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Throw expression, but only for a set distance
I have to set up a ton of little tiny squares that move 10 pixels up in a semi-random order.
Right now I’m using two position keyframes… which works. But it’s kind of a hassle to make sure both keyframes are selected if I need to reposition them around the screen.
I ran into this “Throw” expression that moves a layer in one direction (left) into infinity.
// Throw (move at a constant speed without keyframes)
veloc = -10; //horizontal velocity (pixels per second)
x = position[0] + (time – inPoint) *veloc;
y = position[1];
[x,y]Is there a way to make it stop moving after a certain pixel distance? So I can place a square anywhere and it’ll move 10 pixels up beginning at its inPoint without any keyframes?
EDIT: on second look, this expression doesn’t seem to work either. Syntax error in line 3?
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8 Replies
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Some variation of this, probably:
veloc = -10;
maxPixels = 10;
x = position[0] + Math.max((time – inPoint)*veloc, -maxPixels);
y = position[1];
[x,y]Dan
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Fantastic (as always). Thank you Dan!!
PS: Check your email
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Hey Dan!
I’m using this today and I’m getting unreliable results. Sometimes the layer doesn’t move at all, and sometimes it infinitely moves, and sometimes it works perfectly.
In this case, I’m using veloc = 100 to move it up and veloc = -100 to move it down — which I think is the cause of the trouble… maybe?
veloc = -100;
maxPixels = 15;
x = position[0];
y = position[1] + Math.max((time – inPoint) * veloc, -maxPixels);
[x,y] -
This should work the way you’re using it (negative velocity to move down, positive to move up):
veloc = -100;
maxPixels = 15;
y = Math.min(maxPixels,(time – inPoint) * Math.abs(veloc)) * (veloc < 0 ? 1 : -1);
value + [0,y]Dan
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I think this is a little cleaner:
veloc = -100;
maxPixels = 15;
y = clamp((time – inPoint)*veloc,-maxPixels,maxPixels);
value – [0,y]Dan
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Hey Dan, I dusted off this expression and I’m getting a syntax error at line 3
// Throw (move at a constant speed without keyframes)
veloc = -10; //horizontal velocity (pixels per second)
x = position[0] + (time – inPoint) *veloc;
y = position[1];
[x,y]Has something changed in CC (2013)?
EDIT: I’m applying this to a Point Control effect.
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>Has something changed in CC (2013)?
Nothing that would effect that expression. Somehow you got the minus operator (-) replaced with a long dash. Just replace line 3 with this, and you should be good to go:
x = position[0] + (time – inPoint)*veloc;
Dan
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Wow, good eyes!
Must be Google Docs doing some sneaky en dash substitution.
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