Dan Ebbert’s ferris wheel expression Add Gravity

[Mike Clasby]

Here is another Dan expression, hacked a bit to do what you want.

If you put a marker on the layer you want to rock, as if stopping I presume, the layer will rock with a dampening motion. This rock/dampening is added onto Dan’s original x Rotation Expression. This also goes on X Rotation of each car.

amp=70; //amplitude (pixels)
freq=2; //frequency (cycles per second)
decay=2.5; //decay time (seconds)

// find previous marker

n = 0; // assume haven’t reached a marker yet
if (marker.numKeys > 0){
n = marker.nearestKey(time).index;
if (marker.key(n).time > time){
n–;
}
}

if (n > 0) t = time – marker.key(n).time else t =0;
a = amp*Math.sin(freq*t*Math.PI*2)/Math.exp(decay*t);
-this_comp.layer(“Null 1”).rotationX + a

Change amp, freq, and decay as needed.

You can add markers on selected layers by hitting the * key on the numeric pad.

[David Rodriguez]

This expression only affects the layer it is applied to not the wheel as a whole, also I need to keep the “cars” oriented towards the camera so the rotation along the x axis is undesirable. I suppose an expression that was applied to each layer and was triggered by a marker COULD work..if it was applied to the position instead of the rotation, but I have no idea how to marry the existing expression for position with one that would do what I need it to.
The expression you posted was pretty nifty though!
Thanks for responding.

[Mike Clasby]

I guess I don’t really understand what you’re trying to do. I don’t understand why the X Rotation is undesirable, I followed the Dan Directions for setting up the Ferris Wheel and added a camera, I had to rotate that camera with the Orbit Tool, as the original setup when adding a camera was more like a TOP view, so I reoriented the camera. Maybe that’s where our misunderstanding lies, anyway…

Do you want the wheel to stop, a dampened stop, and all the cars react to that? If that’s what you want, put a Marker on the Null layer where you keyframe a stop, and put this expression on the Nulls’ X Rotation, and the wheel, well all the cars that make up the wheel, will dampen to a stop when that marker (Null) is hit:

amp=70; //amplitude (pixels)
freq=1; //frequency (cycles per second)
decay=2.5; //decay time (seconds)

// find previous marker

n = 0; // assume haven’t reached a marker yet
if (marker.numKeys > 0){
n = marker.nearestKey(time).index;
if (marker.key(n).time > time){
n–;
}
}

if (n > 0) t = time – marker.key(n).time else t =0;
a = amp*Math.sin(freq*t*Math.PI*2)/Math.exp(decay*t);
value + a

They still wont rock, their X rotation in reaction to the wheel as a whole stopping, so put this rotation on the X Rotation of each Car on the wheel:

amp=70; //amplitude (pixels)
freq=2; //frequency (cycles per second)
decay=2.5; //decay time (seconds)

// find previous marker

q = this_comp.layer(“Null 1”);
n = 0; // assume haven’t reached a marker yet
if (q.marker.numKeys > 0){
n = q.marker.nearestKey(time).index;
if (q.marker.key(n).time > time){
n–;
}
}

if (n > 0) t = time – q.marker.key(n).time else t =0;
a = amp*Math.sin(freq*t*Math.PI*2)/Math.exp(decay*t);
-this_comp.layer(“Null 1”).rotationX + a

Now each car will see the marker on the Null and rock/dampen to that.

[David Rodriguez]

You rock? Yes you do.
EXACTLY what I needed.

Thank You

[Mike Clasby]

Cool.