Polar coordinates does not respect collapse transformations?

[Balakay612]

Hi all,

Because I don't know of a way to have a gradient follow a stroke in AE (like you're able to do in AI, for example), I'm trying to fake it by creating a conic gradient (something else you can't do natively in AE!) using a standard linear Gradient Ramp and applying Polar Coordinates. This works all right, but when I bring my precomps (360x360) into my main comp (1080x1080), the polar coordinate effect only works if I don't check Collapse Transformations...except I have to, because I'm also using shape layers in my precomp(s) and I want everything continuously rasterized anyway.

What would be awesome is a) a native gradient along a stroke (I don't mean the gradient stroke option in a shape layer: as far as I'm aware, that still only allows you linear or circular gradients), which brings me to b) additional gradient models (like conic!)—at least I could more easily fake it with a real conic gradient.

Am I missing something? Anyone have any suggestions? Thanks!

[Rick Gerard]

Collapse transformations should not have any effect on a shape layer with a gradient fill. Here's everything done to both layers and as you can see CT is on and Rectangular to polar works just fine.

You don't even need to pre-compose. It also works if you apply the Gradient Fill effect. 

Show us a screenshot showing the modified properties of the layers that are giving you problems by selecting the layers, pressing 'uu', and embedding the screenshot using the toolbar. Do not use the Drag and Drop field. It's useless. I am lobbying to get it removed from the forum. 

[Roland Kahlenberg · Accepted solution]

You can use AE's Write-on Effect to create a Gradient Along A Path effect.

Here are the steps -

1) Create a Full-frame Solid and create a Mask Path to define your stroke path.

2) Select the Mask Path property and run the built-in script Create Nulls from Path (it's in the Scripts/ScriptsUI Panels folder)

3) When you're prompted with the script's UI, select the Trace Path option

4) A Null Object/Layer will be created and it will contain properties for Transform>Position, Transform>Rotation and an effect, Trace Path. The Trace Path property has a Progress parameter which defaults to 2 seconds. Set this time range to suit your needs. Disable the Loop checkbox if you don't need it.
5) Apply the effect, Effect>Generate>Write-on to the Solid you created in Step 1
6) Create an Expression to link the Write-On Effect's Brush Position property to the Transform>Position property of the Null Layer
7) Keyframe the Write-On's Color property and ensure Paint Time Properties is set to Color AND Paint Style is set to Transparent.

Here's an AEP in case you get lost, along the way.

http://www.broadcastGEMs.com/1765ghdgfhdfgJEW/broadcastGEMs_GradientAlong_StrokedPath.zip