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Leaf falling expression (how do i get it to delay?)
Hi
i adapted one of Dan Ebberts tutorials to make a leaf fall from a tree. i’m really happy with it but i need it to start later than right at the beginning… and i’m having trouble doing that.
I’ve posted the expressions below.
i’m quite new to AE expressions… any help will probably save me hours of trying to struggle with it myself.
Thanks
Simon
so this is what i have…
there is a null layer and on the image of the leaf there are these expressions…
The Point Effect (renamed ‘Life’)
lmin = 1.5; //minimum particle life
lmax = 3; //maximum particle lifeseed_random(1,true);
life=random(lmin,lmax);
birth=0;
[birth,life]Postition
gmin=20; //gravity
gmax=70;
w=20; //wind
wdir=0; //wind direction (0 = from left)
vmin=100; //minimum initial velocity
vmax=300; //maximum initial velocity
amin=30; //minimum launch angle from vertical
amax=120; //maximum launch angle from vertical
d=2; //drag coeffecientbirth=effect(“life”).param(“Point”)[0];
life=effect(“life”).param(“Point”)[1];
origin=[position[0],position[1],position[2]];
age=time-birth;
seed_random(1,true);
s=random(vmin,vmax);//initial speed
g=random(gmin,gmax);
v_e=this_comp.layer(“Null 1”).position.velocity_at_time(birth); //emitter velocity
a=degrees_to_radians(random(amin,amax)); //angle from vertical
r=degrees_to_radians(random(360)) //rotation around y axis
x=s*Math.sin(a)*Math.cos(r);
y=-s*Math.cos(a);
z=s*Math.sin(a)*Math.sin(r);
v=[x,y,z]+v_e;
new_speed=length(v);
unit_v=normalize(v);if (d>0){
delta_p=new_speed*(1-Math.exp(-d*age))/d;
}else{
delta_p=age*new_speed;
}
delta_w=w*age;
delta_g=g*age*age/2;wa=degrees_to_radians(wdir);
origin + delta_p*unit_v + [delta_w*Math.cos(wa),0,delta_w*Math.sin(wa)] + [0,delta_g,0]
Orientation
rmax=0;
rmin=-0;
birth=effect(“life”).param(“Point”)[0];
life=effect(“life”).param(“Point”)[1];
age=time-birth;
if (life==0){
[0,0,0]
}else{
seed_random(birth,true);
init_orient=random([360,360,360]);
final_orient=(init_orient);
init_orient +(final_orient-init_orient)*(age/life)
}X Rotation
rmax=360; //maximum rotation
rmin=-360; //minimum rotationbirth=effect(“life”).param(“Point”)[0];
seed_random(1,true);
r=random(rmin,rmax);
life=effect(“life”).param(“Point”)[1];
age=time-birth;
if(life==0){
0
}else{
r/life*age
}Y Rotation
rmax=360; //maximum rotation
rmin=-360; //minimum rotationbirth=effect(“life”).param(“Point”)[0];
seed_random(1,true);
r=random(rmin,rmax);
life=effect(“life”).param(“Point”)[1];
age=time-birth;
if(life==0){
0
}else{
r/life*age
}Z Rotation
rmax=360; //maximum rotation
rmin=-360; //minimum rotationbirth=effect(“life”).param(“Point”)[0];
seed_random(1,true);
r=random(rmin,rmax);
life=effect(“life”).param(“Point”)[1];
age=time-birth;
if(life==0){
0
}else{
r/life*age
} -
2 Replies
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I think all you need to do is change the birth variable in the point control expression and then add some code to each of the other expressions that checks to see if the current time is less than birth, in which case the expression does nothing.
Here’s an example of a random birth expression for the point control:
bmin = 0; // minimum birth time
bmax = 4; // maximum birth time
lmin = 1.5; //minimum particle life
lmax = 3; //maximum particle lifeseed_random(1,true);
life=random(lmin,lmax);
birth=random(bmin,bmax);
[birth,life]And here’s the z rotation expression modification to get you started:
Z Rotation
rmax=360; //maximum rotation
rmin=-360; //minimum rotationbirth=effect(“life”).param(“Point”)[0];
seed_random(1,true);
r=random(rmin,rmax);
life=effect(“life”).param(“Point”)[1];
if (time >= birth){ //***** this is new
age=time-birth;
if(life==0){
0
}else{
r/life*age
}
}else{ // **** this is new
value // **** this is new
} // **** this is newDan
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ah…. amazing!
thats perfect.
thanks very much!
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