-
Dan Ebbert’s ferris wheel expression Add Gravity
I am using Dan Ebbert’s ferris wheel expression to create a parade of logos on a wheel…
**********************************************************
n = 15; // number of ferris wheel “cars”
r = 200; //radius of ferris wheela = degrees_to_radians(360/n)*(index-1);
x = 0;
z = r*Math.cos(a);
y = r*Math.sin(a);
[x,y,z]Create a null (“Null 1” in this example), move it to the bottom of the layer stack, make it 3D, make the null the parent of the video layers, and apply this expression for x rotation to each of the video layers:
-this_comp.layer(“Null 1”).rotationX
**********************************************************I have manually keyframed the rotation of the Null so that as each “car” passes in front of the camera it stops and swings back up a bit then continues on its way, it is as if the ferris wheel “car” hits an invisible “ground” and reacts for a moment then the “ground” disappears and the “cars” pick up speed and continue on their way until the next “car” hits the next invisible “ground”, kind of like a gravity bouncing ball effect.
Is there any way to have an expression that will do this for me?Many Thanks!
-
5 Replies
-
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 + aChange amp, freq, and decay as needed.
You can add markers on selected layers by hitting the * key on the numeric pad.
-
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. -
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 + aThey 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 + aNow each car will see the marker on the Null and rock/dampen to that.
-
You rock? Yes you do.
EXACTLY what I needed.Thank You
-
Cool.
Reply to this Discussion! Login or Sign Up