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Rendering every nth frame

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Ailbhe CantwellRendering every nth frame
by on Sep 7, 2016 at 9:55:11 am

Hi there

I'm looking to give a traditional animation look to an AE rigged character animation. It's a 25 fps comp, and I'm looking for an expression to render every 2nd frame, but keep the length of the comp the same. So drop every second frame and play every frame that's kept for twice as long, I guess. If I choose to render 12 fps in the render settings it also applies that to the camera move, which makes it juddery.

I had a Dan Ebberts expression years back that did this, but cannot find it now.

Any help would be greatly appreciated! ;)


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Walter SoykaRe: Rendering every nth frame
by on Sep 7, 2016 at 1:24:55 pm

You can use this expression:

posterizeTime(1/thisComp.frameDuration/2);
value;


Walter Soyka
Designer & Mad Scientist at Keen Live [link]
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
@keenlive [twitter]   |   RenderBreak [blog]   |   Profile [LinkedIn]


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Roei TzorefRe: Rendering every nth frame
by on Sep 7, 2016 at 2:31:07 pm

Great information Walter. what I used to do when I wanted camera moves in my stop motion was to separate the comps. the main comp at 25fps will be the camera move, and inside was the 12 fps comp with the "preserve frame rate when nested" checked. now it looks to me this expression gives you to work with 2 different frame rates at the same comp, correct?


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Roei TzorefRe: Rendering every nth frame
by on Sep 7, 2016 at 2:49:51 pm

BTW can it work the other way around? I have a multi layered composition with rigging and many layers that is in a 12fps Composition. I want just the camera to move at 25 fps. my assumption is that in this situation there's no way around that and I have to use a master comp at 25fps with the camera move, and 12 fps with preserve frame. maybe this useful expression does not suit me after all because when I animate in stop motion I work in 12 fps (same as my camera recording).


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Walter SoykaRe: Rendering every nth frame
by on Sep 7, 2016 at 3:44:01 pm

[Roei Tzoref] "BTW can it work the other way around? I have a multi layered composition with rigging and many layers that is in a 12fps Composition. I want just the camera to move at 25 fps. my assumption is that in this situation there's no way around that and I have to use a master comp at 25fps with the camera move, and 12 fps with preserve frame. maybe this useful expression does not suit me after all because when I animate in stop motion I work in 12 fps (same as my camera recording)."

Although you can force the expression to evaluate at a higher rate (25fps) than the frame rate (12fps), it will do you no good; Ae will render at the comp's frame rate (12fps).

Walter Soyka
Designer & Mad Scientist at Keen Live [link]
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
@keenlive [twitter]   |   RenderBreak [blog]   |   Profile [LinkedIn]


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Dave LaRondeRe: Rendering every nth frame
by on Sep 7, 2016 at 4:06:18 pm

Is there a good reason NOT to use the Posterize Time effect instead of an expression?

Dave LaRonde
Promotion Producer
KGAN (CBS) & KFXA (Fox) Cedar Rapids, IA


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Roei TzorefRe: Rendering every nth frame
by on Sep 7, 2016 at 4:12:31 pm

[Dave LaRonde] "Is there a good reason NOT to use the Posterize Time effect instead of an expression?
"


effects render before transformations so if I have a movement set by transform keyframe, the PT effect won't affect it. this expression applies to the value itself.


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Walter SoykaRe: Rendering every nth frame
by on Sep 7, 2016 at 4:17:31 pm

[Dave LaRonde] "Is there a good reason NOT to use the Posterize Time effect instead of an expression?"

Yes. Using an effect won't work. Effects are rendered BEFORE transforms, so the Posterize Time effect would let you set the frame rate for the footage, but not any position/scale/rotation animation you create. You'd still get smoothly interpolated motion instead of stuttery cartoon motion.

Walter Soyka
Designer & Mad Scientist at Keen Live [link]
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
@keenlive [twitter]   |   RenderBreak [blog]   |   Profile [LinkedIn]


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Dave LaRondeRe: Rendering every nth frame
by on Sep 7, 2016 at 5:17:44 pm

....but not if Posterize Time were applied to a nested comp of the animation, which would sort out the render order.

Dave LaRonde
Promotion Producer
KGAN (CBS) & KFXA (Fox) Cedar Rapids, IA


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Walter SoykaRe: Rendering every nth frame
by on Sep 7, 2016 at 5:48:08 pm

[Dave LaRonde] "....but not if Posterize Time were applied to a nested comp of the animation, which would sort out the render order."

Yes, but then you have to navigate through piles of precomps to tweak the keyframing. With the expression applied, you can keep all the keyframing live and in the same comp for easy editing.

Walter Soyka
Designer & Mad Scientist at Keen Live [link]
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
@keenlive [twitter]   |   RenderBreak [blog]   |   Profile [LinkedIn]


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Walter SoykaRe: Rendering every nth frame
by on Sep 7, 2016 at 3:42:06 pm

[Roei Tzoref] " now it looks to me this expression gives you to work with 2 different frame rates at the same comp, correct?"

Effectively, yes. posterizeTime() allows you to dictate how often a given property is evaluated. You can apply different rates to different properties.

Walter Soyka
Designer & Mad Scientist at Keen Live [link]
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
@keenlive [twitter]   |   RenderBreak [blog]   |   Profile [LinkedIn]


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Roei TzorefRe: Rendering every nth frame
by on Sep 7, 2016 at 3:43:29 pm

thank you. I guess I thought this one is only good for TR property and therefor requires pre-comping for keyframe animation


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