An ellipse with an equal width and height is a circle.

1.   rotate(radians(degree) );

1. float r=0;
2. 
   
3. void setup() {
4.   size(768, 576);
5.   background(0);
6.   smooth();
7.   noFill();
8.   stroke(random(255), random(255), random(255));
9. }
10. 
    
11. void draw() {
12.   translate(width*0.5, height*0.5);
13.   for (int i=0; i<360; i+=10) {
14.     float x = 50 + 133*sin(radians(i));
15.     float y = 20 + 133*cos(radians(i));   
16.     point (x, y);
17.   } // for
18. } // func

1. float r=0;
2. int j;
3. void setup() {
4.   size(768, 576);
5.   background(0);
6.   smooth();
7.   noFill();
8.   stroke(random(255), random(255), random(255));
9.   j=0;
10. }
11. void draw() {
12.   background (0);
13.   translate(width*0.5, height*0.5);
14.   int num = 1;
15.   for (int i=j; i<j+360; i+=10) {
16.     float x = 50 + 133*sin(radians(i));
17.     float y = 20 + 133*cos(radians(i));   
18.     point (x, y);
19.     stroke (num+100,2,2+num*11);
20.     rect (x, y,18,18);
21.     num++;
22.   } // for
23.     j++;
24. } // func

1. float r=0;
2. int j;
3. // both ArrayList must have the same number of members
4. ArrayList circle1;
5. ArrayList circle2;
6. void setup() {
7.   size(828, 622);
8.   background(0);
9.   smooth();
10.   noFill();
11.   stroke(random(255), random(255), random(255));
12.   // Create an empty ArrayList
13.   circle1 = new ArrayList();
14.   // Create an empty ArrayList
15.   circle2 = new ArrayList();
16.   // fill them separatly
17.   for (int i=j; i<j+360; i+=20) {
18.     float x = 0 + 133*sin(radians(i));
19.     float y = 0 + 133*cos(radians(i));
20.     // adding one element
21.     circle1.add(new PVector(x, y));
22.   }
23.   for (int i=j; i<j+360; i+=20) {
24.     float x = 0 + 273*sin(radians(i));
25.     float y = 0 + 273*cos(radians(i));
26.     // adding one element
27.     circle2.add(new PVector(x, y));
28.   }
29.   j=0;
30. }
31. void draw() {
32.   background (0);
33.   translate(width*0.5, height*0.5);
34.   int num = 1;
35.   // test: show points:
36.   for (int i = circle1.size()-1; i >= 0; i--) {
37.     // An ArrayList doesn't know what it is storing so we have to cast the object coming out
38.     PVector point1 = (PVector) circle1.get(i);
39.     stroke (num+100, 2, 2+num*11);
40.     point (point1.x, point1.y);
41.   }
42.   for (int i = circle2.size()-1; i >= 0; i--) {
43.     // An ArrayList doesn't know what it is storing so we have to cast the object coming out
44.     PVector point1 = (PVector) circle2.get(i);
45.     stroke (num+100, 2, 2+num*11);
46.     point (point1.x, point1.y);
47.   } 
48.   //
49.   // show the real thing
50.   num=0;
51.   pushMatrix();
52.   rotate(radians(j)); // makes the beast rotate
53.   //
54.   for (int i = circle1.size()-2; i >= 0; i--) {
55.     stroke (num+171, 2, 2+num*11);
56.     fill (num+1, 2, 2+num*11);   
57.     beginShape();
58.     vertex(((PVector) circle1.get(i)).x, ((PVector) circle1.get(i)).y);
59.     vertex(((PVector) circle2.get(i)).x, ((PVector) circle2.get(i)).y);
60.     vertex(((PVector) circle2.get(i+1)).x, ((PVector) circle2.get(i+1)).y);   
61.     vertex(((PVector) circle1.get(i+1)).x, ((PVector) circle1.get(i+1)).y);
62.     endShape(CLOSE);
63.     num++;
64.   } 
65.   // connect first and last pair
66.   int i=0; // first
67.   int last=  circle1.size()-1;  // last
68.   beginShape();
69.   vertex(((PVector) circle1.get(i)).x, ((PVector) circle1.get(i)).y);
70.   vertex(((PVector) circle2.get(i)).x, ((PVector) circle2.get(i)).y);
71.   vertex(((PVector) circle2.get(last)).x, ((PVector) circle2.get(last)).y);   
72.   vertex(((PVector) circle1.get(last)).x, ((PVector) circle1.get(last)).y);
73.   endShape(CLOSE);
74.   popMatrix();
75.   j++;
76. } // func