-
Dan expression spring? Physic laws?
I have been using this expression from Dan Ebberts. It sort of work, but I wonder if it could calculate the velocity from the previous keyframe to the next keyframe and calculate how much the spring effect is been affected. Calculating the pixel/per second?
Extra thought: Wouldn’t be great to see a plug-in developped by Dan that mimics different the physics of law? I heard that Motion 2 does some of that, but I am an After Effects person…n = 0;
if (numKeys > 0){
n = nearestKey(time).index;
if (key(n).time > time){
n–;
}
}
if (n == 0){
value
}else{
t = time – key(n).time;
veloc = 12
amplitude = 330;
decay = 3;
y = amplitude*Math.cos(veloc*t)/Math.exp(decay*t);
value+[y,y,0];
} -
4 Replies
-
It sounds like you want something like the old Motion Math spring script. George Polevoy posted an expression a few years ago that works pretty well:
// AE expression by George Polevoy
// http://www.creativecow.net// attaches an object to a “Controller” object with a “spring”
// You need another “Controller” which will drive animation of this one// parameters
conserveMotion = 0.95; // valid range: 0.5 to 0.995
springResistance = 10; // positive values
prerollTime = 2; // value in seconds. greater values give more precise result//
fps = 1.0 / this_comp.frame_duration;
if ( prerollTime > time ) prerollTime = time;
dt = this_comp.frame_duration;
frame = time * fps;
integrationTime = time – prerollTime;s = [0,0];
p = this_comp.layer(“Controller”).position.value_at_time( integrationTime );i = frame – prerollTime * fps;
for (; i < frame; i++, integrationTime += dt ) { c = this_comp.layer("Controller").position.value_at_time( integrationTime ); d = c - p; s = s + d * springResistance; s = s * conserveMotion; p = p + s * dt; } Dan -
Hello Dan, thanks for answering.
It does not work well. tarting from keyframe ‘A’ to keyframe ‘B’, the layer behaves strangly, it sort of shakes. What I am looking for is a spring effect that occurs after the keyframe B is done calculated on the speed.
It seems like yours was closer to the answer. -
Did you try playing around with the “parameter” values?
conserveMotion = 0.95; // valid range: 0.5 to 0.995
springResistance = 10; // positive values -
I tried changing those numbers.
But it still doesn’t achieve the simple move from keyframe A to B with a spring effect after keyframe B.
I guess it’s not possible. 🙁
Reply to this Discussion! Login or Sign Up