Converting old motion math preset into expression

Adobe After Effects Expressions

Converting old motion math preset into expression

Posted by J2m on October 10, 2005 at 5:24 pm

Hi all,

I need to use the old “spring” motion math preset in AE 6.5. Unfortunately, I’m extremely lame in understanding Java script logic. The .MM format cannot be imported in AE any more, and the text within it can’t be imported as an expression AS IT IS.

Is there any way to easily convert this text so that it can be imported as an expression ?

Sorry if the answer is obvious to you guys, but I just can’t figure it out by myself…

Thanks a lot to anyone who can help !

Just in case, here is the text content of the old .MM file :

// One spring – version 1.2

// This script attaches a spring between the 2 layers shown in the popups.
// Layer 1 keeps its original motion, while layer 2 is attached by a spring to it.

// LAYER PROPERTY CHANNEL
// —— ———- ——–
// 1: Layer that moves doesn’t matter doesn’t matter
// 2: Layer attached to #1 by a spring doesn’t matter doesn’t matter

if (time() == start_time) {
rest_length = 10; // rest length of spring in pixels
damp = 0.95; // Damping (0 = infinite friction, 1 = none)

p1 = value(pop_layer(1), position);
p2 = value(pop_layer(2), position);

last_p1 = tmap(time() – step_time, value(pop_layer(1), position));
last_p2 = tmap(time() – step_time, value(pop_layer(2), position));

v1 = (p1 – last_p1);
v2 = (p2 – last_p2);
} else {
p1 = value(pop_layer(1), position);

delta = p2 – p1;
n_delta = normalize(delta);

a = 2 * n_delta * (length(delta) – rest_length) * step_time;

v2 = (v2 – a) * damp;
v1 = (v1 + a) * damp;

p1 = p1 + v1;
p2 = p2 + v2;
}
value(pop_layer(2), position) = p2;

J2m replied 20 years, 11 months ago 2 Members · 2 Replies
2 Replies

Dan Ebberts
October 10, 2005 at 5:37 pm

See the 10/7 thread “expression with springs”.

Dan
J2m
October 10, 2005 at 6:38 pm

Oooops… I usually check the forum before posting, but this was such a specific problem that I wouldn’t have guessed someone else posted the same thing, and two days ago, no less !

Thanks a lot for you reply. I must confess I didn’t expect to get one so soon. And your expression seems to do the trick, too.

But it doesn’t change the fact that something has been lost with the removal of Motion Math. Expressions don’t replace it entirely. I don’t see why the Adobe team didn’t leave it there, especially since we still have the simple text effect in 6.5…!

Anyway, thanks again.

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