give these a try:

http://processing.org/learning/basics/bezier.html

http://processing.org/reference/bezier_.html

F

it's still vague for me.
anyway i'll try.
thanks fjen.

You could draw an ellipse,
using
ellipse(x, y, width, height)
and also
ellipseMode(), stroke(), fill(), noFill(), color(), etc...

put the ellipse inside a loop, (the draw() loop itself or another inner loop),
then on each iteration, update some/many/all of the parameters:
x=x+deltax or x=fx(t)
y=y+deltay or y=fy(t)
width=...
height=...
color=...
alpha=...

You can use cyclic functions like sin(), cos() ...

Run the following, then change it:

int n=800;//image size
int margin=8;
float n2,n4;

void setup() {
 int nn=n-2*margin;
 n2=nn/2.00;
 n4=nn/4.00;
 int maxWidth=n;
 int maxHeight=n;
 size(n,n);
 background(0);
 noFill();
 ellipseMode(CENTER);
 noLoop();
}

void draw() {
 int r,g,b,a;
 float x,y,w,h;
 //initial color
 r=0;
 g=100;
 b=200;
 a=30;
 for (int t = 0; t < 2000; t++) {
   float tt=t*TWO_PI/500;
   //change color
   r=(r+10)%255;
   g=(g+15)%255;
   b=(b+20)%255;
   //a=(a+2)%50;
   stroke(r,g,b,a);
   //set center x,y
   x=margin+n4+n4*(1+sin(2.0*tt));
   y=margin+n4+n4*(1+cos(1.0*tt));
   //set width,height
   w=n2*sin(2.0*tt);
   h=n2*cos(1.0*tt);
   //draw ellipse
   ellipse(x, y, w, h);
 }//for

}