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Animate shape along another shapes path

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Declan Smith
Animate shape along another shapes path
on Mar 3, 2012 at 8:51:20 pm

I have a shape layer with a rectangle that has animated dashes (such that they march around the stroke of the rectangle). What I would like to do is put an arrow (or other shape) on that path to follow the path of the stroke for example.

Is there anyway to extract the path data from a standard shape on a shape layer, such as rounded rectangle or ellipse etc , i.e. shape > mask ? Custom shapes are no problem, I can get the path data from these, only the preset shapes are causing me difficulty.

Declan Smith
http://www.madpanic.tv
After Effects CS5.5/ FCS3 / Canon 7D / Canon XL2 / Reason / Cubase

"it's either binary or it's not"


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Erik Waluska
Re: Animate shape along another shapes path
on Mar 3, 2012 at 11:23:52 pm

Here's a script that will convert the shape layer to a mask.

http://www.redefinery.com/ae/view.php?item=rd_ShapesToMasks


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Declan Smith
Re: Animate shape along another shapes path
on Mar 3, 2012 at 11:28:24 pm

Thanks. I tried that, but it doesn't seem to play ball with the rectangles, ellipses, polygons or stars. Maybe they are treated differently? The script works well for custom paths though.

Declan Smith
http://www.madpanic.tv
After Effects CS5.5/ FCS3 / Canon 7D / Canon XL2 / Reason / Cubase

"it's either binary or it's not"


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Erik Waluska
Re: Animate shape along another shapes path
on Mar 4, 2012 at 2:44:21 am

Maybe you could auto-trace the shape layer? Not sure if that would work for what you are doing but worth a try.


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Todd Kopriva
Re: Animate shape along another shapes path
on Mar 4, 2012 at 6:19:31 am

The distinction that matters here is that between path-based shapes and parametric shapes. By default, the shape tools create parametric shapes, but you can make them create path-based shapes by holding Alt (or Option) when first using the tool to cretae the shape.

More information here:

http://help.adobe.com/en_US/aftereffects/cs/using/WS49C4F119-DE6F-48c3-B5B6...

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Todd Kopriva, Adobe Systems Incorporated
Technical Support for professional video software
After Effects Help & Support
Premiere Pro Help & Support
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Declan Smith
Re: Animate shape along another shapes path
on Mar 4, 2012 at 9:17:45 am

Didn't know about the Option Drag feature, very useful, thankyoul

I suppose the example I gave with a simple rectangle too simplistic. What I am trying to do is have an arrow head follow the same animated path that dashes on the stroke follow. My assumption here was that stroke follows the path. If you have a complicated shape made up of multiple shapes with merged paths, pucker&bloat or other operators, it would be nice to have someway of tracking the resultant (and possible keyframed) path.

I've tried autotrace, but that results in hundreds of small masks, each of which is closed around the pixels it's defining (like multiple tiny polygons), so copy and pasting the path doesn't give the desired results as the arrowhead will traverse each mask shape.

Declan Smith
http://www.madpanic.tv
After Effects CS5.5/ FCS3 / Canon 7D / Canon XL2 / Reason / Cubase

"it's either binary or it's not"


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Roland R. Kahlenberg
Re: Animate shape along another shapes path
on Mar 5, 2012 at 1:51:11 am

For complex stuff, it's best to use the Text Tool. The 'issue' with the Shape Tool is that the paths determine both the shape as well as the motion path.

HTH
RoRK

Intensive AE & Mocha Training in Singapore and Malaysia
Adobe ACE/ACI (version 7) & Imagineer Systems Inc Approved Mocha Trainer


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Todd Kopriva
Re: Animate shape along another shapes path
on Dec 14, 2013 at 6:54:26 pm

The After Effects CC (12.2) update makes creating a Bezier path for a shape easier and more discoverable, as well as adding the ability to convert from parametric paths to Bezier paths.

option for creating shape layers based on Bezier paths:

When a shape tool (Rectangle, Rounded Rectangle, Polygon, Star, or Ellipse tool) is active, you can use the new Bezier Path option in the Tools panel to create a new shape based on a Bezier path, as opposed to the default of creating a new shape based on a parametric path. Holding the Alt (Windows) or Option (Mac OS) key while drawing a shape causes the opposite behavior—i.e., if the Bezier Path option is enabled, holding the Alt or Option key causes the shape tool to create a parametric path; if the Bezier Path option is disabled, holding the Alt or Option key causes the shape tool to create a Bezier path.

command for converting a parametric shape layer path to a Bezier path:

You can convert a parametric path to a Bezier path after the parametric path has already been created by context-clicking (right-clicking or Control-clicking on Mac OS) the property group for the parametric path (e.g., Rectangle Path 1) and choosing the Convert To Bezier Path command from the context menu. If the parametric path is animated (keyframed), the converted Bezier path is a static path based on the parametric path at the current time; keyframes are lost.

IMPORTANT: When you use the Convert To Bezier Path command to convert a parametric shape path to a Bezier shape path, the Bezier path that is created does not animate well (i.e., interpolation between paths behaves strangely and unpredictably). This is related to path direction and how transformations are stored. For now, you should not use these converted paths for animated paths (interpolation between paths); but, if you do want to try, you may be able to work around the issues by reversing the path before conversion.

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Todd Kopriva, Adobe Systems Incorporated
After Effects quality engineering
After Effects team blog
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