Automatch matchmoved layer motionblur to source footage

[Redsandro]

[update]
Done, go here.
[/update]

I know it's supposed to be simple and I am ashamed I didn't figure it out yet

But what's the trick again to convert two 2d points to a rotation value? I want to convert a directional vector to a rotation value, and here's what I've got:

Code: Select all

// Get positions
Layer1 = thisComp.layer("PosLayer")
Pos1 = Layer1.toWorld(Layer1.anchorPoint);
Pos2 = Layer1.toWorld(Layer1.anchorPoint.valueAtTime(framesToTime(timeToFrames()-1)));
delta = Pos2 - Pos1;
radiansToDegrees(Math.atan2(delta[1],delta[0]));

But it's remaining at 0.. I am doing something wrong.

-edit-
Title changed to match content of this topic.

[Dan Ebberts]

Try this:

Layer1 = thisComp.layer("PosLayer")
Pos1 = Layer1.toWorld(Layer1.anchorPoint);
Pos2 = Layer1.toWorld(Layer1.anchorPoint,framesToTime(timeToFrames()-1));
delta = Pos2 - Pos1;
radiansToDegrees(Math.atan2(delta[1],delta[0]));

Dan

[Redsandro]

Great!
I didn't know .toWorld takes time as a second parameter. Thanks!

[Redsandro]

Made an expression to automatically match matchmoved layers' motionblur to the source footage's motion blur.
Simple idea but pretty awesome result imo.

Code: Select all

// Redsandro 2008-10-26
// effect("Directional Blur")("Direction")

// Position Source Layer (not parented)
lay = thisComp.layer("Tr Main Avg 1")

// Math
pos1 = lay.toWorld(lay.anchorPoint);
pos2 = lay.toWorld(lay.anchorPoint,framesToTime(timeToFrames()-1));
delta = pos2 - pos1;
radiansToDegrees(Math.atan2(delta[1],delta[0]))-90;

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// Redsandro 2008-10-26
// effect("Directional Blur")("Blur Length")

// Position Source Layer (not parented)
lay = thisComp.layer("Tr Main Avg 1");

// Get positions
pos1 = lay.transform.position;
pos2 = lay.transform.position.valueAtTime(framesToTime(timeToFrames()-1));

// Calculate length
len = pos1 - pos2;
len = Math.sqrt(len[0]*len[0]+len[1]*len[1]);

// Convert to descent blur length
len/3; // Eyeball-change to match footage blur length

[Redsandro]

I borrowed this part though, it's in all rotation calculating expressions around:

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radiansToDegrees(Math.atan2(x,y))

But I was wondering how to write this in code:

tan^-1(something)

because the inverse tangent of the quotient is already in degrees. I always try to figure this out until I find the Math.atan2 used somewhere on the net and to be honest I don't really get what it does. I like to stick to degrees. And the inverse tangent is universal, right? Or are only European calculators working in degrees?

[Dan Ebberts]

All the JavaScript trig functions work in radians. Math.atan() only takes one argument (the quotient of y/x) where Math.atan2() takes y and x separately. Also, I believe Math.atan2() can handle the case where x is 0.

Dan

[Redsandro]

Ah, that's why.

Actually I understand now that Math.atan(something) is similar to tan^-1(something).
Makes sense now