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Automating a simple ‘walk’ cycle
Hi,
I’m working on a project where I’m doing some very simple animation using 2D characters.
https://www.youtube.com/watch?v=a96Vzfi86cg
What I’m wanting to do is figure out how to automate a very simple ‘in/out/scissors’ style walk cycle when I move the character left or right.
I want the legs to rotate in and out like the video link above when I move the character’s position so the faster I move him, the faster his legs move, or the slower I move him, the more slowly they go.
It’s kind of like moving a car along the x-axis and having the wheels rotate around as it moves, but the wheels do that automatically.
Is this even possible?
Thanks,
Jim
Reel Inspirations – http://www.reelinspirations.com
Commercials, Dramas, Image Pieces, Documentaries, Motion Graphics -
5 Replies
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It’s hard to see the walk cycle in the linked video, but you should be able to set up a relationship between total horizontal distance moved and rotation angle. It’s hard to be more specific without knowing exactly what you’re trying to do.
Dan
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Here is a better example of what I’m after:
https://www.youtube.com/watch?v=3fKRxadmTjU&feature=youtu.be
Reel Inspirations – http://www.reelinspirations.com
Commercials, Dramas, Image Pieces, Documentaries, Motion Graphics -
This isn’t perfect, but I think it’s close. It assumes that the legs are parented to a layer named “body”, and body is keyframed to move horizontally. This would be the expression for rotation of the left (your left) leg:
body = thisComp.layer("body");
len = height; // length of leg
a = 15; // max angle
startX = body.transform.position.valueAtTime(inPoint)[0];
stride = 2*len*Math.sin(degreesToRadians(a));
d = (body.transform.position[0] - startX)%stride;
if (d < stride/2)
angle = radiansToDegrees(Math.asin(d/len))
else
angle = radiansToDegrees(Math.asin((stride -d)/len));
angle
For the right leg, just change the last line to :
-angle
Dan
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Dan, you are a genius. Wow, that math is crazy.
I have no idea what is going on (for the most part) but was able to adjust stride, etc. to get things working nicely.
I’m a former programmer (Actionscript, Javascript, database, etc.) but never did crazy math like that.
Way cool. Thanks so much!
Reel Inspirations – http://www.reelinspirations.com
Commercials, Dramas, Image Pieces, Documentaries, Motion Graphics -
The expression works pretty well.
But the “legs” won’t do the way back so the animation looks kinda jagged.
Anyone knows how to modify this?
Thanks in advance!
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