Starting in Processing 1.0, smoothing is always enabled with the OPENGL renderer setting. The smooth() and noSmooth() methods are ignored. See the hint() reference for information on disabling smoothing with OpenGL.

1. import processing.opengl.*;
2.  
3. void setup () {
4.   size(300, 200, OPENGL);
5. }
6.  
7. void draw () {
8.   background(0);
9.  
10.   strokeWeight(10);
11.   stroke(255);
12.   noFill();
13.   ellipse(0.25*width, 0.5*height, 100, 100);
14.  
15.   PVector v = new PVector(0.75*width, 0.5*height);
16.   noStroke();
17.   fill(255);
18.   drawRing(v, 45, 55, 100);
19. }
20.  
21. void drawRing(PVector v, float innerRad, float outerRad, int points) {
22.   float px = 0, py = 0, angle = 0;
23.   float rot = 360.0/points;
24.  
25.   beginShape(TRIANGLE_STRIP);
26.   for (int i=0; i<points; i++) {
27.     px = v.x + cos(radians(angle))*outerRad;
28.     py = v.y + sin(radians(angle))*outerRad;
29.     angle += rot;
30.     vertex(px, py);
31.     px = v.x + cos(radians(angle))*innerRad;
32.     py = v.y + sin(radians(angle))*innerRad;
33.     vertex(px, py);
34.     angle += rot;
35.   }
36.   endShape();
37. }

• In 1.5.1 there is a big difference between these two methods. One looks shit, the other smooth.
• In 2.0a6 there is no difference between these two methods. Both look mediocre.