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Activating contiuous rasterization of a pre-comp makes position and scale go awry

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James Martin
Activating contiuous rasterization of a pre-comp makes position and scale go awry
on Oct 27, 2014 at 6:28:47 pm
Last Edited By James Martin on Oct 27, 2014 at 6:30:32 pm

If anyone can explain what's going on with this, and suggest a fix, I owe you one.

The Problem (this is part of a more complicated comp, but I've stripped out everything apart from the offending element for clarity):

I created a wiggly line by drawing an open mask on a shape layer and generating a stroke effect along the path.

I duped this shape layer, changed the color of the stroke, and key-framed the start/end positions of the stroke to make a pulse race along it. The pulse is repeated several times, and gets faster.

I then pre-comped all of this. The precomp was then pick-whipped to a null layer whose scale and position were animated. As the scale starts at greater than 100% I turned on continuous rasterisation of the pre-comp.

This elicited a weird result: the wiggle changed scale and position, but the pulses do not follow, despite being in the same pre-comp. If I turn off continuous rasterization, the wiggle and the pulse stay together.

Why?

The only thing that is different about the wiggle and pulse is animation of the start/end of the stroke.

I know moving the scale-position null in to within the pre-comp would fix the problem, but it isn't a workable solution in my project.

I've put the stripped down project (no external files to link to) and an example clip of the problem on WeTransfer (v small file sizes). It might help to understand what I'm explaining:
http://we.tl/Sp288phlKM

Here's the clip:

Raster Weirdness



Thanks,

Jame


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Dave LaRonde
Re: Activating contiuous rasterization of a pre-comp makes position and scale go awry
on Oct 27, 2014 at 8:03:25 pm

Prerender the wiggly animation and use the resulting file as a 3D layer.

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


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James Martin
Re: Activating contiuous rasterization of a pre-comp makes position and scale go awry
on Oct 27, 2014 at 8:37:33 pm

Thanks Dave. That's a good workaround.

Any idea why that weirdness is happening?


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Dave LaRonde
Re: Activating contiuous rasterization of a pre-comp makes position and scale go awry
on Oct 27, 2014 at 9:50:47 pm

Well, it might have something to do with the fact that Stroke doesn't respond to continuous rasterization: it's a bitmapped effect.

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


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James Martin
Re: Activating contiuous rasterization of a pre-comp makes position and scale go awry
on Oct 28, 2014 at 9:20:04 am

Yup, that would make sense. I just can't figure out why the animated stroke would lose all S&P data between comps while the static one doesn't.

I might have to chalk it off to experience and move on.


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Dave LaRonde
Re: Activating contiuous rasterization of a pre-comp makes position and scale go awry
on Oct 28, 2014 at 4:00:33 pm

Prerendering is an often-overlooked option. You may lose the ability to change your mind easily, but you gain simplicity.

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


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Walter Soyka
Re: Activating contiuous rasterization of a pre-comp makes position and scale go awry
on Oct 29, 2014 at 6:35:02 pm

[James Martin] "Yup, that would make sense. I just can't figure out why the animated stroke would lose all S&P data between comps while the static one doesn't."

The switch is not "continuous rasterization" for precomps. It's "collapse transformations." Even though the net result for both is often retaining sharpness, they work completely differently.

"Continuously rasterize" tells Ae to reinterpret the vector art's curve data at each new size as its scale or position changes, instead of intrepreting or rasterizing the data once and then operating on the raster.

Collapse transformations mathematically combines the transformations on the precomp layer in the main comp with the transformations on the layers inside the precomp into a single operation.

By way of example: with collapse transformations on, if you scale a layer down by half inside the precomp, then double the precomp in the main comp, Ae will concatenate or "collapse" the transformations. 50% * 200% = 100%, or no change.

If you turn off collapse transformations, Ae will first scale the layer down to 50% and rasterize it at that size, then scale that up 200%. The final size will be the same, but you will lose sharpness because you have thrown away so much data in the first scale-down transformation.

As Dave notes, your animated stroke effect is changing position because of the way Ae deals with shape layers (vectors) and effects (rasters).

I think your best solution is not to use the Stroke effect, forcing Ae to rasterize the shape layer before processing, but rather to use the Trim Paths feature on your shape layer to accomplish the same result without premature rasterization.

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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