Mask Path Shape to always match text total scale and width

Adobe After Effects Expressions

Mask Path Shape to always match text total scale and width

Posted by Craig Trayler on March 5, 2022 at 12:32 pm

Hi, I am looking for if possible, a way to have have a mask in a text layer always match the width and height of said text, and also the text will change over time.
I have seen some talk on linking mask points to positions of other things like nulls, but nothing solid that I can see that would link corner of a point to the top corner of source text.
I know there are ways with using a second mask layer, but I want this to all be done with one single Text layer.

Thanks in advance for any help.

Craig Trayler replied 4 years, 2 months ago 2 Members · 5 Replies
5 Replies

Filip Vandueren

March 5, 2022 at 1:49 pm

Hi Craig.

Give the mask this expression:

sr=sourceRectAtTime();
pts= [
	[sr.left, sr.top],
	[sr.left+sr.width, sr.top],
	[sr.left+sr.width, sr.top+sr.height],
	[sr.left, sr.top+sr.height],
];
createPath(pts,[],[],true);

Craig Trayler
March 5, 2022 at 3:35 pm

Hi Filip,
That is fantastic.
One more question if I may Filip;
if I wanted do to the same, but have the corners curved/rounded, would that be possible?
I would now guess you add in 4 extra points and space them out a small amount and then code in some kind of Bend between two points, maybe linked to a slider of some sort to adjust the bend/curve amount.

Filip Vandueren

March 5, 2022 at 4:53 pm

Correct, for example like this:

padding = 15;
rounding = 30;
curviness = 1; // 0=chamfer, 1=rounded
tangentLength = rounding * curviness*.55;
sr=sourceRectAtTime();
pts = [
	[sr.left-padding, sr.top-padding+rounding],
	[sr.left-padding+rounding, sr.top-padding],
	[sr.left+sr.width+padding-rounding, sr.top-padding],
	[sr.left+sr.width+padding, sr.top-padding+rounding],
	[sr.left+sr.width+padding, sr.top+sr.height+padding-rounding],
	[sr.left+sr.width+padding-rounding, sr.top+sr.height+padding],
	[sr.left-padding+rounding, sr.top+sr.height+padding],
	[sr.left-padding, sr.top+sr.height+padding-rounding],
];
in_Tangents = [
	[0,0],
	[-1,0]*tangentLength,
	[0,0],
	[0,-1]*tangentLength,
	[0,0],
	[1,0]*tangentLength,
	[0,0],
	[0,1]*tangentLength
];
out_Tangents = [
	[0,-1]*tangentLength,
	[0,0],
	[1,0]*tangentLength,
	[0,0],
	[0,1]*tangentLength,
	[0,0],
	[-1,0]*tangentLength,
	[0,0]
];
createPath(pts,in_Tangents,out_Tangents,true);

Filip Vandueren
March 5, 2022 at 4:54 pm

If you’re interested, here’s why there’s a multiplication by .55:

https://stackoverflow.com/questions/1734745/how-to-create-circle-with-b%C3%A9zier-curves
Craig Trayler
March 5, 2022 at 5:53 pm

Thank you again Filip, code works beautifully and I added some sliders for the padding and rounding. Also that link is a really nice read so far, thanks for that.
This opens many new doors for me. 🙏 – Craig

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