Undertanding property speed

[Xavier Gomez]

Hi Miguel,
i tried and observed the same starting from third child.
It seems that AE needs some guiding otherwise it gets lost.
This expression seems to work fine:

curLayer = thisLayer;
multiplier = 1;
n=0;
do{
try {
driver = curLayer.effect("Driver")("Layer");
multiplier *= - driver.name.split("_")[1]/curLayer.name.split("_")[1];
curLayer = driver;
++n;
}
catch(e){driver = null;};
}while(driver!=null);
if (n===0) value else {
leadRot = curLayer.rotation;
thisLayer.rotation.valueAtTime(inPoint)-leadRot.valueAtTime(inPoint) + multiplier* (leadRot.value-leadRot.valueAtTime(inPoint));
};

Xavier

Xavier

[Xavier Gomez]

Hum, just realized that the expression works because i didnt put a Layer Control on the leading gear.
If you put one, you’ll get an infinite loop and a time out error.
It would be better to change the break condition to :

while(driver!=null && driver.name!==curLayer.name)

[Miguel De mendoza]

Thanks Xavier, it works perfect! Yes, it seems some stacking expression problem.

[Miguel De mendoza]

I Works for me like the first example. But I found another problema for the setup. I’m controling the speed of the lead gear with this expression:

thisComp.layer("Controls").effect("Master_Speed")("Slider") * time

Because I’m triggering the speed of the driver when I increase the speed of the Master_Speed with keyframes, the gears go so fast. So I need to implement an acceleration formula to the expression. I have the formula for acceleration:

deltaTime = 1/25;
iv = thisComp.layer("gear_5").transform.rotation.speedAtTime(time - deltaTime ); //Initial velocity
fv = thisComp.layer("gear_5").transform.rotation.speed; //Final velocity
(iv - fv)/dT

But I don’t know how to implement it on the expression. Any Idea?

[Miguel De mendoza]

Finally I found a simplest way to make all the teeth fint on the gears while moving. Simply I multiply the transmisión by the position of the driver:

driver = effect("Driver")("Layer");
nSplit =driver .name.split("_");
driverTeeth = nSplit[nSplit.length -1];
nSplit = name.split("_");
selfTeeth = nSplit[nSplit.length -1];
dSpeed = driver .transform.rotation;//.speed;
transmision = driverTeeth/selfTeeth;
dir = (driver.effect("Reversed")("Checkbox").value)? -1 : 1;
transmision *dSpeed * dir + value

It works for all the gears. I still have the problem with the acceleration. My Master gear rotation is driven by the expression :

thisComp.layer("Controls").effect("Master_Speed")("Slider") * time

But when I add keyframes to the slider to increase the speed, the gear start to rotate very fast till the interpolation ends. Is posible to get an incremental amount of the speed with keyframes on the slider?

[Xavier Gomez]

If the leading gear is driven by a speed slider, you should use for that gear an expression as explained in Dan’s website https://motionscript.com/articles/speed-control.html

For all other gears, i think that the expression i posted will work.

For these gears, you dont need a “inverse” checkbox, since a gear necesserily rotates the way opposite to its “parent”.
And the expression for these gears should not mention a “speed” variable either, otherwise you’ll need to integrate that speed, which can be super slow, and not necessary. (Overall, the rotation variation is a multiple of the rotation variation of the leader rotation, and that multiple is only determined by size ratios).

Xavier

[Miguel De mendoza]

Thanks Xavier, that was one of those posts that I read time ago and I forget XD. Pretty usefull!