Sqaush and stretch time, Is there a workflow?

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  04 April 2014
Sqaush and stretch time, Is there a workflow?

I've tried 'oflow' and 'kronos', they give really awful result after a keyframe is set to reduce the timing speed.
Is there a workaround or a plugin to play with timing?
 
  04 April 2014
It really depends what your trying to do. If you want basic re-timing without the optical flow which kronos & oflow use then I would look at the retime or timewarp nodes. They only do basic frame blending.
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-deke
 
  04 April 2014
Basically I use oflow & kronos to have different result and play with the settings, but its not going to work on the whole image, you have to separate fg/md/bg areas and find something which work for each area. If its not working or you have to much motion blur, you have to restore manually. Strong retimes are very painful!
 
  04 April 2014
retiming is a massive subject, there's simply no solution that will work in every case. It absolutely depends on the footage in question. Some retimes can be a one-click-solution, and if you get a few of those in your time then great - but most of the time there's a load of cleanup and comp work left to do when retiming a shot that doesn't naturally lend it's self to an easy retime.

if you are completely stuck, let us see the footage you are working on and we'll go from there, but unfortunately, like most things in VFX there's no real answer.
 
  04 April 2014
Quote: Originally posted by RickBovill
if you are completely stuck, let us see the footage you are working on and we'll go from there


Using the 'oflow' node. The problem arises when i set a keyframe for the speed attribute to reduce the playback speed from 1.0 to .05, the footage acts really funny after the keyframes are set, though in the curves editor the curves look really simple & fine.
I've up loaded the project files, (using nuke8)

the files on Gdrive
 
  04 April 2014
thats a really hard retime, going down to 5% of original speed means you need a lot of new frames calculated and this will lead to a lot of artifacts
 
  04 April 2014
Originally Posted by Daff: Using the 'oflow' node. The problem arises when i set a keyframe for the speed attribute to reduce the playback speed from 1.0 to .05, the footage acts really funny after the keyframes are set, though in the curves editor the curves look really simple & fine.
I've up loaded the project files, (using nuke8)

the files on Gdrive


oof!

Thanks for posting the video, without even trying it in nuke myself I can tell you you have almost no chance of retiming that to .1 speed. the retime works by optical flow, which looks at where and how fast pixels are moving int he image. It's obvious to us [humans] the bike is spinning, so just slow it down right? well, all of those reflections that are dancing around the bike look like fast moving pixels to nuke, and they are moving in a different direction to the bike. reflections, transparency and such a large, relativly fast moving 3D mass are all the things that make this not just hard, but just not even worth trying.

if the bike render is yours - render it again. slower ! or if you have motion vectors you could try using them with kronos and that will take pixel motion judgement out of the equation but still won't really work (and i've never tried that with kronos to be fair, I just know it has an input for vectors)

sorry! back to 3D!
 
  04 April 2014
aaarrhh

The scene's really expensive, arnold scene. So i could only render 120 frames, which took a day.
Thanks alot!
So how do you guys think approaching this professionally would be, would the correct way of handling this be with nuke, or other app like AE?
 
  04 April 2014
doesnt matter which app you use: the retime function in AE is basically Kronos from nuke
and in all other apps optical flow retime is based on the same principles, so there will be the same problems

such extreme retimes are always problematic.
if you go down to 5% of the original speed, this means you make out of 1 frame 20 new frames. there is no way of doing that without artifacts.

i see no other way then to rerender this scene and then try a less extreme retime
 
  04 April 2014
Originally Posted by Daff: aaarrhh

The scene's really expensive, arnold scene. So i could only render 120 frames, which took a day.
Thanks alot!
So how do you guys think approaching this professionally would be, would the correct way of handling this be with nuke, or other app like AE?


This answer may be a little more literal than you were expecting, but if I had to do a shot of a motorbike on a turntable which started at one speed and ramped down to another speed I'd do that in the render; it;s just a turntable afterall. I would not even consider re timing such a shiny complex object in post.

If the scene is too heavy to render then maybe adjust and test your render settings further. there seems to be some artifacts in your render which looks like you have two pieces of the same geometry in the same place (the lower fairing panel ? shows this as a weird checkerboard pattern on the surface) so I think there's still scope in the render stage of your project to get a different result. If it's just for a personal project or a student reel I'd be tempted to render it at lower res' at the correct speed, rather than try to retime it. you're honestly not going to be able to re-time that shot without a load of work. As PingKing says - @5% 19 out of 20 frames are made-up / estimated based on the few frames that it does have. there's literally no other plugin or magic that will work here - the professional solution would be to re-render your shot.

not the answer you may have been wanting!
 
  04 April 2014
Thumbs up

Thanks guys, i think i'll have to face my fear, re-render the work again.

Quote: there seems to be some artifacts in your render which looks like you have two pieces of the same geometry in the same place (the lower fairing panel ? shows this as a weird checkerboard pattern on the surface)

I realised that when i took a look at the objectID channel, i forgot to hide older geometry after duplicating, more reasons to re-render i guess.
 
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