expression for sliding feet problem

[Fahd Chishty]

Provided that you are using a null object named “Foot Controller” and you want the floor to move back only when that null moves back, the following expression may help you.
Put it in the position of your floor.

temp = thisComp.layer("Foot_Controller").transform.position[0];
d=thisComp.frameDuration;
org=transform.position[1];
orgx=transform.position[0];
x=thisComp.layer("Foot_Controller").transform.position.valueAtTime(time-d)[0];

if(temp<=x)
{
[temp, org];
}
else
{
[orgx,org];
}


—
Fahd Chishty
Motion Design Artist
MotionCue

[Spiridon Mekas]

thank you Fahd!

Ae is giving me an error report in line 1 of the script though.

I’ll look into it, given that i’m a completely ignorant in anything concerning scripting it’s probably me doing something wrong..

Thanks!

[Fahd Chishty]

It may be giving you error because your Null object has a different name. If that is the case then replace “Foot_Controller” with the name your own Null object.

Or you can remove this statement “thisComp.layer(“Foot_Controller”).transform.position[0]” and pickwhip the X position of your controller

—
Fahd Chishty
Motion Design Artist
MotionCue

[Spiridon Mekas]

That was it, thanks for replying Fahd.

There is another problem though, related to my ignorance, of course. I didn’t take into account the fact that there is the other leg, and both legs go in cycle meaning that the foot first goes in one direction(horizontally) and then goes backwards(while the other moves forward) to complete a whole step cycle. The background goes backwards following the null of the first foot but then comes back as well.

I cannot imagine a workaround for this, guess i’ll have to do it the old pedestrian way, keyframing it all the way.

Thanks again!

[Fahd Chishty]

Actually when I was working on your problem last night, I thought of that issue too. I will work on it tonight again and then post the modified code.

—
Fahd Chishty
Motion Design Artist
MotionCue

[Spiridon Mekas]

Thank you!!

If it is any help, both feet have exact same motion. They are basically the same foot, one traced over the other just redrawn to appear as left and right foot and.

Here is one of the walks i animated if you could use the reference:

Many thanks!

[Fahd Chishty]

Do they both use the same Null or are there separate Nulls for both of them each?

—
Fahd Chishty
Motion Design Artist
MotionCue

[Spiridon Mekas]

So far i just did one null and i did’nt know how to set the background to follow two null objects. And also the null object could just follow the foot horizontally, which is the only relevant movement for the background.

[Spiridon Mekas]

what i do is manually keyframe the null following the left foot, from the first frame until it goes back, just before it lifts and starts going backwards, then i thought i could just copy the keyframes for any duration of the shot that is necessary. But the problem is that the movement is then delegated to the other leg whose position is exactly on the first keyframe.

[Fahd Chishty]

Dude! I have spent a lot of time on your problem, trying to solve it by expressions, but since After effects expressions have no way of storing a value, the floor jumps back to initial position once it has gone back with the foot.
I would suggest that you stick with the manual keyframes as they are easier to manipulate. Keyframe your floor to move back as each foot moves back.

In terms of expression, maybe Dan Ebberts can help. I raise my hands in defeat.

—
Fahd Chishty
Motion Design Artist
MotionCue