Wheel Rotation On/Off Controller

[Dan Ebberts]

I think the expression you need is a little more complicated than you might guess. Your expression needs to calculate the cumulative value up to the current frame. That is, it will need to look at the checkbox keyframes in the past and calculate the effect that “on” frames in the past have on wheel’s current value. The details depend on the nature of the your animation, but it can be done.

Dan

[Jaan Koppe]

Thanks for the Reply Dan!

For now I have an animation like this:

https://reels.creativecow.net/film/car-wheel-rotation-test

Both wheel rotations are driven by the Car’s x value.
And when the “Brake On” Checkbox is checked, then the First Wheel rotation value is simply 0.

So i am trying to give the first wheel a constant rotation value which is the current value of rotation. And when the “Brake On” is unchecked, then the Wheel Rotation follow’s the car position x again.

Jaan

[Dan Ebberts]

What’s the expression you’re using now?

Dan

[Jaan Koppe]

This is the first tyre Rotation expression:

if (comp("Main").layer("CarControl").effect("Break On")("Checkbox") == 0)
comp("Main").layer("Truck").transform.position[0]
else
0

[Dan Ebberts]

I’m surprised that works (as far as matching the tire rotation to the truck’s position). But since it does, you might be looking for something like this:


cb = comp("Main").layer("CarControl").effect("Break On")("Checkbox");
if (cb.value == 0){
comp("Main").layer("Truck").transform.position[0];
}else{
t = cb.nearestKey(time).time;
comp("Main").layer("Truck").transform.position.valueAtTime(t)[0];
}


Note that I have not tested this at all, so there are likely some problems with it, but hopefully it will be helpful.

Dan

[Dan Ebberts]

Sorry–I think I messed that up. It will probably be more like this (but it’s probably still not quite right):


cb = comp("Main").layer("CarControl").effect("Break On")("Checkbox");
if (cb.value == 0){
comp("Main").layer("Truck").transform.position[0];
}else{
n = cb.nearestKey(time).index;
if (time < cb.key(n).time) n--;
t = cb.key(n).time;
comp("Main").layer("Truck").transform.position.valueAtTime(t)[0];
}


Dan

[Jaan Koppe]

Thanks for the code Dan!

The breaking part works very good, until the brake will be “released”, then the wheel rotation value goes back to the car’s position value.

I think, that now I need to track the car’s position to get the current x value and apply that when the checkbox is unchecked?

I added a few lines to the code, got no error’s but also no result:

need to use some other approach I think 🙂

tx = comp("Main").layer("Truck").transform.position;
n2 = tx.nearestKey(time).index;
if (time < tx.key(n2).time) n2--;
t2 = tx.key(n2).time;

cb = comp("Main").layer("CarControl").effect("Break On")("Checkbox");
if (cb.value == 0){
tx.valueAtTime(t2)[0];
}else{
n = cb.nearestKey(time).index;
if (time < cb.key(n).time) n--;
t = cb.key(n).time;
comp("Main").layer("Truck").transform.position.valueAtTime(t)[0];
}