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Move object from one end of a SourceRectAtTime rectangle to the other over time
Tagged as “Basic”, but might not be.
I have a rectangle, the width of which is controlled by the SourceRectAtTime() of a text layer.
I also have a circle. At 0 frames, the circle needs to be at the left edge of the rectangle. at 25 frames, it needs to be at the right edge.
Regular keyframes obviously aren’t going to cut it because the rectangle can be any width.
I haven’t had to do do any expressions for about a year, so my brain has shut down. ?
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7 Replies
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Kieran! This is awesome! I love dynamic setups like this that can change based on other elements in the comp.
You will probably want to use linear() or ease() to accomplish this. It would look something like this:
L = thisComp.layer(“Shape Layer 1”); //Pickwhip the layer you are referencing
w = L.sourceRectAtTime().width * .5;
startPos = L.toComp(L.anchorPoint) – [w, 0];
endPos = L.toComp(L.anchorPoint) + [w, 0]
endFrame = framesToTime(25);
ease(time, 0, endFrame, startPos, endPos) // For a more harsh animation you could use linear() instead
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Haha! Hi, Trent. I’m glad you like it. Most of the stuff I’ve done in expressions has been for dynamic setups like text that can be of any length etc.
The following on the circle’s position almost works:-rectLeft = thisComp.layer(“rectangle”).sourceRectAtTime().left;
rectRight = thisComp.layer(“rectangle”).sourceRectAtTime().left + width;
easeOut(time,0,1,[rectLeft],[rectRight])
I’m going to try yours now.
EDIT: Forgot to mention that I’ve already separated the X and Y dimensions. I often find Position easier to work with like that if I only need to affect one dimension.
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Kieran,
You can also do a thing where you read the time of keyframes into the ease() expression start and end range. That allows you to change the length of the move by adjusting the position and distance between those keyframes.
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startPos = L.toComp(L.anchorPoint) – [w,0]; is giving me an “Invalid or unexpected token” error.
Currently investigating.
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There is something wrong with the formatting that is happening with the blog post. It’s a bit of a hassle, but try typing it instead of copy/paste. I had trouble with the quotes on the first line and then some character on the startPos line. Not sure what that’s about. 😐
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I’ve had to make a tiny tweak to startPos to make it fit around my own terrible scripting, but that’s done the trick. Thanks so much!
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You bet! Have fun with those expressions!
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