of internal and external motion blur.

For the internal motion blur, use the same set-up I've described for
realistic motion blur. (You don't need to use a higher frame-rate than you
would have used without motion blur.)
Then, after the animation is rendered, you can exaggerate the blur effect by
using the external motion blur method. If you use the set-up I've described,
the trails of motion blur from the different frames will match up
seamlessly.

The only limitation of this method is that you can only exaggerate the
effect by a multiple of the clock_delta. (You can only make the blur twice
as strong, 3 times as strong, 4 times as strong etc., but not 1.6 times as
strong.) But that isn't really a big problem I think...

Hope you find this useful!

Greetings,

Rune
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> global_settings { motion_blur SAMPLES, clock_delta*(1-1/SAMPLES) }

Doesn't work for me... MegaPOV just stops. If I use 1 instead of
clock_delta*... it's happy.

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Rune <run### [at] inamecom> wrote:
: What is more efficient (faster)?

  I think that internal motion blur is always faster unless all the scene
is moving. This is because only part of the image has to be extra-calculated
instead of the whole image (as happens when using the external method).
  If all the scene is moving, then both methods may be as slow.

-- 
main(i,_){for(_?--i,main(i+2,"FhhQHFIJD|FQTITFN]zRFHhhTBFHhhTBFysdB"[i]
):_;i&&_>1;printf("%s",_-70?_&1?"[]":" ":(_=0,"\n")),_/=2);} /*- Warp -*/

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In article <39edbc6b@news.povray.org>, "Tony[B]" 
<ben### [at] panamac-comnet> wrote:

> Doesn't work for me... MegaPOV just stops. If I use 1 instead of
> clock_delta*... it's happy.

Sounds like a bug...what version are you using? The latest is 0.6a.
Have you tried something like this?

#declare Delta = clock_delta*(1-1/SAMPLES);
global_settings {motion_blur SAMPLES, Delta}

or this?
#declare Delta = clock_delta;
global_settings {motion_blur SAMPLES, Delta*(1-1/SAMPLES)}

-- 
Christopher James Huff
Personal: chr### [at] maccom, http://homepage.mac.com/chrishuff/
TAG: chr### [at] tagpovrayorg, http://tag.povray.org/

<><

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"Tony[B]" wrote:
> > global_settings { motion_blur SAMPLES, clock_delta*(1-1/SAMPLES) }
>
> Doesn't work for me... MegaPOV just stops.

Did you turn on animation? The method works only for animations.

> If I use 1 instead of clock_delta*... it's happy.

But that's not efficient! :-o

Greetings,

Rune
--
\ Include files, tutorials, 3D images, raytracing jokes,
/ The POV Desktop Theme, and The POV-Ray Logo Contest can
\ all be found at http://rsj.mobilixnet.dk (updated October 9)
/ Also visit http://www.povrayusers.org

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"Warp" wrote:
>   I think that internal motion blur is always faster

When you do exaggerated motion blur completely internally, some motion blur
samples in one frame are identical to some samples in the next frame. Doing
the same samples twice or more is a waste of time. To optimise speed, the
unique samples should be done internally, and the "overlapping" samples
should be done externally.

Rune
--
\ Include files, tutorials, 3D images, raytracing jokes,
/ The POV Desktop Theme, and The POV-Ray Logo Contest can
\ all be found at http://rsj.mobilixnet.dk (updated October 9)
/ Also visit http://www.povrayusers.org

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In article <39ee17b3@news.povray.org>, "Rune" <run### [at] inamecom> 
wrote:

> When you do exaggerated motion blur completely internally, some 
> motion blur samples in one frame are identical to some samples in the 
> next frame. Doing the same samples twice or more is a waste of time. 
> To optimise speed, the unique samples should be done internally, and 
> the "overlapping" samples should be done externally.

If you have an animation, that is. You can use motion blur to do the 
supersampling, and frame averaging to exaggerate the blur. If you are 
doing a still, frame averaging combined with motion blur would be less 
efficient, since you have to recalculate things that don't change.

-- 
Christopher James Huff
Personal: chr### [at] maccom, http://homepage.mac.com/chrishuff/
TAG: chr### [at] tagpovrayorg, http://tag.povray.org/

<><

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"Chris Huff" wrote:
> If you have an animation, that is.

Quote from my original message:
"How do you make motion blur in animations as fast as possible?"
                             ^^^^^^^^^^^^^

> You can use motion blur to do the supersampling, and frame
> averaging to exaggerate the blur.

Yes, exactly.

> If you are doing a still, frame averaging combined with
> motion blur would be less efficient, since you have to
> recalculate things that don't change.

I was never talking about stills.

But since a still image can be considered an animation with only one frame,
my method still applies. (Averaging one frame is of no use, so use internal
motion blur only.)

Greetings,

Rune
--
\ Include files, tutorials, 3D images, raytracing jokes,
/ The POV Desktop Theme, and The POV-Ray Logo Contest can
\ all be found at http://rsj.mobilixnet.dk (updated October 9)
/ Also visit http://www.povrayusers.org

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> Sounds like a bug...what version are you using? The latest is 0.6a.

I pride myself on always having the latest versions of everything. :)

> Have you tried something like this?

Nope. I just copied and pasted it from what Rune showed.

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Rune wrote:
> 
> How do you make motion blur in animations as fast as possible?
> 
> Well, there's two ways to make motion blur.
> 
> The internal method is to use MegaPOV's motion blur.
> The external method is to use a program to average the frames
> outputted by POV-Ray.

Hey!  I used POV-Ray to average the frames output by POV-Ray.
Does that count as a third method?

Regards,
John
-- 
ICQ: 46085459

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